| /* |
| * fs/dcache.c |
| * |
| * Complete reimplementation |
| * (C) 1997 Thomas Schoebel-Theuer, |
| * with heavy changes by Linus Torvalds |
| */ |
| |
| /* |
| * Notes on the allocation strategy: |
| * |
| * The dcache is a master of the icache - whenever a dcache entry |
| * exists, the inode will always exist. "iput()" is done either when |
| * the dcache entry is deleted or garbage collected. |
| */ |
| |
| #include <linux/syscalls.h> |
| #include <linux/string.h> |
| #include <linux/mm.h> |
| #include <linux/fs.h> |
| #include <linux/fsnotify.h> |
| #include <linux/slab.h> |
| #include <linux/init.h> |
| #include <linux/hash.h> |
| #include <linux/cache.h> |
| #include <linux/export.h> |
| #include <linux/mount.h> |
| #include <linux/file.h> |
| #include <asm/uaccess.h> |
| #include <linux/security.h> |
| #include <linux/seqlock.h> |
| #include <linux/swap.h> |
| #include <linux/bootmem.h> |
| #include <linux/fs_struct.h> |
| #include <linux/hardirq.h> |
| #include <linux/bit_spinlock.h> |
| #include <linux/rculist_bl.h> |
| #include <linux/prefetch.h> |
| #include <linux/ratelimit.h> |
| #include <linux/list_lru.h> |
| #include "internal.h" |
| #include "mount.h" |
| |
| /* |
| * Usage: |
| * dcache->d_inode->i_lock protects: |
| * - i_dentry, d_alias, d_inode of aliases |
| * dcache_hash_bucket lock protects: |
| * - the dcache hash table |
| * s_anon bl list spinlock protects: |
| * - the s_anon list (see __d_drop) |
| * dentry->d_sb->s_dentry_lru_lock protects: |
| * - the dcache lru lists and counters |
| * d_lock protects: |
| * - d_flags |
| * - d_name |
| * - d_lru |
| * - d_count |
| * - d_unhashed() |
| * - d_parent and d_subdirs |
| * - childrens' d_child and d_parent |
| * - d_alias, d_inode |
| * |
| * Ordering: |
| * dentry->d_inode->i_lock |
| * dentry->d_lock |
| * dentry->d_sb->s_dentry_lru_lock |
| * dcache_hash_bucket lock |
| * s_anon lock |
| * |
| * If there is an ancestor relationship: |
| * dentry->d_parent->...->d_parent->d_lock |
| * ... |
| * dentry->d_parent->d_lock |
| * dentry->d_lock |
| * |
| * If no ancestor relationship: |
| * if (dentry1 < dentry2) |
| * dentry1->d_lock |
| * dentry2->d_lock |
| */ |
| int sysctl_vfs_cache_pressure __read_mostly = 100; |
| EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); |
| |
| __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); |
| |
| EXPORT_SYMBOL(rename_lock); |
| |
| static struct kmem_cache *dentry_cache __read_mostly; |
| |
| /* |
| * This is the single most critical data structure when it comes |
| * to the dcache: the hashtable for lookups. Somebody should try |
| * to make this good - I've just made it work. |
| * |
| * This hash-function tries to avoid losing too many bits of hash |
| * information, yet avoid using a prime hash-size or similar. |
| */ |
| |
| static unsigned int d_hash_mask __read_mostly; |
| static unsigned int d_hash_shift __read_mostly; |
| |
| static struct hlist_bl_head *dentry_hashtable __read_mostly; |
| |
| static inline struct hlist_bl_head *d_hash(const struct dentry *parent, |
| unsigned int hash) |
| { |
| hash += (unsigned long) parent / L1_CACHE_BYTES; |
| hash = hash + (hash >> d_hash_shift); |
| return dentry_hashtable + (hash & d_hash_mask); |
| } |
| |
| /* Statistics gathering. */ |
| struct dentry_stat_t dentry_stat = { |
| .age_limit = 45, |
| }; |
| |
| static DEFINE_PER_CPU(long, nr_dentry); |
| static DEFINE_PER_CPU(long, nr_dentry_unused); |
| |
| #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) |
| |
| /* |
| * Here we resort to our own counters instead of using generic per-cpu counters |
| * for consistency with what the vfs inode code does. We are expected to harvest |
| * better code and performance by having our own specialized counters. |
| * |
| * Please note that the loop is done over all possible CPUs, not over all online |
| * CPUs. The reason for this is that we don't want to play games with CPUs going |
| * on and off. If one of them goes off, we will just keep their counters. |
| * |
| * glommer: See cffbc8a for details, and if you ever intend to change this, |
| * please update all vfs counters to match. |
| */ |
| static long get_nr_dentry(void) |
| { |
| int i; |
| long sum = 0; |
| for_each_possible_cpu(i) |
| sum += per_cpu(nr_dentry, i); |
| return sum < 0 ? 0 : sum; |
| } |
| |
| static long get_nr_dentry_unused(void) |
| { |
| int i; |
| long sum = 0; |
| for_each_possible_cpu(i) |
| sum += per_cpu(nr_dentry_unused, i); |
| return sum < 0 ? 0 : sum; |
| } |
| |
| int proc_nr_dentry(ctl_table *table, int write, void __user *buffer, |
| size_t *lenp, loff_t *ppos) |
| { |
| dentry_stat.nr_dentry = get_nr_dentry(); |
| dentry_stat.nr_unused = get_nr_dentry_unused(); |
| return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| } |
| #endif |
| |
| /* |
| * Compare 2 name strings, return 0 if they match, otherwise non-zero. |
| * The strings are both count bytes long, and count is non-zero. |
| */ |
| #ifdef CONFIG_DCACHE_WORD_ACCESS |
| |
| #include <asm/word-at-a-time.h> |
| /* |
| * NOTE! 'cs' and 'scount' come from a dentry, so it has a |
| * aligned allocation for this particular component. We don't |
| * strictly need the load_unaligned_zeropad() safety, but it |
| * doesn't hurt either. |
| * |
| * In contrast, 'ct' and 'tcount' can be from a pathname, and do |
| * need the careful unaligned handling. |
| */ |
| static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) |
| { |
| unsigned long a,b,mask; |
| |
| for (;;) { |
| a = *(unsigned long *)cs; |
| b = load_unaligned_zeropad(ct); |
| if (tcount < sizeof(unsigned long)) |
| break; |
| if (unlikely(a != b)) |
| return 1; |
| cs += sizeof(unsigned long); |
| ct += sizeof(unsigned long); |
| tcount -= sizeof(unsigned long); |
| if (!tcount) |
| return 0; |
| } |
| mask = bytemask_from_count(tcount); |
| return unlikely(!!((a ^ b) & mask)); |
| } |
| |
| #else |
| |
| static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) |
| { |
| do { |
| if (*cs != *ct) |
| return 1; |
| cs++; |
| ct++; |
| tcount--; |
| } while (tcount); |
| return 0; |
| } |
| |
| #endif |
| |
| static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount) |
| { |
| const unsigned char *cs; |
| /* |
| * Be careful about RCU walk racing with rename: |
| * use ACCESS_ONCE to fetch the name pointer. |
| * |
| * NOTE! Even if a rename will mean that the length |
| * was not loaded atomically, we don't care. The |
| * RCU walk will check the sequence count eventually, |
| * and catch it. And we won't overrun the buffer, |
| * because we're reading the name pointer atomically, |
| * and a dentry name is guaranteed to be properly |
| * terminated with a NUL byte. |
| * |
| * End result: even if 'len' is wrong, we'll exit |
| * early because the data cannot match (there can |
| * be no NUL in the ct/tcount data) |
| */ |
| cs = ACCESS_ONCE(dentry->d_name.name); |
| smp_read_barrier_depends(); |
| return dentry_string_cmp(cs, ct, tcount); |
| } |
| |
| static void __d_free(struct rcu_head *head) |
| { |
| struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); |
| |
| WARN_ON(!hlist_unhashed(&dentry->d_alias)); |
| if (dname_external(dentry)) |
| kfree(dentry->d_name.name); |
| kmem_cache_free(dentry_cache, dentry); |
| } |
| |
| /* |
| * no locks, please. |
| */ |
| static void d_free(struct dentry *dentry) |
| { |
| BUG_ON((int)dentry->d_lockref.count > 0); |
| this_cpu_dec(nr_dentry); |
| if (dentry->d_op && dentry->d_op->d_release) |
| dentry->d_op->d_release(dentry); |
| |
| /* if dentry was never visible to RCU, immediate free is OK */ |
| if (!(dentry->d_flags & DCACHE_RCUACCESS)) |
| __d_free(&dentry->d_u.d_rcu); |
| else |
| call_rcu(&dentry->d_u.d_rcu, __d_free); |
| } |
| |
| /** |
| * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups |
| * @dentry: the target dentry |
| * After this call, in-progress rcu-walk path lookup will fail. This |
| * should be called after unhashing, and after changing d_inode (if |
| * the dentry has not already been unhashed). |
| */ |
| static inline void dentry_rcuwalk_barrier(struct dentry *dentry) |
| { |
| assert_spin_locked(&dentry->d_lock); |
| /* Go through a barrier */ |
| write_seqcount_barrier(&dentry->d_seq); |
| } |
| |
| /* |
| * Release the dentry's inode, using the filesystem |
| * d_iput() operation if defined. Dentry has no refcount |
| * and is unhashed. |
| */ |
| static void dentry_iput(struct dentry * dentry) |
| __releases(dentry->d_lock) |
| __releases(dentry->d_inode->i_lock) |
| { |
| struct inode *inode = dentry->d_inode; |
| if (inode) { |
| dentry->d_inode = NULL; |
| hlist_del_init(&dentry->d_alias); |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&inode->i_lock); |
| if (!inode->i_nlink) |
| fsnotify_inoderemove(inode); |
| if (dentry->d_op && dentry->d_op->d_iput) |
| dentry->d_op->d_iput(dentry, inode); |
| else |
| iput(inode); |
| } else { |
| spin_unlock(&dentry->d_lock); |
| } |
| } |
| |
| /* |
| * Release the dentry's inode, using the filesystem |
| * d_iput() operation if defined. dentry remains in-use. |
| */ |
| static void dentry_unlink_inode(struct dentry * dentry) |
| __releases(dentry->d_lock) |
| __releases(dentry->d_inode->i_lock) |
| { |
| struct inode *inode = dentry->d_inode; |
| __d_clear_type(dentry); |
| dentry->d_inode = NULL; |
| hlist_del_init(&dentry->d_alias); |
| dentry_rcuwalk_barrier(dentry); |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&inode->i_lock); |
| if (!inode->i_nlink) |
| fsnotify_inoderemove(inode); |
| if (dentry->d_op && dentry->d_op->d_iput) |
| dentry->d_op->d_iput(dentry, inode); |
| else |
| iput(inode); |
| } |
| |
| /* |
| * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry |
| * is in use - which includes both the "real" per-superblock |
| * LRU list _and_ the DCACHE_SHRINK_LIST use. |
| * |
| * The DCACHE_SHRINK_LIST bit is set whenever the dentry is |
| * on the shrink list (ie not on the superblock LRU list). |
| * |
| * The per-cpu "nr_dentry_unused" counters are updated with |
| * the DCACHE_LRU_LIST bit. |
| * |
| * These helper functions make sure we always follow the |
| * rules. d_lock must be held by the caller. |
| */ |
| #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x)) |
| static void d_lru_add(struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, 0); |
| dentry->d_flags |= DCACHE_LRU_LIST; |
| this_cpu_inc(nr_dentry_unused); |
| WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru)); |
| } |
| |
| static void d_lru_del(struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
| dentry->d_flags &= ~DCACHE_LRU_LIST; |
| this_cpu_dec(nr_dentry_unused); |
| WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru)); |
| } |
| |
| static void d_shrink_del(struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST); |
| list_del_init(&dentry->d_lru); |
| dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST); |
| this_cpu_dec(nr_dentry_unused); |
| } |
| |
| static void d_shrink_add(struct dentry *dentry, struct list_head *list) |
| { |
| D_FLAG_VERIFY(dentry, 0); |
| list_add(&dentry->d_lru, list); |
| dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST; |
| this_cpu_inc(nr_dentry_unused); |
| } |
| |
| /* |
| * These can only be called under the global LRU lock, ie during the |
| * callback for freeing the LRU list. "isolate" removes it from the |
| * LRU lists entirely, while shrink_move moves it to the indicated |
| * private list. |
| */ |
| static void d_lru_isolate(struct dentry *dentry) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
| dentry->d_flags &= ~DCACHE_LRU_LIST; |
| this_cpu_dec(nr_dentry_unused); |
| list_del_init(&dentry->d_lru); |
| } |
| |
| static void d_lru_shrink_move(struct dentry *dentry, struct list_head *list) |
| { |
| D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST); |
| dentry->d_flags |= DCACHE_SHRINK_LIST; |
| list_move_tail(&dentry->d_lru, list); |
