| /* |
| * linux/fs/file_table.c |
| * |
| * Copyright (C) 1991, 1992 Linus Torvalds |
| * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu) |
| */ |
| |
| #include <linux/string.h> |
| #include <linux/slab.h> |
| #include <linux/file.h> |
| #include <linux/fdtable.h> |
| #include <linux/init.h> |
| #include <linux/module.h> |
| #include <linux/fs.h> |
| #include <linux/security.h> |
| #include <linux/cred.h> |
| #include <linux/eventpoll.h> |
| #include <linux/rcupdate.h> |
| #include <linux/mount.h> |
| #include <linux/capability.h> |
| #include <linux/cdev.h> |
| #include <linux/fsnotify.h> |
| #include <linux/sysctl.h> |
| #include <linux/percpu_counter.h> |
| #include <linux/percpu.h> |
| #include <linux/hardirq.h> |
| #include <linux/task_work.h> |
| #include <linux/ima.h> |
| #include <linux/swap.h> |
| |
| #include <linux/atomic.h> |
| |
| #include "internal.h" |
| |
| /* sysctl tunables... */ |
| struct files_stat_struct files_stat = { |
| .max_files = NR_FILE |
| }; |
| |
| /* SLAB cache for file structures */ |
| static struct kmem_cache *filp_cachep __read_mostly; |
| |
| static struct percpu_counter nr_files __cacheline_aligned_in_smp; |
| |
| static void file_free_rcu(struct rcu_head *head) |
| { |
| struct file *f = container_of(head, struct file, f_u.fu_rcuhead); |
| |
| put_cred(f->f_cred); |
| kmem_cache_free(filp_cachep, f); |
| } |
| |
| static inline void file_free(struct file *f) |
| { |
| percpu_counter_dec(&nr_files); |
| call_rcu(&f->f_u.fu_rcuhead, file_free_rcu); |
| } |
| |
| /* |
| * Return the total number of open files in the system |
| */ |
| static long get_nr_files(void) |
| { |
| return percpu_counter_read_positive(&nr_files); |
| } |
| |
| /* |
| * Return the maximum number of open files in the system |
| */ |
| unsigned long get_max_files(void) |
| { |
| return files_stat.max_files; |
| } |
| EXPORT_SYMBOL_GPL(get_max_files); |
| |
| /* |
| * Handle nr_files sysctl |
| */ |
| #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) |
| int proc_nr_files(struct ctl_table *table, int write, |
| void __user *buffer, size_t *lenp, loff_t *ppos) |
| { |
| files_stat.nr_files = get_nr_files(); |
| return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| } |
| #else |
| int proc_nr_files(struct ctl_table *table, int write, |
| void __user *buffer, size_t *lenp, loff_t *ppos) |
| { |
| return -ENOSYS; |
| } |
| #endif |
| |
| /* Find an unused file structure and return a pointer to it. |
| * Returns an error pointer if some error happend e.g. we over file |
| * structures limit, run out of memory or operation is not permitted. |
| * |
| * Be very careful using this. You are responsible for |
| * getting write access to any mount that you might assign |
| * to this filp, if it is opened for write. If this is not |
| * done, you will imbalance int the mount's writer count |
| * and a warning at __fput() time. |
| */ |
| struct file *get_empty_filp(void) |
| { |
| const struct cred *cred = current_cred(); |
| static long old_max; |
| struct file *f; |
| int error; |
| |
| /* |
| * Privileged users can go above max_files |
| */ |
| if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) { |
| /* |
| * percpu_counters are inaccurate. Do an expensive check before |
| * we go and fail. |
| */ |
| if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files) |
| goto over; |
| } |
| |
| f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL); |
| if (unlikely(!f)) |
| return ERR_PTR(-ENOMEM); |
| |
| percpu_counter_inc(&nr_files); |
| f->f_cred = get_cred(cred); |
| error = security_file_alloc(f); |
| if (unlikely(error)) { |
| file_free(f); |
| return ERR_PTR(error); |
| } |
| |
| atomic_long_set(&f->f_count, 1); |
| rwlock_init(&f->f_owner.lock); |
| spin_lock_init(&f->f_lock); |
| mutex_init(&f->f_pos_lock); |
| eventpoll_init_file(f); |
| /* f->f_version: 0 */ |
| return f; |
| |
| over: |
| /* Ran out of filps - report that */ |
| if (get_nr_files() > old_max) { |
| pr_info("VFS: file-max limit %lu reached\n", get_max_files()); |
| old_max = get_nr_files(); |
| } |
| return ERR_PTR(-ENFILE); |
| } |
| |
| /** |
| * alloc_file - allocate and initialize a 'struct file' |
| * |
| * @path: the (dentry, vfsmount) pair for the new file |
| * @mode: the mode with which the new file will be opened |
| * @fop: the 'struct file_operations' for the new file |
| */ |
| struct file *alloc_file(const struct path *path, fmode_t mode, |
| const struct file_operations *fop) |
| { |
| struct file *file; |
| |
| file = get_empty_filp(); |
| if (IS_ERR(file)) |
| return file; |
| |
| file->f_path = *path; |
| file->f_inode = path->dentry->d_inode; |
| file->f_mapping = path->dentry->d_inode->i_mapping; |
| file->f_wb_err = filemap_sample_wb_err(file->f_mapping); |
| if ((mode & FMODE_READ) && |
| likely(fop->read || fop->read_iter)) |
