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authorLinus Torvalds <torvalds@linux-foundation.org>2010-04-10 10:36:19 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-04-12 17:53:59 -0700
commitd0e9fe1758f222f13ec893f856552d81a10d266d (patch)
tree93e55a2e26c2b2f40b6d9142515fd14de8eb6647 /mm/rmap.c
parent0eddb519b9127c73d53db4bf3ec1d45b13f844d1 (diff)
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Simplify and comment on anon_vma re-use for anon_vma_prepare()
This changes the anon_vma reuse case to require that we only reuse simple anon_vma's - ie the case when the vma only has a single anon_vma associated with it. This means that a reuse of an anon_vma from an adjacent vma will always guarantee that both vma's are associated not only with the same anon_vma, they will also have the same anon_vma chain (of just a single entry in this case). And since anon_vma re-use was the only case where the same anon_vma might be associated with different chains of anon_vma's, we now have the case that every vma that shares the same anon_vma will always also have the same chain. That makes it much easier to think about merging vma's that share the same anon_vma's: you can always just drop the other anon_vma chain in anon_vma_merge() since you know that they are always identical. This also splits up the function to validate the anon_vma re-use, and adds a lot of commentary about the possible races. Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Tested-by: Borislav Petkov <bp@alien8.de> [ "That didn't fix it" ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
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