| } |
| |
| /* |
| * dentry_lru_(add|del)_list) must be called with d_lock held. |
| */ |
| static void dentry_lru_add(struct dentry *dentry) |
| { |
| if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) |
| d_lru_add(dentry); |
| } |
| |
| /* |
| * Remove a dentry with references from the LRU. |
| * |
| * If we are on the shrink list, then we can get to try_prune_one_dentry() and |
| * lose our last reference through the parent walk. In this case, we need to |
| * remove ourselves from the shrink list, not the LRU. |
| */ |
| static void dentry_lru_del(struct dentry *dentry) |
| { |
| if (dentry->d_flags & DCACHE_LRU_LIST) { |
| if (dentry->d_flags & DCACHE_SHRINK_LIST) |
| return d_shrink_del(dentry); |
| d_lru_del(dentry); |
| } |
| } |
| |
| /** |
| * d_kill - kill dentry and return parent |
| * @dentry: dentry to kill |
| * @parent: parent dentry |
| * |
| * The dentry must already be unhashed and removed from the LRU. |
| * |
| * If this is the root of the dentry tree, return NULL. |
| * |
| * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by |
| * d_kill. |
| */ |
| static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent) |
| __releases(dentry->d_lock) |
| __releases(parent->d_lock) |
| __releases(dentry->d_inode->i_lock) |
| { |
| list_del(&dentry->d_u.d_child); |
| /* |
| * Inform d_walk() that we are no longer attached to the |
| * dentry tree |
| */ |
| dentry->d_flags |= DCACHE_DENTRY_KILLED; |
| if (parent) |
| spin_unlock(&parent->d_lock); |
| dentry_iput(dentry); |
| /* |
| * dentry_iput drops the locks, at which point nobody (except |
| * transient RCU lookups) can reach this dentry. |
| */ |
| d_free(dentry); |
| return parent; |
| } |
| |
| /** |
| * d_drop - drop a dentry |
| * @dentry: dentry to drop |
| * |
| * d_drop() unhashes the entry from the parent dentry hashes, so that it won't |
| * be found through a VFS lookup any more. Note that this is different from |
| * deleting the dentry - d_delete will try to mark the dentry negative if |
| * possible, giving a successful _negative_ lookup, while d_drop will |
| * just make the cache lookup fail. |
| * |
| * d_drop() is used mainly for stuff that wants to invalidate a dentry for some |
| * reason (NFS timeouts or autofs deletes). |
| * |
| * __d_drop requires dentry->d_lock. |
| */ |
| void __d_drop(struct dentry *dentry) |
| { |
| if (!d_unhashed(dentry)) { |
| struct hlist_bl_head *b; |
| /* |
| * Hashed dentries are normally on the dentry hashtable, |
| * with the exception of those newly allocated by |
| * d_obtain_alias, which are always IS_ROOT: |
| */ |
| if (unlikely(IS_ROOT(dentry))) |
| b = &dentry->d_sb->s_anon; |
| else |
| b = d_hash(dentry->d_parent, dentry->d_name.hash); |
| |
| hlist_bl_lock(b); |
| __hlist_bl_del(&dentry->d_hash); |
| dentry->d_hash.pprev = NULL; |
| hlist_bl_unlock(b); |
| dentry_rcuwalk_barrier(dentry); |
| } |
| } |
| EXPORT_SYMBOL(__d_drop); |
| |
| void d_drop(struct dentry *dentry) |
| { |
| spin_lock(&dentry->d_lock); |
| __d_drop(dentry); |
| spin_unlock(&dentry->d_lock); |
| } |
| EXPORT_SYMBOL(d_drop); |
| |
| /* |
| * Finish off a dentry we've decided to kill. |
| * dentry->d_lock must be held, returns with it unlocked. |
| * If ref is non-zero, then decrement the refcount too. |
| * Returns dentry requiring refcount drop, or NULL if we're done. |
| */ |
| static struct dentry * |
| dentry_kill(struct dentry *dentry, int unlock_on_failure) |
| __releases(dentry->d_lock) |
| { |
| struct inode *inode; |
| struct dentry *parent; |
| |
| inode = dentry->d_inode; |
| if (inode && !spin_trylock(&inode->i_lock)) { |
| relock: |
| if (unlock_on_failure) { |
| spin_unlock(&dentry->d_lock); |
| cpu_relax(); |
| } |
| return dentry; /* try again with same dentry */ |
| } |
| if (IS_ROOT(dentry)) |
| parent = NULL; |
| else |
| parent = dentry->d_parent; |
| if (parent && !spin_trylock(&parent->d_lock)) { |
| if (inode) |
| spin_unlock(&inode->i_lock); |
| goto relock; |
| } |
| |
| /* |
| * The dentry is now unrecoverably dead to the world. |
| */ |
| lockref_mark_dead(&dentry->d_lockref); |
| |
| /* |
| * inform the fs via d_prune that this dentry is about to be |
| * unhashed and destroyed. |
| */ |
| if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry)) |
| dentry->d_op->d_prune(dentry); |
| |
| dentry_lru_del(dentry); |
| /* if it was on the hash then remove it */ |
| __d_drop(dentry); |
| return d_kill(dentry, parent); |
| } |
| |
| /* |
| * This is dput |
| * |
| * This is complicated by the fact that we do not want to put |
| * dentries that are no longer on any hash chain on the unused |
| * list: we'd much rather just get rid of them immediately. |
| * |
| * However, that implies that we have to traverse the dentry |
| * tree upwards to the parents which might _also_ now be |
| * scheduled for deletion (it may have been only waiting for |
| * its last child to go away). |
| * |
| * This tail recursion is done by hand as we don't want to depend |
| * on the compiler to always get this right (gcc generally doesn't). |
| * Real recursion would eat up our stack space. |
| */ |
| |
| /* |
| * dput - release a dentry |
| * @dentry: dentry to release |
| * |
| * Release a dentry. This will drop the usage count and if appropriate |
| * call the dentry unlink method as well as removing it from the queues and |
| * releasing its resources. If the parent dentries were scheduled for release |
| * they too may now get deleted. |
| */ |
| void dput(struct dentry *dentry) |
| { |
| if (unlikely(!dentry)) |
| return; |
| |
| repeat: |
| if (lockref_put_or_lock(&dentry->d_lockref)) |
| return; |
| |
| /* Unreachable? Get rid of it */ |
| if (unlikely(d_unhashed(dentry))) |
| goto kill_it; |
| |
| if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) { |
| if (dentry->d_op->d_delete(dentry)) |
| goto kill_it; |
| } |
| |
| if (!(dentry->d_flags & DCACHE_REFERENCED)) |
| dentry->d_flags |= DCACHE_REFERENCED; |
| dentry_lru_add(dentry); |
| |
| dentry->d_lockref.count--; |
| spin_unlock(&dentry->d_lock); |
| return; |
| |
| kill_it: |
| dentry = dentry_kill(dentry, 1); |
| if (dentry) |
| goto repeat; |
| } |
| EXPORT_SYMBOL(dput); |
| |
| /** |
| * d_invalidate - invalidate a dentry |
| * @dentry: dentry to invalidate |
| * |
| * Try to invalidate the dentry if it turns out to be |
| * possible. If there are other dentries that can be |
| * reached through this one we can't delete it and we |
| * return -EBUSY. On success we return 0. |
| * |
| * no dcache lock. |
| */ |
| |
| int d_invalidate(struct dentry * dentry) |
| { |
| /* |
| * If it's already been dropped, return OK. |
| */ |
| spin_lock(&dentry->d_lock); |
| if (d_unhashed(dentry)) { |
| spin_unlock(&dentry->d_lock); |
| return 0; |
| } |
| /* |
| * Check whether to do a partial shrink_dcache |
| * to get rid of unused child entries. |
| */ |
| if (!list_empty(&dentry->d_subdirs)) { |
| spin_unlock(&dentry->d_lock); |
| shrink_dcache_parent(dentry); |
| spin_lock(&dentry->d_lock); |
| } |
| |
| /* |
| * Somebody else still using it? |
| * |
| * If it's a directory, we can't drop it |
| * for fear of somebody re-populating it |
| * with children (even though dropping it |
| * would make it unreachable from the root, |
| * we might still populate it if it was a |
| * working directory or similar). |
| * We also need to leave mountpoints alone, |
| * directory or not. |
| */ |
| if (dentry->d_lockref.count > 1 && dentry->d_inode) { |
| if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) { |
| spin_unlock(&dentry->d_lock); |
| return -EBUSY; |
| } |
| } |
| |
| __d_drop(dentry); |
| spin_unlock(&dentry->d_lock); |
| return 0; |
| } |
| EXPORT_SYMBOL(d_invalidate); |
| |
| /* This must be called with d_lock held */ |
| static inline void __dget_dlock(struct dentry *dentry) |
| { |
| dentry->d_lockref.count++; |
| } |
| |
| static inline void __dget(struct dentry *dentry) |
| { |
| lockref_get(&dentry->d_lockref); |
| } |
| |
| struct dentry *dget_parent(struct dentry *dentry) |
| { |
| int gotref; |
| struct dentry *ret; |
| |
| /* |
| * Do optimistic parent lookup without any |
| * locking. |
| */ |
| rcu_read_lock(); |
| ret = ACCESS_ONCE(dentry->d_parent); |
| gotref = lockref_get_not_zero(&ret->d_lockref); |
| rcu_read_unlock(); |
| if (likely(gotref)) { |
| if (likely(ret == ACCESS_ONCE(dentry->d_parent))) |
| return ret; |
| dput(ret); |
| } |
| |
| repeat: |
| /* |
| * Don't need rcu_dereference because we re-check it was correct under |
| * the lock. |
| */ |
| rcu_read_lock(); |
| ret = dentry->d_parent; |
| spin_lock(&ret->d_lock); |
| if (unlikely(ret != dentry->d_parent)) { |
| spin_unlock(&ret->d_lock); |
| rcu_read_unlock(); |
| goto repeat; |
| } |
| rcu_read_unlock(); |
| BUG_ON(!ret->d_lockref.count); |
| ret->d_lockref.count++; |
| spin_unlock(&ret->d_lock); |
| return ret; |
| } |
| EXPORT_SYMBOL(dget_parent); |
| |
| /** |
| * d_find_alias - grab a hashed alias of inode |
| * @inode: inode in question |
| * @want_discon: flag, used by d_splice_alias, to request |
| * that only a DISCONNECTED alias be returned. |
| * |
| * If inode has a hashed alias, or is a directory and has any alias, |
| * acquire the reference to alias and return it. Otherwise return NULL. |
| * Notice that if inode is a directory there can be only one alias and |
| * it can be unhashed only if it has no children, or if it is the root |
| * of a filesystem. |
| * |
| * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer |
| * any other hashed alias over that one unless @want_discon is set, |
| * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias. |
| */ |
| static struct dentry *__d_find_alias(struct inode *inode, int want_discon) |
| { |
| struct dentry *alias, *discon_alias; |
| |
| again: |
| discon_alias = NULL; |
| hlist_for_each_entry(alias, &inode->i_dentry, d_alias) { |
| spin_lock(&alias->d_lock); |
| if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { |
| if (IS_ROOT(alias) && |
| (alias->d_flags & DCACHE_DISCONNECTED)) { |
| discon_alias = alias; |
| } else if (!want_discon) { |
| __dget_dlock(alias); |
| spin_unlock(&alias->d_lock); |
| return alias; |
| } |
| } |
| spin_unlock(&alias->d_lock); |
| } |
| if (discon_alias) { |
| alias = discon_alias; |
| spin_lock(&alias->d_lock); |
| if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { |
| if (IS_ROOT(alias) && |
| (alias->d_flags & DCACHE_DISCONNECTED)) { |
| __dget_dlock(alias); |
| spin_unlock(&alias->d_lock); |
| return alias; |
| } |
| } |
| spin_unlock(&alias->d_lock); |
| goto again; |
| } |
| return NULL; |
| } |
| |
| struct dentry *d_find_alias(struct inode *inode) |
| { |
| struct dentry *de = NULL; |
| |
| if (!hlist_empty(&inode->i_dentry)) { |
| spin_lock(&inode->i_lock); |
| de = __d_find_alias(inode, 0); |
| spin_unlock(&inode->i_lock); |
| } |
| return de; |
| } |
| EXPORT_SYMBOL(d_find_alias); |
| |
| /* |
| * Try to kill dentries associated with this inode. |
| * WARNING: you must own a reference to inode. |
| */ |
| void d_prune_aliases(struct inode *inode) |
| { |
| struct dentry *dentry; |
| restart: |
| spin_lock(&inode->i_lock); |
| hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) { |
| spin_lock(&dentry->d_lock); |
| if (!dentry->d_lockref.count) { |
| /* |
| * inform the fs via d_prune that this dentry |
| * is about to be unhashed and destroyed. |
| */ |
| if ((dentry->d_flags & DCACHE_OP_PRUNE) && |
| !d_unhashed(dentry)) |
| dentry->d_op->d_prune(dentry); |
| |
| __dget_dlock(dentry); |
| __d_drop(dentry); |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&inode->i_lock); |
| dput(dentry); |
| goto restart; |
| } |
| spin_unlock(&dentry->d_lock); |
| } |
| spin_unlock(&inode->i_lock); |
| } |
| EXPORT_SYMBOL(d_prune_aliases); |
| |
| /* |
| * Try to throw away a dentry - free the inode, dput the parent. |
| * Requires dentry->d_lock is held, and dentry->d_count == 0. |
