path: root/mm/mlock.c
diff options
authorLinus Torvalds <>2011-04-12 14:15:51 -0700
committerLinus Torvalds <>2011-04-12 14:15:51 -0700
commit95042f9eb78a8d9a17455e2ef263f2f310ecef15 (patch)
treeac9fe0a5e17c4b94b18b84338ffbeca2cee140cb /mm/mlock.c
parentbe85bccaa5aa5a11dcaf85f9e945ffefd253f631 (diff)
vm: fix mlock() on stack guard page
Commit 53a7706d5ed8 ("mlock: do not hold mmap_sem for extended periods of time") changed mlock() to care about the exact number of pages that __get_user_pages() had brought it. Before, it would only care about errors. And that doesn't work, because we also handled one page specially in __mlock_vma_pages_range(), namely the stack guard page. So when that case was handled, the number of pages that the function returned was off by one. In particular, it could be zero, and then the caller would end up not making any progress at all. Rather than try to fix up that off-by-one error for the mlock case specially, this just moves the logic to handle the stack guard page into__get_user_pages() itself, thus making all the counts come out right automatically. Reported-by: Robert Święcki <> Cc: Hugh Dickins <> Cc: Oleg Nesterov <> Cc: Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/mlock.c')
1 files changed, 0 insertions, 13 deletions
diff --git a/mm/mlock.c b/mm/mlock.c
index 2689a08c79af..6b55e3efe0df 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -135,13 +135,6 @@ void munlock_vma_page(struct page *page)
-static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
- return (vma->vm_flags & VM_GROWSDOWN) &&
- (vma->vm_start == addr) &&
- !vma_stack_continue(vma->vm_prev, addr);
* __mlock_vma_pages_range() - mlock a range of pages in the vma.
* @vma: target vma
@@ -188,12 +181,6 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
if (vma->vm_flags & VM_LOCKED)
gup_flags |= FOLL_MLOCK;
- /* We don't try to access the guard page of a stack vma */
- if (stack_guard_page(vma, start)) {
- addr += PAGE_SIZE;
- nr_pages--;
- }
return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
NULL, NULL, nonblocking);