tree aff4632c89079be43353a32b2a15b85ea15e858f
parent 4e7f07396a5f093859a29c83a4dfc9e8fd34b4e0
author Linus Torvalds <torvalds@linux-foundation.org> 1536832668 -1000
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1537390037 +0200

mm: get rid of vmacache_flush_all() entirely

commit 7a9cdebdcc17e426fb5287e4a82db1dfe86339b2 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>