| mode |= FMODE_CAN_READ; |
| if ((mode & FMODE_WRITE) && |
| likely(fop->write || fop->write_iter)) |
| mode |= FMODE_CAN_WRITE; |
| file->f_mode = mode; |
| file->f_op = fop; |
| if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) |
| i_readcount_inc(path->dentry->d_inode); |
| return file; |
| } |
| EXPORT_SYMBOL(alloc_file); |
| |
| /* the real guts of fput() - releasing the last reference to file |
| */ |
| static void __fput(struct file *file) |
| { |
| struct dentry *dentry = file->f_path.dentry; |
| struct vfsmount *mnt = file->f_path.mnt; |
| struct inode *inode = file->f_inode; |
| |
| might_sleep(); |
| |
| fsnotify_close(file); |
| /* |
| * The function eventpoll_release() should be the first called |
| * in the file cleanup chain. |
| */ |
| eventpoll_release(file); |
| locks_remove_file(file); |
| |
| if (unlikely(file->f_flags & FASYNC)) { |
| if (file->f_op->fasync) |
| file->f_op->fasync(-1, file, 0); |
| } |
| ima_file_free(file); |
| if (file->f_op->release) |
| file->f_op->release(inode, file); |
| security_file_free(file); |
| if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL && |
| !(file->f_mode & FMODE_PATH))) { |
| cdev_put(inode->i_cdev); |
| } |
| fops_put(file->f_op); |
| put_pid(file->f_owner.pid); |
| if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) |
| i_readcount_dec(inode); |
| if (file->f_mode & FMODE_WRITER) { |
| put_write_access(inode); |
| __mnt_drop_write(mnt); |
| } |
| file->f_path.dentry = NULL; |
| file->f_path.mnt = NULL; |
| file->f_inode = NULL; |
| file_free(file); |
| dput(dentry); |
| mntput(mnt); |
| } |
| |
| static LLIST_HEAD(delayed_fput_list); |
| static void delayed_fput(struct work_struct *unused) |
| { |
| struct llist_node *node = llist_del_all(&delayed_fput_list); |
| struct file *f, *t; |
| |
| llist_for_each_entry_safe(f, t, node, f_u.fu_llist) |
| __fput(f); |
| } |
| |
| static void ____fput(struct callback_head *work) |
| { |
| __fput(container_of(work, struct file, f_u.fu_rcuhead)); |
| } |
| |
| /* |
| * If kernel thread really needs to have the final fput() it has done |
| * to complete, call this. The only user right now is the boot - we |
| * *do* need to make sure our writes to binaries on initramfs has |
| * not left us with opened struct file waiting for __fput() - execve() |
| * won't work without that. Please, don't add more callers without |
| * very good reasons; in particular, never call that with locks |
| * held and never call that from a thread that might need to do |
| * some work on any kind of umount. |
| */ |
| void flush_delayed_fput(void) |
| { |
| delayed_fput(NULL); |
| } |
| |
| static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput); |
| |
| void fput(struct file *file) |
| { |
| if (atomic_long_dec_and_test(&file->f_count)) { |
| struct task_struct *task = current; |
| |
| if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) { |
| init_task_work(&file->f_u.fu_rcuhead, ____fput); |
| if (!task_work_add(task, &file->f_u.fu_rcuhead, true)) |
| return; |
| /* |
| * After this task has run exit_task_work(), |
| * task_work_add() will fail. Fall through to delayed |
| * fput to avoid leaking *file. |
| */ |
| } |
| |
| if (llist_add(&file->f_u.fu_llist, &delayed_fput_list)) |
| schedule_delayed_work(&delayed_fput_work, 1); |
| } |
| } |
| |
| /* |
| * synchronous analog of fput(); for kernel threads that might be needed |
| * in some umount() (and thus can't use flush_delayed_fput() without |
| * risking deadlocks), need to wait for completion of __fput() and know |
| * for this specific struct file it won't involve anything that would |
| * need them. Use only if you really need it - at the very least, |
| * don't blindly convert fput() by kernel thread to that. |
| */ |
| void __fput_sync(struct file *file) |
| { |
| if (atomic_long_dec_and_test(&file->f_count)) { |
| struct task_struct *task = current; |
| BUG_ON(!(task->flags & PF_KTHREAD)); |
| __fput(file); |
| } |
| } |
| |
| EXPORT_SYMBOL(fput); |
| |
| void put_filp(struct file *file) |
| { |
| if (atomic_long_dec_and_test(&file->f_count)) { |
| security_file_free(file); |
| file_free(file); |
| } |
| } |
| |
| void __init files_init(void) |
| { |
| filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, |
| SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
| percpu_counter_init(&nr_files, 0, GFP_KERNEL); |
| } |
| |
| /* |
| * One file with associated inode and dcache is very roughly 1K. Per default |
| * do not use more than 10% of our memory for files. |
| */ |
| void __init files_maxfiles_init(void) |
| { |
| unsigned long n; |
| unsigned long memreserve = (totalram_pages - nr_free_pages()) * 3/2; |
| |
| memreserve = min(memreserve, totalram_pages - 1); |
| n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10; |
| |
| files_stat.max_files = max_t(unsigned long, n, NR_FILE); |
| } |