| * Releases dentry->d_lock. |
| * |
| * This may fail if locks cannot be acquired no problem, just try again. |
| */ |
| static struct dentry * try_prune_one_dentry(struct dentry *dentry) |
| __releases(dentry->d_lock) |
| { |
| struct dentry *parent; |
| |
| parent = dentry_kill(dentry, 0); |
| /* |
| * If dentry_kill returns NULL, we have nothing more to do. |
| * if it returns the same dentry, trylocks failed. In either |
| * case, just loop again. |
| * |
| * Otherwise, we need to prune ancestors too. This is necessary |
| * to prevent quadratic behavior of shrink_dcache_parent(), but |
| * is also expected to be beneficial in reducing dentry cache |
| * fragmentation. |
| */ |
| if (!parent) |
| return NULL; |
| if (parent == dentry) |
| return dentry; |
| |
| /* Prune ancestors. */ |
| dentry = parent; |
| while (dentry) { |
| if (lockref_put_or_lock(&dentry->d_lockref)) |
| return NULL; |
| dentry = dentry_kill(dentry, 1); |
| } |
| return NULL; |
| } |
| |
| static void shrink_dentry_list(struct list_head *list) |
| { |
| struct dentry *dentry; |
| |
| rcu_read_lock(); |
| for (;;) { |
| dentry = list_entry_rcu(list->prev, struct dentry, d_lru); |
| if (&dentry->d_lru == list) |
| break; /* empty */ |
| |
| /* |
| * Get the dentry lock, and re-verify that the dentry is |
| * this on the shrinking list. If it is, we know that |
| * DCACHE_SHRINK_LIST and DCACHE_LRU_LIST are set. |
| */ |
| spin_lock(&dentry->d_lock); |
| if (dentry != list_entry(list->prev, struct dentry, d_lru)) { |
| spin_unlock(&dentry->d_lock); |
| continue; |
| } |
| |
| /* |
| * The dispose list is isolated and dentries are not accounted |
| * to the LRU here, so we can simply remove it from the list |
| * here regardless of whether it is referenced or not. |
| */ |
| d_shrink_del(dentry); |
| |
| /* |
| * We found an inuse dentry which was not removed from |
| * the LRU because of laziness during lookup. Do not free it. |
| */ |
| if (dentry->d_lockref.count) { |
| spin_unlock(&dentry->d_lock); |
| continue; |
| } |
| rcu_read_unlock(); |
| |
| /* |
| * If 'try_to_prune()' returns a dentry, it will |
| * be the same one we passed in, and d_lock will |
| * have been held the whole time, so it will not |
| * have been added to any other lists. We failed |
| * to get the inode lock. |
| * |
| * We just add it back to the shrink list. |
| */ |
| dentry = try_prune_one_dentry(dentry); |
| |
| rcu_read_lock(); |
| if (dentry) { |
| d_shrink_add(dentry, list); |
| spin_unlock(&dentry->d_lock); |
| } |
| } |
| rcu_read_unlock(); |
| } |
| |
| static enum lru_status |
| dentry_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg) |
| { |
| struct list_head *freeable = arg; |
| struct dentry *dentry = container_of(item, struct dentry, d_lru); |
| |
| |
| /* |
| * we are inverting the lru lock/dentry->d_lock here, |
| * so use a trylock. If we fail to get the lock, just skip |
| * it |
| */ |
| if (!spin_trylock(&dentry->d_lock)) |
| return LRU_SKIP; |
| |
| /* |
| * Referenced dentries are still in use. If they have active |
| * counts, just remove them from the LRU. Otherwise give them |
| * another pass through the LRU. |
| */ |
| if (dentry->d_lockref.count) { |
| d_lru_isolate(dentry); |
| spin_unlock(&dentry->d_lock); |
| return LRU_REMOVED; |
| } |
| |
| if (dentry->d_flags & DCACHE_REFERENCED) { |
| dentry->d_flags &= ~DCACHE_REFERENCED; |
| spin_unlock(&dentry->d_lock); |
| |
| /* |
| * The list move itself will be made by the common LRU code. At |
| * this point, we've dropped the dentry->d_lock but keep the |
| * lru lock. This is safe to do, since every list movement is |
| * protected by the lru lock even if both locks are held. |
| * |
| * This is guaranteed by the fact that all LRU management |
| * functions are intermediated by the LRU API calls like |
| * list_lru_add and list_lru_del. List movement in this file |
| * only ever occur through this functions or through callbacks |
| * like this one, that are called from the LRU API. |
| * |
| * The only exceptions to this are functions like |
| * shrink_dentry_list, and code that first checks for the |
| * DCACHE_SHRINK_LIST flag. Those are guaranteed to be |
| * operating only with stack provided lists after they are |
| * properly isolated from the main list. It is thus, always a |
| * local access. |
| */ |
| return LRU_ROTATE; |
| } |
| |
| d_lru_shrink_move(dentry, freeable); |
| spin_unlock(&dentry->d_lock); |
| |
| return LRU_REMOVED; |
| } |
| |
| /** |
| * prune_dcache_sb - shrink the dcache |
| * @sb: superblock |
| * @nr_to_scan : number of entries to try to free |
| * @nid: which node to scan for freeable entities |
| * |
| * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is |
| * done when we need more memory an called from the superblock shrinker |
| * function. |
| * |
| * This function may fail to free any resources if all the dentries are in |
| * use. |
| */ |
| long prune_dcache_sb(struct super_block *sb, unsigned long nr_to_scan, |
| int nid) |
| { |
| LIST_HEAD(dispose); |
| long freed; |
| |
| freed = list_lru_walk_node(&sb->s_dentry_lru, nid, dentry_lru_isolate, |
| &dispose, &nr_to_scan); |
| shrink_dentry_list(&dispose); |
| return freed; |
| } |
| |
| static enum lru_status dentry_lru_isolate_shrink(struct list_head *item, |
| spinlock_t *lru_lock, void *arg) |
| { |
| struct list_head *freeable = arg; |
| struct dentry *dentry = container_of(item, struct dentry, d_lru); |
| |
| /* |
| * we are inverting the lru lock/dentry->d_lock here, |
| * so use a trylock. If we fail to get the lock, just skip |
| * it |
| */ |
| if (!spin_trylock(&dentry->d_lock)) |
| return LRU_SKIP; |
| |
| d_lru_shrink_move(dentry, freeable); |
| spin_unlock(&dentry->d_lock); |
| |
| return LRU_REMOVED; |
| } |
| |
| |
| /** |
| * shrink_dcache_sb - shrink dcache for a superblock |
| * @sb: superblock |
| * |
| * Shrink the dcache for the specified super block. This is used to free |
| * the dcache before unmounting a file system. |
| */ |
| void shrink_dcache_sb(struct super_block *sb) |
| { |
| long freed; |
| |
| do { |
| LIST_HEAD(dispose); |
| |
| freed = list_lru_walk(&sb->s_dentry_lru, |
| dentry_lru_isolate_shrink, &dispose, UINT_MAX); |
| |
| this_cpu_sub(nr_dentry_unused, freed); |
| shrink_dentry_list(&dispose); |
| } while (freed > 0); |
| } |
| EXPORT_SYMBOL(shrink_dcache_sb); |
| |
| /** |
| * enum d_walk_ret - action to talke during tree walk |
| * @D_WALK_CONTINUE: contrinue walk |
| * @D_WALK_QUIT: quit walk |
| * @D_WALK_NORETRY: quit when retry is needed |
| * @D_WALK_SKIP: skip this dentry and its children |
| */ |
| enum d_walk_ret { |
| D_WALK_CONTINUE, |
| D_WALK_QUIT, |
| D_WALK_NORETRY, |
| D_WALK_SKIP, |
| }; |
| |
| /** |
| * d_walk - walk the dentry tree |
| * @parent: start of walk |
| * @data: data passed to @enter() and @finish() |
| * @enter: callback when first entering the dentry |
| * @finish: callback when successfully finished the walk |
| * |
| * The @enter() and @finish() callbacks are called with d_lock held. |
| */ |
| static void d_walk(struct dentry *parent, void *data, |
| enum d_walk_ret (*enter)(void *, struct dentry *), |
| void (*finish)(void *)) |
| { |
| struct dentry *this_parent; |
| struct list_head *next; |
| unsigned seq = 0; |
| enum d_walk_ret ret; |
| bool retry = true; |
| |
| again: |
| read_seqbegin_or_lock(&rename_lock, &seq); |
| this_parent = parent; |
| spin_lock(&this_parent->d_lock); |
| |
| ret = enter(data, this_parent); |
| switch (ret) { |
| case D_WALK_CONTINUE: |
| break; |
| case D_WALK_QUIT: |
| case D_WALK_SKIP: |
| goto out_unlock; |
| case D_WALK_NORETRY: |
| retry = false; |
| break; |
| } |
| repeat: |
| next = this_parent->d_subdirs.next; |
| resume: |
| while (next != &this_parent->d_subdirs) { |
| struct list_head *tmp = next; |
| struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); |
| next = tmp->next; |
| |
| spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
| |
| ret = enter(data, dentry); |
| switch (ret) { |
| case D_WALK_CONTINUE: |
| break; |
| case D_WALK_QUIT: |
| spin_unlock(&dentry->d_lock); |
| goto out_unlock; |
| case D_WALK_NORETRY: |
| retry = false; |
| break; |
| case D_WALK_SKIP: |
| spin_unlock(&dentry->d_lock); |
| continue; |
| } |
| |
| if (!list_empty(&dentry->d_subdirs)) { |
| spin_unlock(&this_parent->d_lock); |
| spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); |
| this_parent = dentry; |
| spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); |
| goto repeat; |
| } |
| spin_unlock(&dentry->d_lock); |
| } |
| /* |
| * All done at this level ... ascend and resume the search. |
| */ |
| if (this_parent != parent) { |
| struct dentry *child = this_parent; |
| this_parent = child->d_parent; |
| |
| rcu_read_lock(); |
| spin_unlock(&child->d_lock); |
| spin_lock(&this_parent->d_lock); |
| |
| /* |
| * might go back up the wrong parent if we have had a rename |
| * or deletion |
| */ |
| if (this_parent != child->d_parent || |
| (child->d_flags & DCACHE_DENTRY_KILLED) || |
| need_seqretry(&rename_lock, seq)) { |
| spin_unlock(&this_parent->d_lock); |
| rcu_read_unlock(); |
| goto rename_retry; |
| } |
| rcu_read_unlock(); |
| next = child->d_u.d_child.next; |
| goto resume; |
| } |
| if (need_seqretry(&rename_lock, seq)) { |
| spin_unlock(&this_parent->d_lock); |
| goto rename_retry; |
| } |
| if (finish) |
| finish(data); |
| |
| out_unlock: |
| spin_unlock(&this_parent->d_lock); |
| done_seqretry(&rename_lock, seq); |
| return; |
| |
| rename_retry: |
| if (!retry) |
| return; |
| seq = 1; |
| goto again; |
| } |
| |
| /* |
| * Search for at least 1 mount point in the dentry's subdirs. |
| * We descend to the next level whenever the d_subdirs |
| * list is non-empty and continue searching. |
| */ |
| |
| static enum d_walk_ret check_mount(void *data, struct dentry *dentry) |
| { |
| int *ret = data; |
| if (d_mountpoint(dentry)) { |
| *ret = 1; |
| return D_WALK_QUIT; |
| } |
| return D_WALK_CONTINUE; |
| } |
| |
| /** |
| * have_submounts - check for mounts over a dentry |
| * @parent: dentry to check. |
| * |
| * Return true if the parent or its subdirectories contain |
| * a mount point |
| */ |
| int have_submounts(struct dentry *parent) |
| { |
| int ret = 0; |
| |
| d_walk(parent, &ret, check_mount, NULL); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(have_submounts); |
| |
| /* |
| * Called by mount code to set a mountpoint and check if the mountpoint is |
| * reachable (e.g. NFS can unhash a directory dentry and then the complete |
| * subtree can become unreachable). |
| * |
| * Only one of check_submounts_and_drop() and d_set_mounted() must succeed. For |
| * this reason take rename_lock and d_lock on dentry and ancestors. |
| */ |
| int d_set_mounted(struct dentry *dentry) |
| { |
| struct dentry *p; |
| int ret = -ENOENT; |
| write_seqlock(&rename_lock); |
| for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) { |
| /* Need exclusion wrt. check_submounts_and_drop() */ |
| spin_lock(&p->d_lock); |
| if (unlikely(d_unhashed(p))) { |
| spin_unlock(&p->d_lock); |
| goto out; |
| } |
| spin_unlock(&p->d_lock); |
| } |
| spin_lock(&dentry->d_lock); |
| if (!d_unlinked(dentry)) { |
| dentry->d_flags |= DCACHE_MOUNTED; |
| ret = 0; |
| } |
| spin_unlock(&dentry->d_lock); |
| out: |
| write_sequnlock(&rename_lock); |
| return ret; |
| } |
| |
| /* |
| * Search the dentry child list of the specified parent, |
| * and move any unused dentries to the end of the unused |
| * list for prune_dcache(). We descend to the next level |
| * whenever the d_subdirs list is non-empty and continue |
| * searching. |
| * |
| * It returns zero iff there are no unused children, |
| * otherwise it returns the number of children moved to |
| * the end of the unused list. This may not be the total |
| * number of unused children, because select_parent can |
| * drop the lock and return early due to latency |
