NothingOSS/android_kernel_msm-6.1_nothing_sm7635
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

UPSTREAM: mm: fall back to mmap_lock if vma->anon_vma is not yet set

Browse source 
When vma->anon_vma is not set, page fault handler will set it by either
reusing anon_vma of an adjacent VMA if VMAs are compatible or by
allocating a new one.  find_mergeable_anon_vma() walks VMA tree to find a
compatible adjacent VMA and that requires not only the faulting VMA to be
stable but also the tree structure and other VMAs inside that tree.
Therefore locking just the faulting VMA is not enough for this search.
Fall back to taking mmap_lock when vma->anon_vma is not set.  This
situation happens only on the first page fault and should not affect
overall performance.

Link: https://lkml.kernel.org/r/20230227173632.3292573-25-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit 2ac0af1b66e3b66307f53b1cc446514308ec466d)

Bug: 161210518
Change-Id: Iafacad5bda7bb138b290f38421a22d828051b067
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Suren Baghdasaryan 2023-02-27 09:36:23 -08:00 • committed by Carlos Llamas
parent 5949b78f6c
commit c06661eab5
1 changed files with 4 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

4
mm/memory.c
View file

@ -5284,6 +5284,10 @@ retry:
if (!vma_is_anonymous(vma))
goto inval;
/* find_mergeable_anon_vma uses adjacent vmas which are not locked */
if (!vma->anon_vma)
goto inval;
if (!vma_start_read(vma))
goto inval;