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authorJohannes Weiner <hannes@cmpxchg.org>2013-02-22 16:35:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-23 17:50:20 -0800
commit4805b02e90187c68d8f4e3305c3482b797e35809 (patch)
tree65d574e7ee8068597f59b712417b6ecf700d1a49 /mm/mlock.c
parentmm: refactor inactive_file_is_low() to use get_lru_size() (diff)
downloadlinux-dev-4805b02e90187c68d8f4e3305c3482b797e35809.tar.xz
linux-dev-4805b02e90187c68d8f4e3305c3482b797e35809.zip
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 '')
-rw-r--r--mm/mlock.c4
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);
}