| * constraints. |
| */ |
| |
| struct select_data { |
| struct dentry *start; |
| struct list_head dispose; |
| int found; |
| }; |
| |
| static enum d_walk_ret select_collect(void *_data, struct dentry *dentry) |
| { |
| struct select_data *data = _data; |
| enum d_walk_ret ret = D_WALK_CONTINUE; |
| |
| if (data->start == dentry) |
| goto out; |
| |
| /* |
| * move only zero ref count dentries to the dispose list. |
| * |
| * Those which are presently on the shrink list, being processed |
| * by shrink_dentry_list(), shouldn't be moved. Otherwise the |
| * loop in shrink_dcache_parent() might not make any progress |
| * and loop forever. |
| */ |
| if (dentry->d_lockref.count) { |
| dentry_lru_del(dentry); |
| } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) { |
| /* |
| * We can't use d_lru_shrink_move() because we |
| * need to get the global LRU lock and do the |
| * LRU accounting. |
| */ |
| d_lru_del(dentry); |
| d_shrink_add(dentry, &data->dispose); |
| data->found++; |
| ret = D_WALK_NORETRY; |
| } |
| /* |
| * We can return to the caller if we have found some (this |
| * ensures forward progress). We'll be coming back to find |
| * the rest. |
| */ |
| if (data->found && need_resched()) |
| ret = D_WALK_QUIT; |
| out: |
| return ret; |
| } |
| |
| /** |
| * shrink_dcache_parent - prune dcache |
| * @parent: parent of entries to prune |
| * |
| * Prune the dcache to remove unused children of the parent dentry. |
| */ |
| void shrink_dcache_parent(struct dentry *parent) |
| { |
| for (;;) { |
| struct select_data data; |
| |
| INIT_LIST_HEAD(&data.dispose); |
| data.start = parent; |
| data.found = 0; |
| |
| d_walk(parent, &data, select_collect, NULL); |
| if (!data.found) |
| break; |
| |
| shrink_dentry_list(&data.dispose); |
| cond_resched(); |
| } |
| } |
| EXPORT_SYMBOL(shrink_dcache_parent); |
| |
| static enum d_walk_ret umount_collect(void *_data, struct dentry *dentry) |
| { |
| struct select_data *data = _data; |
| enum d_walk_ret ret = D_WALK_CONTINUE; |
| |
| if (dentry->d_lockref.count) { |
| dentry_lru_del(dentry); |
| if (likely(!list_empty(&dentry->d_subdirs))) |
| goto out; |
| if (dentry == data->start && dentry->d_lockref.count == 1) |
| goto out; |
| printk(KERN_ERR |
| "BUG: Dentry %p{i=%lx,n=%s}" |
| " still in use (%d)" |
| " [unmount of %s %s]\n", |
| dentry, |
| dentry->d_inode ? |
| dentry->d_inode->i_ino : 0UL, |
| dentry->d_name.name, |
| dentry->d_lockref.count, |
| dentry->d_sb->s_type->name, |
| dentry->d_sb->s_id); |
| BUG(); |
| } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) { |
| /* |
| * We can't use d_lru_shrink_move() because we |
| * need to get the global LRU lock and do the |
| * LRU accounting. |
| */ |
| if (dentry->d_flags & DCACHE_LRU_LIST) |
| d_lru_del(dentry); |
| d_shrink_add(dentry, &data->dispose); |
| data->found++; |
| ret = D_WALK_NORETRY; |
| } |
| out: |
| if (data->found && need_resched()) |
| ret = D_WALK_QUIT; |
| return ret; |
| } |
| |
| /* |
| * destroy the dentries attached to a superblock on unmounting |
| */ |
| void shrink_dcache_for_umount(struct super_block *sb) |
| { |
| struct dentry *dentry; |
| |
| if (down_read_trylock(&sb->s_umount)) |
| BUG(); |
| |
| dentry = sb->s_root; |
| sb->s_root = NULL; |
| for (;;) { |
| struct select_data data; |
| |
| INIT_LIST_HEAD(&data.dispose); |
| data.start = dentry; |
| data.found = 0; |
| |
| d_walk(dentry, &data, umount_collect, NULL); |
| if (!data.found) |
| break; |
| |
| shrink_dentry_list(&data.dispose); |
| cond_resched(); |
| } |
| d_drop(dentry); |
| dput(dentry); |
| |
| while (!hlist_bl_empty(&sb->s_anon)) { |
| struct select_data data; |
| dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash); |
| |
| INIT_LIST_HEAD(&data.dispose); |
| data.start = NULL; |
| data.found = 0; |
| |
| d_walk(dentry, &data, umount_collect, NULL); |
| if (data.found) |
| shrink_dentry_list(&data.dispose); |
| cond_resched(); |
| } |
| } |
| |
| static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry) |
| { |
| struct select_data *data = _data; |
| |
| if (d_mountpoint(dentry)) { |
| data->found = -EBUSY; |
| return D_WALK_QUIT; |
| } |
| |
| return select_collect(_data, dentry); |
| } |
| |
| static void check_and_drop(void *_data) |
| { |
| struct select_data *data = _data; |
| |
| if (d_mountpoint(data->start)) |
| data->found = -EBUSY; |
| if (!data->found) |
| __d_drop(data->start); |
| } |
| |
| /** |
| * check_submounts_and_drop - prune dcache, check for submounts and drop |
| * |
| * All done as a single atomic operation relative to has_unlinked_ancestor(). |
| * Returns 0 if successfully unhashed @parent. If there were submounts then |
| * return -EBUSY. |
| * |
| * @dentry: dentry to prune and drop |
| */ |
| int check_submounts_and_drop(struct dentry *dentry) |
| { |
| int ret = 0; |
| |
| /* Negative dentries can be dropped without further checks */ |
| if (!dentry->d_inode) { |
| d_drop(dentry); |
| goto out; |
| } |
| |
| for (;;) { |
| struct select_data data; |
| |
| INIT_LIST_HEAD(&data.dispose); |
| data.start = dentry; |
| data.found = 0; |
| |
| d_walk(dentry, &data, check_and_collect, check_and_drop); |
| ret = data.found; |
| |
| if (!list_empty(&data.dispose)) |
| shrink_dentry_list(&data.dispose); |
| |
| if (ret <= 0) |
| break; |
| |
| cond_resched(); |
| } |
| |
| out: |
| return ret; |
| } |
| EXPORT_SYMBOL(check_submounts_and_drop); |
| |
| /** |
| * __d_alloc - allocate a dcache entry |
| * @sb: filesystem it will belong to |
| * @name: qstr of the name |
| * |
| * Allocates a dentry. It returns %NULL if there is insufficient memory |
| * available. On a success the dentry is returned. The name passed in is |
| * copied and the copy passed in may be reused after this call. |
| */ |
| |
| struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) |
| { |
| struct dentry *dentry; |
| char *dname; |
| |
| dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); |
| if (!dentry) |
| return NULL; |
| |
| /* |
| * We guarantee that the inline name is always NUL-terminated. |
| * This way the memcpy() done by the name switching in rename |
| * will still always have a NUL at the end, even if we might |
| * be overwriting an internal NUL character |
| */ |
| dentry->d_iname[DNAME_INLINE_LEN-1] = 0; |
| if (name->len > DNAME_INLINE_LEN-1) { |
| dname = kmalloc(name->len + 1, GFP_KERNEL); |
| if (!dname) { |
| kmem_cache_free(dentry_cache, dentry); |
| return NULL; |
| } |
| } else { |
| dname = dentry->d_iname; |
| } |
| |
| dentry->d_name.len = name->len; |
| dentry->d_name.hash = name->hash; |
| memcpy(dname, name->name, name->len); |
| dname[name->len] = 0; |
| |
| /* Make sure we always see the terminating NUL character */ |
| smp_wmb(); |
| dentry->d_name.name = dname; |
| |
| dentry->d_lockref.count = 1; |
| dentry->d_flags = 0; |
| spin_lock_init(&dentry->d_lock); |
| seqcount_init(&dentry->d_seq); |
| dentry->d_inode = NULL; |
| dentry->d_parent = dentry; |
| dentry->d_sb = sb; |
| dentry->d_op = NULL; |
| dentry->d_fsdata = NULL; |
| INIT_HLIST_BL_NODE(&dentry->d_hash); |
| INIT_LIST_HEAD(&dentry->d_lru); |
| INIT_LIST_HEAD(&dentry->d_subdirs); |
| INIT_HLIST_NODE(&dentry->d_alias); |
| INIT_LIST_HEAD(&dentry->d_u.d_child); |
| d_set_d_op(dentry, dentry->d_sb->s_d_op); |
| |
| this_cpu_inc(nr_dentry); |
| |
| return dentry; |
| } |
| |
| /** |
| * d_alloc - allocate a dcache entry |
| * @parent: parent of entry to allocate |
| * @name: qstr of the name |
| * |
| * Allocates a dentry. It returns %NULL if there is insufficient memory |
| * available. On a success the dentry is returned. The name passed in is |
| * copied and the copy passed in may be reused after this call. |
| */ |
| struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) |
| { |
| struct dentry *dentry = __d_alloc(parent->d_sb, name); |
| if (!dentry) |
| return NULL; |
| |
| spin_lock(&parent->d_lock); |
| /* |
| * don't need child lock because it is not subject |
| * to concurrency here |
| */ |
| __dget_dlock(parent); |
| dentry->d_parent = parent; |
| list_add(&dentry->d_u.d_child, &parent->d_subdirs); |
| spin_unlock(&parent->d_lock); |
| |
| return dentry; |
| } |
| EXPORT_SYMBOL(d_alloc); |
| |
| /** |
| * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems) |
| * @sb: the superblock |
| * @name: qstr of the name |
| * |
| * For a filesystem that just pins its dentries in memory and never |
| * performs lookups at all, return an unhashed IS_ROOT dentry. |
| */ |
| struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name) |
| { |
| return __d_alloc(sb, name); |
| } |
| EXPORT_SYMBOL(d_alloc_pseudo); |
| |
| struct dentry *d_alloc_name(struct dentry *parent, const char *name) |
| { |
| struct qstr q; |
| |
| q.name = name; |
| q.len = strlen(name); |
| q.hash = full_name_hash(q.name, q.len); |
| return d_alloc(parent, &q); |
| } |
| EXPORT_SYMBOL(d_alloc_name); |
| |
| void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) |
| { |
| WARN_ON_ONCE(dentry->d_op); |
| WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH | |
| DCACHE_OP_COMPARE | |
| DCACHE_OP_REVALIDATE | |
| DCACHE_OP_WEAK_REVALIDATE | |
| DCACHE_OP_DELETE )); |
| dentry->d_op = op; |
| if (!op) |
| return; |
| if (op->d_hash) |
| dentry->d_flags |= DCACHE_OP_HASH; |
| if (op->d_compare) |
| dentry->d_flags |= DCACHE_OP_COMPARE; |
| if (op->d_revalidate) |
| dentry->d_flags |= DCACHE_OP_REVALIDATE; |
| if (op->d_weak_revalidate) |
| dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE; |
| if (op->d_delete) |
| dentry->d_flags |= DCACHE_OP_DELETE; |
| if (op->d_prune) |
| dentry->d_flags |= DCACHE_OP_PRUNE; |
| |
| } |
| EXPORT_SYMBOL(d_set_d_op); |
| |
| static unsigned d_flags_for_inode(struct inode *inode) |
| { |
| unsigned add_flags = DCACHE_FILE_TYPE; |
| |
| if (!inode) |
| return DCACHE_MISS_TYPE; |
| |
| if (S_ISDIR(inode->i_mode)) { |
| add_flags = DCACHE_DIRECTORY_TYPE; |
| if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) { |
| if (unlikely(!inode->i_op->lookup)) |
| add_flags = DCACHE_AUTODIR_TYPE; |
| else |
| inode->i_opflags |= IOP_LOOKUP; |
| } |
| } else if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) { |
| if (unlikely(inode->i_op->follow_link)) |
| add_flags = DCACHE_SYMLINK_TYPE; |
| else |
| inode->i_opflags |= IOP_NOFOLLOW; |
| } |
| |
| if (unlikely(IS_AUTOMOUNT(inode))) |
| add_flags |= DCACHE_NEED_AUTOMOUNT; |
| return add_flags; |
| } |
| |
| static void __d_instantiate(struct dentry *dentry, struct inode *inode) |
| { |
| unsigned add_flags = d_flags_for_inode(inode); |
| |
| spin_lock(&dentry->d_lock); |
| dentry->d_flags &= ~DCACHE_ENTRY_TYPE; |
| dentry->d_flags |= add_flags; |
| if (inode) |
| hlist_add_head(&dentry->d_alias, &inode->i_dentry); |
| dentry->d_inode = inode; |
| dentry_rcuwalk_barrier(dentry); |
| spin_unlock(&dentry->d_lock); |
| fsnotify_d_instantiate(dentry, inode); |
| } |
| |
| /** |
| * d_instantiate - fill in inode information for a dentry |
| * @entry: dentry to complete |
| * @inode: inode to attach to this dentry |
| * |
| * Fill in inode information in the entry. |
| * |
| * This turns negative dentries into productive full members |
| * of society. |
| * |
| * NOTE! This assumes that the inode count has been incremented |
| * (or otherwise set) by the caller to indicate that it is now |
| * in use by the dcache. |
| */ |
| |
| void d_instantiate(struct dentry *entry, struct inode * inode) |
| { |
| BUG_ON(!hlist_unhashed(&entry->d_alias)); |
| if (inode) |
| spin_lock(&inode->i_lock); |
| __d_instantiate(entry, inode); |
| if (inode) |
| spin_unlock(&inode->i_lock); |
| security_d_instantiate(entry, inode); |
| } |
| EXPORT_SYMBOL(d_instantiate); |
| |
| /** |
| * d_instantiate_unique - instantiate a non-aliased dentry |
| * @entry: dentry to instantiate |
| * @inode: inode to attach to this dentry |
| * |
| * Fill in inode information in the entry. On success, it returns NULL. |
