[PATCH] mm: pte_offset_map_lock loops
Convert those common loops using page_table_lock on the outside and
pte_offset_map within to use just pte_offset_map_lock within instead.
These all hold mmap_sem (some exclusively, some not), so at no level can a
page table be whipped away from beneath them. But whereas pte_alloc loops
tested with the "atomic" pmd_present, these loops are testing with pmd_none,
which on i386 PAE tests both lower and upper halves.
That's now unsafe, so add a cast into pmd_none to test only the vital lower
half: we lose a little sensitivity to a corrupt middle directory, but not
enough to worry about. It appears that i386 and UML were the only
architectures vulnerable in this way, and pgd and pud no problem.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 11d824f..902d4c9 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -228,9 +228,9 @@
{
pte_t *orig_pte;
pte_t *pte;
+ spinlock_t *ptl;
- spin_lock(&vma->vm_mm->page_table_lock);
- orig_pte = pte = pte_offset_map(pmd, addr);
+ orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
do {
unsigned long pfn;
unsigned int nid;
@@ -246,8 +246,7 @@
if (!node_isset(nid, *nodes))
break;
} while (pte++, addr += PAGE_SIZE, addr != end);
- pte_unmap(orig_pte);
- spin_unlock(&vma->vm_mm->page_table_lock);
+ pte_unmap_unlock(orig_pte, ptl);
return addr != end;
}
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 672a76f..17a2b52 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -29,8 +29,9 @@
unsigned long addr, unsigned long end, pgprot_t newprot)
{
pte_t *pte;
+ spinlock_t *ptl;
- pte = pte_offset_map(pmd, addr);
+ pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
do {
if (pte_present(*pte)) {
pte_t ptent;
@@ -44,7 +45,7 @@
lazy_mmu_prot_update(ptent);
}
} while (pte++, addr += PAGE_SIZE, addr != end);
- pte_unmap(pte - 1);
+ pte_unmap_unlock(pte - 1, ptl);
}
static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
@@ -88,7 +89,6 @@
BUG_ON(addr >= end);
pgd = pgd_offset(mm, addr);
flush_cache_range(vma, addr, end);
- spin_lock(&mm->page_table_lock);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
@@ -96,7 +96,6 @@
change_pud_range(mm, pgd, addr, next, newprot);
} while (pgd++, addr = next, addr != end);
flush_tlb_range(vma, start, end);
- spin_unlock(&mm->page_table_lock);
}
static int
diff --git a/mm/msync.c b/mm/msync.c
index 8603954..0e040e9 100644
--- a/mm/msync.c
+++ b/mm/msync.c
@@ -17,28 +17,22 @@
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
-/*
- * Called with mm->page_table_lock held to protect against other
- * threads/the swapper from ripping pte's out from under us.
- */
-
static void msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end)
{
- struct mm_struct *mm = vma->vm_mm;
pte_t *pte;
+ spinlock_t *ptl;
int progress = 0;
again:
- pte = pte_offset_map(pmd, addr);
+ pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
do {
unsigned long pfn;
struct page *page;
if (progress >= 64) {
progress = 0;
- if (need_resched() ||
- need_lockbreak(&mm->page_table_lock))
+ if (need_resched() || need_lockbreak(ptl))
break;
}
progress++;
@@ -58,8 +52,8 @@
set_page_dirty(page);
progress += 3;
} while (pte++, addr += PAGE_SIZE, addr != end);
- pte_unmap(pte - 1);
- cond_resched_lock(&mm->page_table_lock);
+ pte_unmap_unlock(pte - 1, ptl);
+ cond_resched();
if (addr != end)
goto again;
}
@@ -97,7 +91,6 @@
static void msync_page_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end)
{
- struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd;
unsigned long next;
@@ -110,16 +103,14 @@
return;
BUG_ON(addr >= end);
- pgd = pgd_offset(mm, addr);
+ pgd = pgd_offset(vma->vm_mm, addr);
flush_cache_range(vma, addr, end);
- spin_lock(&mm->page_table_lock);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
msync_pud_range(vma, pgd, addr, next);
} while (pgd++, addr = next, addr != end);
- spin_unlock(&mm->page_table_lock);
}
/*
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 296e0bb..510f003 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -401,8 +401,6 @@
* No need to decide whether this PTE shares the swap entry with others,
* just let do_wp_page work it out if a write is requested later - to
* force COW, vm_page_prot omits write permission from any private vma.
- *
- * vma->vm_mm->page_table_lock is held.
*/
static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
unsigned long addr, swp_entry_t entry, struct page *page)
@@ -424,23 +422,25 @@
unsigned long addr, unsigned long end,
swp_entry_t entry, struct page *page)
{
- pte_t *pte;
pte_t swp_pte = swp_entry_to_pte(entry);
+ pte_t *pte;
+ spinlock_t *ptl;
+ int found = 0;
- pte = pte_offset_map(pmd, addr);
+ pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
do {
/*
* swapoff spends a _lot_ of time in this loop!
* Test inline before going to call unuse_pte.
*/
if (unlikely(pte_same(*pte, swp_pte))) {
- unuse_pte(vma, pte, addr, entry, page);
- pte_unmap(pte);
- return 1;
+ unuse_pte(vma, pte++, addr, entry, page);
+ found = 1;
+ break;
}
} while (pte++, addr += PAGE_SIZE, addr != end);
- pte_unmap(pte - 1);
- return 0;
+ pte_unmap_unlock(pte - 1, ptl);
+ return found;
}
static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
@@ -522,12 +522,10 @@
down_read(&mm->mmap_sem);
lock_page(page);
}
- spin_lock(&mm->page_table_lock);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (vma->anon_vma && unuse_vma(vma, entry, page))
break;
}
- spin_unlock(&mm->page_table_lock);
up_read(&mm->mmap_sem);
/*
* Currently unuse_mm cannot fail, but leave error handling
