tree 5e07371622cf637eacdadeb676acd650796c45b2
parent 20eb4c4bcab0f7ce05051ed5b81ee33229e63565
author Linus Torvalds <torvalds@linux-foundation.org> 1536832668 -1000
committer ChromeOS Commit Bot <chromeos-commit-bot@chromium.org> 1543946297 +0000

BACKPORT: mm: get rid of vmacache_flush_all() entirely

Jann Horn points out that the vmacache_flush_all() function is not only
potentially expensive, it's buggy too.  It also happens to be entirely
unnecessary, because the sequence number overflow case can be avoided by
simply making the sequence number be 64-bit.  That doesn't even grow the
data structures in question, because the other adjacent fields are
already 64-bit.

So simplify the whole thing by just making the sequence number overflow
case go away entirely, which gets rid of all the complications and makes
the code faster too.  Win-win.

[ Oleg Nesterov points out that the VMACACHE_FULL_FLUSHES statistics
  also just goes away entirely with this ]

Reported-by: Jann Horn <jannh@google.com>
Suggested-by: Will Deacon <will.deacon@arm.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 7a9cdebdcc17e426fb5287e4a82db1dfe86339b2)

Conflicts:
	include/linux/mm_types.h
	mm/debug.c

BUG=b:120193974
TEST=lakitu-release tryjob

Change-Id: I605ceb43288d4ddb0c5febd816816ca18fd68939
Reviewed-on: https://chromium-review.googlesource.com/c/1359796
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Commit-Queue: Daniel Wang <wonderfly@google.com>
Tested-by: Daniel Wang <wonderfly@google.com>