| * If an unhashed alias of "entry" already exists, then we return the |
| * aliased dentry instead and drop one reference to inode. |
| * |
| * Note that in order to avoid conflicts with rename() etc, the caller |
| * had better be holding the parent directory semaphore. |
| * |
| * This also assumes that the inode count has been incremented |
| * (or otherwise set) by the caller to indicate that it is now |
| * in use by the dcache. |
| */ |
| static struct dentry *__d_instantiate_unique(struct dentry *entry, |
| struct inode *inode) |
| { |
| struct dentry *alias; |
| int len = entry->d_name.len; |
| const char *name = entry->d_name.name; |
| unsigned int hash = entry->d_name.hash; |
| |
| if (!inode) { |
| __d_instantiate(entry, NULL); |
| return NULL; |
| } |
| |
| hlist_for_each_entry(alias, &inode->i_dentry, d_alias) { |
| /* |
| * Don't need alias->d_lock here, because aliases with |
| * d_parent == entry->d_parent are not subject to name or |
| * parent changes, because the parent inode i_mutex is held. |
| */ |
| if (alias->d_name.hash != hash) |
| continue; |
| if (alias->d_parent != entry->d_parent) |
| continue; |
| if (alias->d_name.len != len) |
| continue; |
| if (dentry_cmp(alias, name, len)) |
| continue; |
| __dget(alias); |
| return alias; |
| } |
| |
| __d_instantiate(entry, inode); |
| return NULL; |
| } |
| |
| struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode) |
| { |
| struct dentry *result; |
| |
| BUG_ON(!hlist_unhashed(&entry->d_alias)); |
| |
| if (inode) |
| spin_lock(&inode->i_lock); |
| result = __d_instantiate_unique(entry, inode); |
| if (inode) |
| spin_unlock(&inode->i_lock); |
| |
| if (!result) { |
| security_d_instantiate(entry, inode); |
| return NULL; |
| } |
| |
| BUG_ON(!d_unhashed(result)); |
| iput(inode); |
| return result; |
| } |
| |
| EXPORT_SYMBOL(d_instantiate_unique); |
| |
| /** |
| * d_instantiate_no_diralias - instantiate a non-aliased dentry |
| * @entry: dentry to complete |
| * @inode: inode to attach to this dentry |
| * |
| * Fill in inode information in the entry. If a directory alias is found, then |
| * return an error (and drop inode). Together with d_materialise_unique() this |
| * guarantees that a directory inode may never have more than one alias. |
| */ |
| int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode) |
| { |
| BUG_ON(!hlist_unhashed(&entry->d_alias)); |
| |
| spin_lock(&inode->i_lock); |
| if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) { |
| spin_unlock(&inode->i_lock); |
| iput(inode); |
| return -EBUSY; |
| } |
| __d_instantiate(entry, inode); |
| spin_unlock(&inode->i_lock); |
| security_d_instantiate(entry, inode); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(d_instantiate_no_diralias); |
| |
| struct dentry *d_make_root(struct inode *root_inode) |
| { |
| struct dentry *res = NULL; |
| |
| if (root_inode) { |
| static const struct qstr name = QSTR_INIT("/", 1); |
| |
| res = __d_alloc(root_inode->i_sb, &name); |
| if (res) |
| d_instantiate(res, root_inode); |
| else |
| iput(root_inode); |
| } |
| return res; |
| } |
| EXPORT_SYMBOL(d_make_root); |
| |
| static struct dentry * __d_find_any_alias(struct inode *inode) |
| { |
| struct dentry *alias; |
| |
| if (hlist_empty(&inode->i_dentry)) |
| return NULL; |
| alias = hlist_entry(inode->i_dentry.first, struct dentry, d_alias); |
| __dget(alias); |
| return alias; |
| } |
| |
| /** |
| * d_find_any_alias - find any alias for a given inode |
| * @inode: inode to find an alias for |
| * |
| * If any aliases exist for the given inode, take and return a |
| * reference for one of them. If no aliases exist, return %NULL. |
| */ |
| struct dentry *d_find_any_alias(struct inode *inode) |
| { |
| struct dentry *de; |
| |
| spin_lock(&inode->i_lock); |
| de = __d_find_any_alias(inode); |
| spin_unlock(&inode->i_lock); |
| return de; |
| } |
| EXPORT_SYMBOL(d_find_any_alias); |
| |
| /** |
| * d_obtain_alias - find or allocate a dentry for a given inode |
| * @inode: inode to allocate the dentry for |
| * |
| * Obtain a dentry for an inode resulting from NFS filehandle conversion or |
| * similar open by handle operations. The returned dentry may be anonymous, |
| * or may have a full name (if the inode was already in the cache). |
| * |
| * When called on a directory inode, we must ensure that the inode only ever |
| * has one dentry. If a dentry is found, that is returned instead of |
| * allocating a new one. |
| * |
| * On successful return, the reference to the inode has been transferred |
| * to the dentry. In case of an error the reference on the inode is released. |
| * To make it easier to use in export operations a %NULL or IS_ERR inode may |
| * be passed in and will be the error will be propagate to the return value, |
| * with a %NULL @inode replaced by ERR_PTR(-ESTALE). |
| */ |
| struct dentry *d_obtain_alias(struct inode *inode) |
| { |
| static const struct qstr anonstring = QSTR_INIT("/", 1); |
| struct dentry *tmp; |
| struct dentry *res; |
| unsigned add_flags; |
| |
| if (!inode) |
| return ERR_PTR(-ESTALE); |
| if (IS_ERR(inode)) |
| return ERR_CAST(inode); |
| |
| res = d_find_any_alias(inode); |
| if (res) |
| goto out_iput; |
| |
| tmp = __d_alloc(inode->i_sb, &anonstring); |
| if (!tmp) { |
| res = ERR_PTR(-ENOMEM); |
| goto out_iput; |
| } |
| |
| spin_lock(&inode->i_lock); |
| res = __d_find_any_alias(inode); |
| if (res) { |
| spin_unlock(&inode->i_lock); |
| dput(tmp); |
| goto out_iput; |
| } |
| |
| /* attach a disconnected dentry */ |
| add_flags = d_flags_for_inode(inode) | DCACHE_DISCONNECTED; |
| |
| spin_lock(&tmp->d_lock); |
| tmp->d_inode = inode; |
| tmp->d_flags |= add_flags; |
| hlist_add_head(&tmp->d_alias, &inode->i_dentry); |
| hlist_bl_lock(&tmp->d_sb->s_anon); |
| hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon); |
| hlist_bl_unlock(&tmp->d_sb->s_anon); |
| spin_unlock(&tmp->d_lock); |
| spin_unlock(&inode->i_lock); |
| security_d_instantiate(tmp, inode); |
| |
| return tmp; |
| |
| out_iput: |
| if (res && !IS_ERR(res)) |
| security_d_instantiate(res, inode); |
| iput(inode); |
| return res; |
| } |
| EXPORT_SYMBOL(d_obtain_alias); |
| |
| /** |
| * d_splice_alias - splice a disconnected dentry into the tree if one exists |
| * @inode: the inode which may have a disconnected dentry |
| * @dentry: a negative dentry which we want to point to the inode. |
| * |
| * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and |
| * DCACHE_DISCONNECTED), then d_move that in place of the given dentry |
| * and return it, else simply d_add the inode to the dentry and return NULL. |
| * |
| * This is needed in the lookup routine of any filesystem that is exportable |
| * (via knfsd) so that we can build dcache paths to directories effectively. |
| * |
| * If a dentry was found and moved, then it is returned. Otherwise NULL |
| * is returned. This matches the expected return value of ->lookup. |
| * |
| * Cluster filesystems may call this function with a negative, hashed dentry. |
| * In that case, we know that the inode will be a regular file, and also this |
| * will only occur during atomic_open. So we need to check for the dentry |
| * being already hashed only in the final case. |
| */ |
| struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) |
| { |
| struct dentry *new = NULL; |
| |
| if (IS_ERR(inode)) |
| return ERR_CAST(inode); |
| |
| if (inode && S_ISDIR(inode->i_mode)) { |
| spin_lock(&inode->i_lock); |
| new = __d_find_alias(inode, 1); |
| if (new) { |
| BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); |
| spin_unlock(&inode->i_lock); |
| security_d_instantiate(new, inode); |
| d_move(new, dentry); |
| iput(inode); |
| } else { |
| /* already taking inode->i_lock, so d_add() by hand */ |
| __d_instantiate(dentry, inode); |
| spin_unlock(&inode->i_lock); |
| security_d_instantiate(dentry, inode); |
| d_rehash(dentry); |
| } |
| } else { |
| d_instantiate(dentry, inode); |
| if (d_unhashed(dentry)) |
| d_rehash(dentry); |
| } |
| return new; |
| } |
| EXPORT_SYMBOL(d_splice_alias); |
| |
| /** |
| * d_add_ci - lookup or allocate new dentry with case-exact name |
| * @inode: the inode case-insensitive lookup has found |
| * @dentry: the negative dentry that was passed to the parent's lookup func |
| * @name: the case-exact name to be associated with the returned dentry |
| * |
| * This is to avoid filling the dcache with case-insensitive names to the |
| * same inode, only the actual correct case is stored in the dcache for |
| * case-insensitive filesystems. |
| * |
| * For a case-insensitive lookup match and if the the case-exact dentry |
| * already exists in in the dcache, use it and return it. |
| * |
| * If no entry exists with the exact case name, allocate new dentry with |
| * the exact case, and return the spliced entry. |
| */ |
| struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, |
| struct qstr *name) |
| { |
| struct dentry *found; |
| struct dentry *new; |
| |
| /* |
| * First check if a dentry matching the name already exists, |
| * if not go ahead and create it now. |
| */ |
| found = d_hash_and_lookup(dentry->d_parent, name); |
| if (unlikely(IS_ERR(found))) |
| goto err_out; |
| if (!found) { |
| new = d_alloc(dentry->d_parent, name); |
| if (!new) { |
| found = ERR_PTR(-ENOMEM); |
| goto err_out; |
| } |
| |
| found = d_splice_alias(inode, new); |
| if (found) { |
| dput(new); |
| return found; |
| } |
| return new; |
| } |
| |
| /* |
| * If a matching dentry exists, and it's not negative use it. |
| * |
| * Decrement the reference count to balance the iget() done |
| * earlier on. |
| */ |
| if (found->d_inode) { |
| if (unlikely(found->d_inode != inode)) { |
| /* This can't happen because bad inodes are unhashed. */ |
| BUG_ON(!is_bad_inode(inode)); |
| BUG_ON(!is_bad_inode(found->d_inode)); |
| } |
| iput(inode); |
| return found; |
| } |
| |
| /* |
| * Negative dentry: instantiate it unless the inode is a directory and |
| * already has a dentry. |
| */ |
| new = d_splice_alias(inode, found); |
| if (new) { |
| dput(found); |
| found = new; |
| } |
| return found; |
| |
| err_out: |
| iput(inode); |
| return found; |
| } |
| EXPORT_SYMBOL(d_add_ci); |
| |
| /* |
| * Do the slow-case of the dentry name compare. |
| * |
| * Unlike the dentry_cmp() function, we need to atomically |
| * load the name and length information, so that the |
| * filesystem can rely on them, and can use the 'name' and |
| * 'len' information without worrying about walking off the |
| * end of memory etc. |
| * |
| * Thus the read_seqcount_retry() and the "duplicate" info |
| * in arguments (the low-level filesystem should not look |
| * at the dentry inode or name contents directly, since |
| * rename can change them while we're in RCU mode). |
| */ |
| enum slow_d_compare { |
| D_COMP_OK, |
| D_COMP_NOMATCH, |
| D_COMP_SEQRETRY, |
| }; |
| |
| static noinline enum slow_d_compare slow_dentry_cmp( |
| const struct dentry *parent, |
| struct dentry *dentry, |
| unsigned int seq, |
| const struct qstr *name) |
| { |
| int tlen = dentry->d_name.len; |
| const char *tname = dentry->d_name.name; |
| |
| if (read_seqcount_retry(&dentry->d_seq, seq)) { |
| cpu_relax(); |
| return D_COMP_SEQRETRY; |
| } |
| if (parent->d_op->d_compare(parent, dentry, tlen, tname, name)) |
| return D_COMP_NOMATCH; |
| return D_COMP_OK; |
| } |
| |
| /** |
| * __d_lookup_rcu - search for a dentry (racy, store-free) |
| * @parent: parent dentry |
| * @name: qstr of name we wish to find |
| * @seqp: returns d_seq value at the point where the dentry was found |
| * Returns: dentry, or NULL |
| * |
| * __d_lookup_rcu is the dcache lookup function for rcu-walk name |
| * resolution (store-free path walking) design described in |
| * Documentation/filesystems/path-lookup.txt. |
| * |
| * This is not to be used outside core vfs. |
| * |
| * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock |
