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| author | Johannes Weiner <hannes@cmpxchg.org> | 2013-02-22 16:35:20 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-02-23 17:50:20 -0800 |
| commit | 4805b02e90187c68d8f4e3305c3482b797e35809 (patch) | |
| tree | 65d574e7ee8068597f59b712417b6ecf700d1a49 /mm | |
| parent | e3790144c9091631a18564aa64db8a971da02c41 (diff) | |
| download | linux-4805b02e90187c68d8f4e3305c3482b797e35809.tar.bz2 | |
mm/mlock.c: document scary-looking stack expansion mlock chain
The fact that mlock calls get_user_pages, and get_user_pages might call
mlock when expanding a stack looks like a potential recursion.
However, mlock makes sure the requested range is already contained
within a vma, so no stack expansion will actually happen from mlock.
Should this ever change: the stack expansion mlocks only the newly
expanded range and so will not result in recursive expansion.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/mlock.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/mlock.c b/mm/mlock.c index d6378feb2950..38db3b094105 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -185,6 +185,10 @@ long __mlock_vma_pages_range(struct vm_area_struct *vma, if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) gup_flags |= FOLL_FORCE; + /* + * We made sure addr is within a VMA, so the following will + * not result in a stack expansion that recurses back here. + */ return __get_user_pages(current, mm, addr, nr_pages, gup_flags, NULL, NULL, nonblocking); } |