rbd: make exists flag atomic
authorAlex Elder <elder@inktank.com>
Fri, 9 Nov 2012 14:43:15 +0000 (08:43 -0600)
committerAlex Elder <elder@inktank.com>
Thu, 17 Jan 2013 21:52:00 +0000 (15:52 -0600)
commitd78b650a595e23e5a115d332e3c37e019baf7703
treed2fd5bb83a6b32f90d6cd802379feedc136d52b4
parentb395e8b5b8f06399e3fe3ee016c9cf41ff665efc
rbd: make exists flag atomic

The rbd_device->exists field can be updated asynchronously, changing
from set to clear if a mapped snapshot disappears from the base
image's snapshot context.

Currently, value of the "exists" flag is only read and modified
under protection of the header semaphore, but that will change with
the next patch.  Making it atomic ensures this won't be a problem
because the a the non-existence of device will be immediately known.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
drivers/block/rbd.c