| * held, and rcu_read_lock held. The returned dentry must not be stored into |
| * without taking d_lock and checking d_seq sequence count against @seq |
| * returned here. |
| * |
| * A refcount may be taken on the found dentry with the d_rcu_to_refcount |
| * function. |
| * |
| * Alternatively, __d_lookup_rcu may be called again to look up the child of |
| * the returned dentry, so long as its parent's seqlock is checked after the |
| * child is looked up. Thus, an interlocking stepping of sequence lock checks |
| * is formed, giving integrity down the path walk. |
| * |
| * NOTE! The caller *has* to check the resulting dentry against the sequence |
| * number we've returned before using any of the resulting dentry state! |
| */ |
| struct dentry *__d_lookup_rcu(const struct dentry *parent, |
| const struct qstr *name, |
| unsigned *seqp) |
| { |
| u64 hashlen = name->hash_len; |
| const unsigned char *str = name->name; |
| struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen)); |
| struct hlist_bl_node *node; |
| struct dentry *dentry; |
| |
| /* |
| * Note: There is significant duplication with __d_lookup_rcu which is |
| * required to prevent single threaded performance regressions |
| * especially on architectures where smp_rmb (in seqcounts) are costly. |
| * Keep the two functions in sync. |
| */ |
| |
| /* |
| * The hash list is protected using RCU. |
| * |
| * Carefully use d_seq when comparing a candidate dentry, to avoid |
| * races with d_move(). |
| * |
| * It is possible that concurrent renames can mess up our list |
| * walk here and result in missing our dentry, resulting in the |
| * false-negative result. d_lookup() protects against concurrent |
| * renames using rename_lock seqlock. |
| * |
| * See Documentation/filesystems/path-lookup.txt for more details. |
| */ |
| hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
| unsigned seq; |
| |
| seqretry: |
| /* |
| * The dentry sequence count protects us from concurrent |
| * renames, and thus protects parent and name fields. |
| * |
| * The caller must perform a seqcount check in order |
| * to do anything useful with the returned dentry. |
| * |
| * NOTE! We do a "raw" seqcount_begin here. That means that |
| * we don't wait for the sequence count to stabilize if it |
| * is in the middle of a sequence change. If we do the slow |
| * dentry compare, we will do seqretries until it is stable, |
| * and if we end up with a successful lookup, we actually |
| * want to exit RCU lookup anyway. |
| */ |
| seq = raw_seqcount_begin(&dentry->d_seq); |
| if (dentry->d_parent != parent) |
| continue; |
| if (d_unhashed(dentry)) |
| continue; |
| |
| if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { |
| if (dentry->d_name.hash != hashlen_hash(hashlen)) |
| continue; |
| *seqp = seq; |
| switch (slow_dentry_cmp(parent, dentry, seq, name)) { |
| case D_COMP_OK: |
| return dentry; |
| case D_COMP_NOMATCH: |
| continue; |
| default: |
| goto seqretry; |
| } |
| } |
| |
| if (dentry->d_name.hash_len != hashlen) |
| continue; |
| *seqp = seq; |
| if (!dentry_cmp(dentry, str, hashlen_len(hashlen))) |
| return dentry; |
| } |
| return NULL; |
| } |
| |
| /** |
| * d_lookup - search for a dentry |
| * @parent: parent dentry |
| * @name: qstr of name we wish to find |
| * Returns: dentry, or NULL |
| * |
| * d_lookup searches the children of the parent dentry for the name in |
| * question. If the dentry is found its reference count is incremented and the |
| * dentry is returned. The caller must use dput to free the entry when it has |
| * finished using it. %NULL is returned if the dentry does not exist. |
| */ |
| struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name) |
| { |
| struct dentry *dentry; |
| unsigned seq; |
| |
| do { |
| seq = read_seqbegin(&rename_lock); |
| dentry = __d_lookup(parent, name); |
| if (dentry) |
| break; |
| } while (read_seqretry(&rename_lock, seq)); |
| return dentry; |
| } |
| EXPORT_SYMBOL(d_lookup); |
| |
| /** |
| * __d_lookup - search for a dentry (racy) |
| * @parent: parent dentry |
| * @name: qstr of name we wish to find |
| * Returns: dentry, or NULL |
| * |
| * __d_lookup is like d_lookup, however it may (rarely) return a |
| * false-negative result due to unrelated rename activity. |
| * |
| * __d_lookup is slightly faster by avoiding rename_lock read seqlock, |
| * however it must be used carefully, eg. with a following d_lookup in |
| * the case of failure. |
| * |
| * __d_lookup callers must be commented. |
| */ |
| struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name) |
| { |
| unsigned int len = name->len; |
| unsigned int hash = name->hash; |
| const unsigned char *str = name->name; |
| struct hlist_bl_head *b = d_hash(parent, hash); |
| struct hlist_bl_node *node; |
| struct dentry *found = NULL; |
| struct dentry *dentry; |
| |
| /* |
| * Note: There is significant duplication with __d_lookup_rcu which is |
| * required to prevent single threaded performance regressions |
| * especially on architectures where smp_rmb (in seqcounts) are costly. |
| * Keep the two functions in sync. |
| */ |
| |
| /* |
| * The hash list is protected using RCU. |
| * |
| * Take d_lock when comparing a candidate dentry, to avoid races |
| * with d_move(). |
| * |
| * It is possible that concurrent renames can mess up our list |
| * walk here and result in missing our dentry, resulting in the |
| * false-negative result. d_lookup() protects against concurrent |
| * renames using rename_lock seqlock. |
| * |
| * See Documentation/filesystems/path-lookup.txt for more details. |
| */ |
| rcu_read_lock(); |
| |
| hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
| |
| if (dentry->d_name.hash != hash) |
| continue; |
| |
| spin_lock(&dentry->d_lock); |
| if (dentry->d_parent != parent) |
| goto next; |
| if (d_unhashed(dentry)) |
| goto next; |
| |
| /* |
| * It is safe to compare names since d_move() cannot |
| * change the qstr (protected by d_lock). |
| */ |
| if (parent->d_flags & DCACHE_OP_COMPARE) { |
| int tlen = dentry->d_name.len; |
| const char *tname = dentry->d_name.name; |
| if (parent->d_op->d_compare(parent, dentry, tlen, tname, name)) |
| goto next; |
| } else { |
| if (dentry->d_name.len != len) |
| goto next; |
| if (dentry_cmp(dentry, str, len)) |
| goto next; |
| } |
| |
| dentry->d_lockref.count++; |
| found = dentry; |
| spin_unlock(&dentry->d_lock); |
| break; |
| next: |
| spin_unlock(&dentry->d_lock); |
| } |
| rcu_read_unlock(); |
| |
| return found; |
| } |
| |
| /** |
| * d_hash_and_lookup - hash the qstr then search for a dentry |
| * @dir: Directory to search in |
| * @name: qstr of name we wish to find |
| * |
| * On lookup failure NULL is returned; on bad name - ERR_PTR(-error) |
| */ |
| struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) |
| { |
| /* |
| * Check for a fs-specific hash function. Note that we must |
| * calculate the standard hash first, as the d_op->d_hash() |
| * routine may choose to leave the hash value unchanged. |
| */ |
| name->hash = full_name_hash(name->name, name->len); |
| if (dir->d_flags & DCACHE_OP_HASH) { |
| int err = dir->d_op->d_hash(dir, name); |
| if (unlikely(err < 0)) |
| return ERR_PTR(err); |
| } |
| return d_lookup(dir, name); |
| } |
| EXPORT_SYMBOL(d_hash_and_lookup); |
| |
| /** |
| * d_validate - verify dentry provided from insecure source (deprecated) |
| * @dentry: The dentry alleged to be valid child of @dparent |
| * @dparent: The parent dentry (known to be valid) |
| * |
| * An insecure source has sent us a dentry, here we verify it and dget() it. |
| * This is used by ncpfs in its readdir implementation. |
| * Zero is returned in the dentry is invalid. |
| * |
| * This function is slow for big directories, and deprecated, do not use it. |
| */ |
| int d_validate(struct dentry *dentry, struct dentry *dparent) |
| { |
| struct dentry *child; |
| |
| spin_lock(&dparent->d_lock); |
| list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) { |
| if (dentry == child) { |
| spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
| __dget_dlock(dentry); |
| spin_unlock(&dentry->d_lock); |
| spin_unlock(&dparent->d_lock); |
| return 1; |
| } |
| } |
| spin_unlock(&dparent->d_lock); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(d_validate); |
| |
| /* |
| * When a file is deleted, we have two options: |
| * - turn this dentry into a negative dentry |
| * - unhash this dentry and free it. |
| * |
| * Usually, we want to just turn this into |
| * a negative dentry, but if anybody else is |
| * currently using the dentry or the inode |
| * we can't do that and we fall back on removing |
| * it from the hash queues and waiting for |
| * it to be deleted later when it has no users |
| */ |
| |
| /** |
| * d_delete - delete a dentry |
| * @dentry: The dentry to delete |
| * |
| * Turn the dentry into a negative dentry if possible, otherwise |
| * remove it from the hash queues so it can be deleted later |
| */ |
| |
| void d_delete(struct dentry * dentry) |
| { |
| struct inode *inode; |
| int isdir = 0; |
| /* |
| * Are we the only user? |
| */ |
| again: |
| spin_lock(&dentry->d_lock); |
| inode = dentry->d_inode; |
| isdir = S_ISDIR(inode->i_mode); |
| if (dentry->d_lockref.count == 1) { |
| if (!spin_trylock(&inode->i_lock)) { |
| spin_unlock(&dentry->d_lock); |
| cpu_relax(); |
| goto again; |
| } |
| dentry->d_flags &= ~DCACHE_CANT_MOUNT; |
| dentry_unlink_inode(dentry); |
| fsnotify_nameremove(dentry, isdir); |
| return; |
| } |
| |
| if (!d_unhashed(dentry)) |
| __d_drop(dentry); |
| |
| spin_unlock(&dentry->d_lock); |
| |
| fsnotify_nameremove(dentry, isdir); |
| } |
| EXPORT_SYMBOL(d_delete); |
| |
| static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b) |
| { |
| BUG_ON(!d_unhashed(entry)); |
| hlist_bl_lock(b); |
| entry->d_flags |= DCACHE_RCUACCESS; |
| hlist_bl_add_head_rcu(&entry->d_hash, b); |
| hlist_bl_unlock(b); |
| } |
| |
| static void _d_rehash(struct dentry * entry) |
| { |
| __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash)); |
| } |
| |
| /** |
| * d_rehash - add an entry back to the hash |
| * @entry: dentry to add to the hash |
| * |
| * Adds a dentry to the hash according to its name. |
| */ |
| |
| void d_rehash(struct dentry * entry) |
| { |
| spin_lock(&entry->d_lock); |
| _d_rehash(entry); |
| spin_unlock(&entry->d_lock); |
| } |
| EXPORT_SYMBOL(d_rehash); |
| |
| /** |
| * dentry_update_name_case - update case insensitive dentry with a new name |
| * @dentry: dentry to be updated |
| * @name: new name |
| * |
| * Update a case insensitive dentry with new case of name. |
| * |
| * dentry must have been returned by d_lookup with name @name. Old and new |
| * name lengths must match (ie. no d_compare which allows mismatched name |
| * lengths). |
| * |
| * Parent inode i_mutex must be held over d_lookup and into this call (to |
| * keep renames and concurrent inserts, and readdir(2) away). |
| */ |
| void dentry_update_name_case(struct dentry *dentry, struct qstr *name) |
| { |
| BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex)); |
| BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */ |
| |
| spin_lock(&dentry->d_lock); |
| write_seqcount_begin(&dentry->d_seq); |
| memcpy((unsigned char *)dentry->d_name.name, name->name, name->len); |
| write_seqcount_end(&dentry->d_seq); |
| spin_unlock(&dentry->d_lock); |
| } |
| EXPORT_SYMBOL(dentry_update_name_case); |
| |
| static void switch_names(struct dentry *dentry, struct dentry *target) |
| { |
| if (dname_external(target)) { |
| if (dname_external(dentry)) { |
| /* |
| * Both external: swap the pointers |
| */ |
| swap(target->d_name.name, dentry->d_name.name); |
| } else { |
| /* |
| * dentry:internal, target:external. Steal target's |
| * storage and make target internal. |
| */ |
| memcpy(target->d_iname, dentry->d_name.name, |
