tree 6b498fc08174b16b9fa1f44cce5d08d884eec49b
parent 22fe404218156328a27e66349b1175cd0baa4990
author Andi Kleen <andi@firstfloor.org> 1253304347 -0700
committer Al Viro <viro@zeniv.linux.org.uk> 1253792846 -0400

vfs: optimization for touch_atime()

Some benchmark testing shows touch_atime to be high up in profile logs for
IO intensive workloads.  Most likely that's due to the lock in
mnt_want_write().  Unfortunately touch_atime first takes the lock, and
then does all the other tests that could avoid atime updates (like noatime
or relatime).

Do it the other way round -- first try to avoid the update and only then
if that didn't succeed take the lock.  That works because none of the
atime avoidance tests rely on locking.

This also eliminates a goto.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Valerie Aurora <vaurora@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>