| dentry->d_name.len + 1); |
| dentry->d_name.name = target->d_name.name; |
| target->d_name.name = target->d_iname; |
| } |
| } else { |
| if (dname_external(dentry)) { |
| /* |
| * dentry:external, target:internal. Give dentry's |
| * storage to target and make dentry internal |
| */ |
| memcpy(dentry->d_iname, target->d_name.name, |
| target->d_name.len + 1); |
| target->d_name.name = dentry->d_name.name; |
| dentry->d_name.name = dentry->d_iname; |
| } else { |
| /* |
| * Both are internal. Just copy target to dentry |
| */ |
| memcpy(dentry->d_iname, target->d_name.name, |
| target->d_name.len + 1); |
| dentry->d_name.len = target->d_name.len; |
| return; |
| } |
| } |
| swap(dentry->d_name.len, target->d_name.len); |
| } |
| |
| static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target) |
| { |
| /* |
| * XXXX: do we really need to take target->d_lock? |
| */ |
| if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent) |
| spin_lock(&target->d_parent->d_lock); |
| else { |
| if (d_ancestor(dentry->d_parent, target->d_parent)) { |
| spin_lock(&dentry->d_parent->d_lock); |
| spin_lock_nested(&target->d_parent->d_lock, |
| DENTRY_D_LOCK_NESTED); |
| } else { |
| spin_lock(&target->d_parent->d_lock); |
| spin_lock_nested(&dentry->d_parent->d_lock, |
| DENTRY_D_LOCK_NESTED); |
| } |
| } |
| if (target < dentry) { |
| spin_lock_nested(&target->d_lock, 2); |
| spin_lock_nested(&dentry->d_lock, 3); |
| } else { |
| spin_lock_nested(&dentry->d_lock, 2); |
| spin_lock_nested(&target->d_lock, 3); |
| } |
| } |
| |
| static void dentry_unlock_parents_for_move(struct dentry *dentry, |
| struct dentry *target) |
| { |
| if (target->d_parent != dentry->d_parent) |
| spin_unlock(&dentry->d_parent->d_lock); |
| if (target->d_parent != target) |
| spin_unlock(&target->d_parent->d_lock); |
| } |
| |
| /* |
| * When switching names, the actual string doesn't strictly have to |
| * be preserved in the target - because we're dropping the target |
| * anyway. As such, we can just do a simple memcpy() to copy over |
| * the new name before we switch. |
| * |
| * Note that we have to be a lot more careful about getting the hash |
| * switched - we have to switch the hash value properly even if it |
| * then no longer matches the actual (corrupted) string of the target. |
| * The hash value has to match the hash queue that the dentry is on.. |
| */ |
| /* |
| * __d_move - move a dentry |
| * @dentry: entry to move |
| * @target: new dentry |
| * |
| * Update the dcache to reflect the move of a file name. Negative |
| * dcache entries should not be moved in this way. Caller must hold |
| * rename_lock, the i_mutex of the source and target directories, |
| * and the sb->s_vfs_rename_mutex if they differ. See lock_rename(). |
| */ |
| static void __d_move(struct dentry * dentry, struct dentry * target) |
| { |
| if (!dentry->d_inode) |
| printk(KERN_WARNING "VFS: moving negative dcache entry\n"); |
| |
| BUG_ON(d_ancestor(dentry, target)); |
| BUG_ON(d_ancestor(target, dentry)); |
| |
| dentry_lock_for_move(dentry, target); |
| |
| write_seqcount_begin(&dentry->d_seq); |
| write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED); |
| |
| /* __d_drop does write_seqcount_barrier, but they're OK to nest. */ |
| |
| /* |
| * Move the dentry to the target hash queue. Don't bother checking |
| * for the same hash queue because of how unlikely it is. |
| */ |
| __d_drop(dentry); |
| __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash)); |
| |
| /* Unhash the target: dput() will then get rid of it */ |
| __d_drop(target); |
| |
| list_del(&dentry->d_u.d_child); |
| list_del(&target->d_u.d_child); |
| |
| /* Switch the names.. */ |
| switch_names(dentry, target); |
| swap(dentry->d_name.hash, target->d_name.hash); |
| |
| /* ... and switch the parents */ |
| if (IS_ROOT(dentry)) { |
| dentry->d_parent = target->d_parent; |
| target->d_parent = target; |
| INIT_LIST_HEAD(&target->d_u.d_child); |
| } else { |
| swap(dentry->d_parent, target->d_parent); |
| |
| /* And add them back to the (new) parent lists */ |
| list_add(&target->d_u.d_child, &target->d_parent->d_subdirs); |
| } |
| |
| list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); |
| |
| write_seqcount_end(&target->d_seq); |
| write_seqcount_end(&dentry->d_seq); |
| |
| dentry_unlock_parents_for_move(dentry, target); |
| spin_unlock(&target->d_lock); |
| fsnotify_d_move(dentry); |
| spin_unlock(&dentry->d_lock); |
| } |
| |
| /* |
| * d_move - move a dentry |
| * @dentry: entry to move |
| * @target: new dentry |
| * |
| * Update the dcache to reflect the move of a file name. Negative |
| * dcache entries should not be moved in this way. See the locking |
| * requirements for __d_move. |
| */ |
| void d_move(struct dentry *dentry, struct dentry *target) |
| { |
| write_seqlock(&rename_lock); |
| __d_move(dentry, target); |
| write_sequnlock(&rename_lock); |
| } |
| EXPORT_SYMBOL(d_move); |
| |
| /** |
| * d_ancestor - search for an ancestor |
| * @p1: ancestor dentry |
| * @p2: child dentry |
| * |
| * Returns the ancestor dentry of p2 which is a child of p1, if p1 is |
| * an ancestor of p2, else NULL. |
| */ |
| struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) |
| { |
| struct dentry *p; |
| |
| for (p = p2; !IS_ROOT(p); p = p->d_parent) { |
| if (p->d_parent == p1) |
| return p; |
| } |
| return NULL; |
| } |
| |
| /* |
| * This helper attempts to cope with remotely renamed directories |
| * |
| * It assumes that the caller is already holding |
| * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock |
| * |
| * Note: If ever the locking in lock_rename() changes, then please |
| * remember to update this too... |
| */ |
| static struct dentry *__d_unalias(struct inode *inode, |
| struct dentry *dentry, struct dentry *alias) |
| { |
| struct mutex *m1 = NULL, *m2 = NULL; |
| struct dentry *ret = ERR_PTR(-EBUSY); |
| |
| /* If alias and dentry share a parent, then no extra locks required */ |
| if (alias->d_parent == dentry->d_parent) |
| goto out_unalias; |
| |
| /* See lock_rename() */ |
| if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) |
| goto out_err; |
| m1 = &dentry->d_sb->s_vfs_rename_mutex; |
| if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex)) |
| goto out_err; |
| m2 = &alias->d_parent->d_inode->i_mutex; |
| out_unalias: |
| if (likely(!d_mountpoint(alias))) { |
| __d_move(alias, dentry); |
| ret = alias; |
| } |
| out_err: |
| spin_unlock(&inode->i_lock); |
| if (m2) |
| mutex_unlock(m2); |
| if (m1) |
| mutex_unlock(m1); |
| return ret; |
| } |
| |
| /* |
| * Prepare an anonymous dentry for life in the superblock's dentry tree as a |
| * named dentry in place of the dentry to be replaced. |
| * returns with anon->d_lock held! |
| */ |
| static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) |
| { |
| struct dentry *dparent; |
| |
| dentry_lock_for_move(anon, dentry); |
| |
| write_seqcount_begin(&dentry->d_seq); |
| write_seqcount_begin_nested(&anon->d_seq, DENTRY_D_LOCK_NESTED); |
| |
| dparent = dentry->d_parent; |
| |
| switch_names(dentry, anon); |
| swap(dentry->d_name.hash, anon->d_name.hash); |
| |
| dentry->d_parent = dentry; |
| list_del_init(&dentry->d_u.d_child); |
| anon->d_parent = dparent; |
| list_move(&anon->d_u.d_child, &dparent->d_subdirs); |
| |
| write_seqcount_end(&dentry->d_seq); |
| write_seqcount_end(&anon->d_seq); |
| |
| dentry_unlock_parents_for_move(anon, dentry); |
| spin_unlock(&dentry->d_lock); |
| |
| /* anon->d_lock still locked, returns locked */ |
| } |
| |
| /** |
| * d_materialise_unique - introduce an inode into the tree |
| * @dentry: candidate dentry |
| * @inode: inode to bind to the dentry, to which aliases may be attached |
| * |
| * Introduces an dentry into the tree, substituting an extant disconnected |
| * root directory alias in its place if there is one. Caller must hold the |
| * i_mutex of the parent directory. |
| */ |
| struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) |
| { |
| struct dentry *actual; |
| |
| BUG_ON(!d_unhashed(dentry)); |
| |
| if (!inode) { |
| actual = dentry; |
| __d_instantiate(dentry, NULL); |
| d_rehash(actual); |
| goto out_nolock; |
| } |
| |
| spin_lock(&inode->i_lock); |
| |
| if (S_ISDIR(inode->i_mode)) { |
| struct dentry *alias; |
| |
| /* Does an aliased dentry already exist? */ |
| alias = __d_find_alias(inode, 0); |
| if (alias) { |
| actual = alias; |
| write_seqlock(&rename_lock); |
| |
| if (d_ancestor(alias, dentry)) { |
| /* Check for loops */ |
| actual = ERR_PTR(-ELOOP); |
| spin_unlock(&inode->i_lock); |
| } else if (IS_ROOT(alias)) { |
| /* Is this an anonymous mountpoint that we |
| * could splice into our tree? */ |
| __d_materialise_dentry(dentry, alias); |
| write_sequnlock(&rename_lock); |
| __d_drop(alias); |
| goto found; |
| } else { |
| /* Nope, but we must(!) avoid directory |
| * aliasing. This drops inode->i_lock */ |
| actual = __d_unalias(inode, dentry, alias); |
| } |
| write_sequnlock(&rename_lock); |
| if (IS_ERR(actual)) { |
| if (PTR_ERR(actual) == -ELOOP) |
| pr_warn_ratelimited( |
| "VFS: Lookup of '%s' in %s %s" |
| " would have caused loop\n", |
| dentry->d_name.name, |
| inode->i_sb->s_type->name, |
| inode->i_sb->s_id); |
| dput(alias); |
| } |
| goto out_nolock; |
| } |
| } |
| |
| /* Add a unique reference */ |
| actual = __d_instantiate_unique(dentry, inode); |
| if (!actual) |
| actual = dentry; |
| else |
| BUG_ON(!d_unhashed(actual)); |
| |
| spin_lock(&actual->d_lock); |
| found: |
| _d_rehash(actual); |
| spin_unlock(&actual->d_lock); |
| spin_unlock(&inode->i_lock); |
| out_nolock: |
| if (actual == dentry) { |
| security_d_instantiate(dentry, inode); |
| return NULL; |
| } |
| |
| iput(inode); |
| return actual; |
| } |
| EXPORT_SYMBOL_GPL(d_materialise_unique); |
| |
| static int prepend(char **buffer, int *buflen, const char *str, int namelen) |
| { |
| *buflen -= namelen; |
| if (*buflen < 0) |
| return -ENAMETOOLONG; |
| *buffer -= namelen; |
| memcpy(*buffer, str, namelen); |
| return 0; |
| } |
| |
| /** |
| * prepend_name - prepend a pathname in front of current buffer pointer |
| * @buffer: buffer pointer |
| * @buflen: allocated length of the buffer |
| * @name: name string and length qstr structure |
| * |
| * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to |
| * make sure that either the old or the new name pointer and length are |
| * fetched. However, there may be mismatch between length and pointer. |
| * The length cannot be trusted, we need to copy it byte-by-byte until |
| * the length is reached or a null byte is found. It also prepends "/" at |
| * the beginning of the name. The sequence number check at the caller will |
| * retry it again when a d_move() does happen. So any garbage in the buffer |
| * due to mismatched pointer and length will be discarded. |
| */ |
| static int prepend_name(char **buffer, int *buflen, struct qstr *name) |
| { |
| const char *dname = ACCESS_ONCE(name->name); |
| u32 dlen = ACCESS_ONCE(name->len); |
| char *p; |
| |
| *buflen -= dlen + 1; |
| if (*buflen < 0) |
| return -ENAMETOOLONG; |
| p = *buffer -= dlen + 1; |
| *p++ = '/'; |
| while (dlen--) { |
| char c = *dname++; |
| if (!c) |
| break; |
| *p++ = c; |
| } |
| return 0; |
| } |
| |
| /** |
| * prepend_path - Prepend path string to a buffer |
| * @path: the dentry/vfsmount to report |
| * @root: root vfsmnt/dentry |
| * @buffer: pointer to the end of the buffer |
| * @buflen: pointer to buffer length |
| * |
| * The function will first try to write out the pathname without taking any |
| * lock other than the RCU read lock to make sure that dentries won't go away. |
| * It only checks the sequence number of the global rename_lock as any change |
| * in the dentry's d_seq will be preceded by changes in the rename_lock |
| * sequence number. If the sequence number had been changed, it will restart |
| * the whole pathname back-tracing sequence again by taking the rename_lock. |
| * In this case, there is no need to take the RCU read lock as the recursive |
| * parent pointer references will keep the dentry chain alive as long as no |
| * rename operation is performed. |
| */ |
| static int prepend_path(const struct path *path, |
| const struct path *root, |
| char **buffer, int *buflen) |
| { |
| struct dentry *dentry; |
| struct vfsmount *vfsmnt; |
| struct mount *mnt; |
| int error = 0; |
| unsigned seq, m_seq = 0; |
| char *bptr; |
| int blen; |
| |
| rcu_read_lock(); |
| restart_mnt: |
| read_seqbegin_or_lock(&mount_lock, &m_seq); |
| seq = 0; |
| rcu_read_lock(); |
| restart: |
| bptr = *buffer; |
| blen = *buflen; |
| error = 0; |
| dentry = path->dentry; |
| vfsmnt = path->mnt; |
| mnt = real_mount(vfsmnt); |
| read_seqbegin_or_lock(&rename_lock, &seq); |
| while (dentry != root->dentry || vfsmnt != root->mnt) { |
| struct dentry * parent; |
| |
| if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { |
| struct mount *parent = ACCESS_ONCE(mnt->mnt_parent); |
| /* Global root? */ |
| if (mnt != parent) { |
| dentry = ACCESS_ONCE(mnt->mnt_mountpoint); |
| mnt = parent; |
| vfsmnt = &mnt->mnt; |
| continue; |
| } |
| /* |
| * Filesystems needing to implement special "root names" |
| * should do so with ->d_dname() |
| */ |
| if (IS_ROOT(dentry) && |
| (dentry->d_name.len != 1 || |
| dentry->d_name.name[0] != '/')) { |
| WARN(1, "Root dentry has weird name <%.*s>\n", |
| (int) dentry->d_name.len, |
| dentry->d_name.name); |
| } |
| if (!error) |
| error = is_mounted(vfsmnt) ? 1 : 2; |
| break; |
| } |
| parent = dentry->d_parent; |
| prefetch(parent); |
| error = prepend_name(&bptr, &blen, &dentry->d_name); |
| if (error) |
| break; |
| |
| dentry = parent; |
| } |
| if (!(seq & 1)) |
| rcu_read_unlock(); |
| if (need_seqretry(&rename_lock, seq)) { |
| seq = 1; |
| goto restart; |
| } |
| done_seqretry(&rename_lock, seq); |
| |
| if (!(m_seq & 1)) |
| rcu_read_unlock(); |
| if (need_seqretry(&mount_lock, m_seq)) { |
| m_seq = 1; |
| goto restart_mnt; |
| } |
| done_seqretry(&mount_lock, m_seq); |
| |
| if (error >= 0 && bptr == *buffer) { |
| if (--blen < 0) |
| error = -ENAMETOOLONG; |
| else |
| *--bptr = '/'; |
| } |
| *buffer = bptr; |
| *buflen = blen; |
| return error; |
| } |
| |
| /** |
| * __d_path - return the path of a dentry |
| * @path: the dentry/vfsmount to report |
| * @root: root vfsmnt/dentry |
| * @buf: buffer to return value in |
| * @buflen: buffer length |
| * |
| * Convert a dentry into an ASCII path name. |
| * |
| * Returns a pointer into the buffer or an error code if the |
| * path was too long. |
| * |
| * "buflen" should be positive. |
| * |
| * If the path is not reachable from the supplied root, return %NULL. |
| */ |
| char *__d_path(const struct path *path, |
| const struct path *root, |
| char *buf, int buflen) |
| { |
| char *res = buf + buflen; |
| int error; |
| |
| prepend(&res, &buflen, "\0", 1); |
| error = prepend_path(path, root, &res, &buflen); |
| |
| if (error < 0) |
| return ERR_PTR(error); |
| if (error > 0) |
| return NULL; |
| return res; |
| } |
| |
| char *d_absolute_path(const struct path *path, |
| char *buf, int buflen) |
| { |
| struct path root = {}; |
| char *res = buf + buflen; |
| int error; |
| |
| prepend(&res, &buflen, "\0", 1); |
| error = prepend_path(path, &root, &res, &buflen); |
| |
| if (error > 1) |
| error = -EINVAL; |
| if (error < 0) |
| return ERR_PTR(error); |
| return res; |
| } |
| |
| /* |
| * same as __d_path but appends "(deleted)" for unlinked files. |
| */ |
| static int path_with_deleted(const struct path *path, |
| const struct path *root, |
| char **buf, int *buflen) |
| { |
| prepend(buf, buflen, "\0", 1); |
| if (d_unlinked(path->dentry)) { |
| int error = prepend(buf, buflen, " (deleted)", 10); |
| if (error) |
| return error; |
| } |
| |
| return prepend_path(path, root, buf, buflen); |
| } |
| |
| static int prepend_unreachable(char **buffer, int *buflen) |
| { |
| return prepend(buffer, buflen, "(unreachable)", 13); |
| } |
| |
| static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) |
| { |
| unsigned seq; |
| |
| do { |
| seq = read_seqcount_begin(&fs->seq); |
| *root = fs->root; |
| } while (read_seqcount_retry(&fs->seq, seq)); |
| } |
| |
| /** |
| * d_path - return the path of a dentry |
| * @path: path to report |
| * @buf: buffer to return value in |
| * @buflen: buffer length |
| * |
| * Convert a dentry into an ASCII path name. If the entry has been deleted |
| * the string " (deleted)" is appended. Note that this is ambiguous. |
| * |
| * Returns a pointer into the buffer or an error code if the path was |
| * too long. Note: Callers should use the returned pointer, not the passed |
| * in buffer, to use the name! The implementation often starts at an offset |
| * into the buffer, and may leave 0 bytes at the start. |
| * |
| * "buflen" should be positive. |
| */ |
| char *d_path(const struct path *path, char *buf, int buflen) |
| { |
| char *res = buf + buflen; |
| struct path root; |
| int error; |
| |
| /* |
| * We have various synthetic filesystems that never get mounted. On |
| * these filesystems dentries are never used for lookup purposes, and |
| * thus don't need to be hashed. They also don't need a name until a |
| * user wants to identify the object in /proc/pid/fd/. The little hack |
| * below allows us to generate a name for these objects on demand: |
| * |
| * Some pseudo inodes are mountable. When they are mounted |
| * path->dentry == path->mnt->mnt_root. In that case don't call d_dname |
| * and instead have d_path return the mounted path. |
| */ |
| if (path->dentry->d_op && path->dentry->d_op->d_dname && |
| (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root)) |
| return path->dentry->d_op->d_dname(path->dentry, buf, buflen); |
| |
| rcu_read_lock(); |
| get_fs_root_rcu(current->fs, &root); |
| error = path_with_deleted(path, &root, &res, &buflen); |
| rcu_read_unlock(); |
| |
| if (error < 0) |
| res = ERR_PTR(error); |
| return res; |
| } |
| EXPORT_SYMBOL(d_path); |
| |
| /* |
| * Helper function for dentry_operations.d_dname() members |
| */ |
| char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, |
| const char *fmt, ...) |
| { |
| va_list args; |
| char temp[64]; |
| int sz; |
| |
| va_start(args, fmt); |
| sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; |
| va_end(args); |
| |
| if (sz > sizeof(temp) || sz > buflen) |
| return ERR_PTR(-ENAMETOOLONG); |
| |
| buffer += buflen - sz; |
| return memcpy(buffer, temp, sz); |
| } |
| |
| char *simple_dname(struct dentry *dentry, char *buffer, int buflen) |
| { |
| char *end = buffer + buflen; |
| /* these dentries are never renamed, so d_lock is not needed */ |
| if (prepend(&end, &buflen, " (deleted)", 11) || |
| prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) || |
| prepend(&end, &buflen, "/", 1)) |
| end = ERR_PTR(-ENAMETOOLONG); |
| return end; |
| } |
| |
| /* |
| * Write full pathname from the root of the filesystem into the buffer. |
| */ |
| static char *__dentry_path(struct dentry *d, char *buf, int buflen) |
| { |
| struct dentry *dentry; |
| char *end, *retval; |
| int len, seq = 0; |
| int error = 0; |
| |
| if (buflen < 2) |
| goto Elong; |
| |
| rcu_read_lock(); |
| restart: |
| dentry = d; |
| end = buf + buflen; |
| len = buflen; |
| prepend(&end, &len, "\0", 1); |
| /* Get '/' right */ |
| retval = end-1; |
| *retval = '/'; |
| read_seqbegin_or_lock(&rename_lock, &seq); |
| while (!IS_ROOT(dentry)) { |
| struct dentry *parent = dentry->d_parent; |
| |
| prefetch(parent); |
| error = prepend_name(&end, &len, &dentry->d_name); |
| if (error) |
| break; |
| |
| retval = end; |
| dentry = parent; |
| } |
| if (!(seq & 1)) |
| rcu_read_unlock(); |
| if (need_seqretry(&rename_lock, seq)) { |
| seq = 1; |
| goto restart; |
| } |
| done_seqretry(&rename_lock, seq); |
| if (error) |
| goto Elong; |
| return retval; |
| Elong: |
| return ERR_PTR(-ENAMETOOLONG); |
| } |
| |
| char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen) |
| { |
| return __dentry_path(dentry, buf, buflen); |
| } |
| EXPORT_SYMBOL(dentry_path_raw); |
| |
| char *dentry_path(struct dentry *dentry, char *buf, int buflen) |
| { |
| char *p = NULL; |
| char *retval; |
| |
| if (d_unlinked(dentry)) { |
| p = buf + buflen; |
| if (prepend(&p, &buflen, "//deleted", 10) != 0) |
| goto Elong; |
| buflen++; |
| } |
| retval = __dentry_path(dentry, buf, buflen); |
| if (!IS_ERR(retval) && p) |
| *p = '/'; /* restore '/' overriden with '\0' */ |
| return retval; |
| Elong: |
| return ERR_PTR(-ENAMETOOLONG); |
| } |
| |
| static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, |
| struct path *pwd) |
| { |
| unsigned seq; |
| |
| do { |
| seq = read_seqcount_begin(&fs->seq); |
| *root = fs->root; |
| *pwd = fs->pwd; |
| } while (read_seqcount_retry(&fs->seq, seq)); |
| } |
| |
| /* |
| * NOTE! The user-level library version returns a |
| * character pointer. The kernel system call just |
| * returns the length of the buffer filled (which |
| * includes the ending '\0' character), or a negative |
| * error value. So libc would do something like |
| * |
| * char *getcwd(char * buf, size_t size) |
| * { |
| * int retval; |
| * |
| * retval = sys_getcwd(buf, size); |
| * if (retval >= 0) |
| * return buf; |
| * errno = -retval; |
| * return NULL; |
| * } |
| */ |
| SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) |
| { |
| int error; |
| struct path pwd, root; |
| char *page = __getname(); |
| |
| if (!page) |
| return -ENOMEM; |
| |
| rcu_read_lock(); |
| get_fs_root_and_pwd_rcu(current->fs, &root, &pwd); |
| |
| error = -ENOENT; |
| if (!d_unlinked(pwd.dentry)) { |
| unsigned long len; |
| char *cwd = page + PATH_MAX; |
| int buflen = PATH_MAX; |
| |
| prepend(&cwd, &buflen, "\0", 1); |
| error = prepend_path(&pwd, &root, &cwd, &buflen); |
| rcu_read_unlock(); |
| |
| if (error < 0) |
| goto out; |
| |
| /* Unreachable from current root */ |
| if (error > 0) { |
| error = prepend_unreachable(&cwd, &buflen); |
| if (error) |
| goto out; |
| } |
| |
| error = -ERANGE; |
| len = PATH_MAX + page - cwd; |
| if (len <= size) { |
| error = len; |
| if (copy_to_user(buf, cwd, len)) |
| error = -EFAULT; |
| } |
| } else { |
| rcu_read_unlock(); |
| } |
| |
| out: |
| __putname(page); |
| return error; |
| } |
| |
| /* |
| * Test whether new_dentry is a subdirectory of old_dentry. |
| * |
| * Trivially implemented using the dcache structure |
| */ |
| |
| /** |
| * is_subdir - is new dentry a subdirectory of old_dentry |
| * @new_dentry: new dentry |
| * @old_dentry: old dentry |
| * |
| * Returns 1 if new_dentry is a subdirectory of the parent (at any depth). |
| * Returns 0 otherwise. |
| * Caller must ensure that "new_dentry" is pinned before calling is_subdir() |
| */ |
| |
| int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) |
| { |
| int result; |
| unsigned seq; |
| |
| if (new_dentry == old_dentry) |
| return 1; |
| |
| do { |
| /* for restarting inner loop in case of seq retry */ |
| seq = read_seqbegin(&rename_lock); |
| /* |
| * Need rcu_readlock to protect against the d_parent trashing |
| * due to d_move |
| */ |
| rcu_read_lock(); |
| if (d_ancestor(old_dentry, new_dentry)) |
| result = 1; |
| else |
| result = 0; |
| rcu_read_unlock(); |
| } while (read_seqretry(&rename_lock, seq)); |
| |
| return result; |
| } |
| |
| static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry) |
| { |
| struct dentry *root = data; |
| if (dentry != root) { |
| if (d_unhashed(dentry) || !dentry->d_inode) |
| return D_WALK_SKIP; |
| |
| if (!(dentry->d_flags & DCACHE_GENOCIDE)) { |
| dentry->d_flags |= DCACHE_GENOCIDE; |
| dentry->d_lockref.count--; |
| } |
| } |
| return D_WALK_CONTINUE; |
| } |
| |
| void d_genocide(struct dentry *parent) |
| { |
| d_walk(parent, parent, d_genocide_kill, NULL); |
| } |
|