dm thin: fix passdown_double_checking_shared_status()
authorJoe Thornber <ejt@redhat.com>
Tue, 15 Jan 2019 18:27:01 +0000 (13:27 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 31 Jan 2019 07:13:45 +0000 (08:13 +0100)
commit294710ddfc480aee277325cee8b54afa0c514e43
treea7eed7d8869c625dc7b85073dc5179572ccb7bd3
parent1c285c34a509ddfc83be425d8305a6d94d502208
dm thin: fix passdown_double_checking_shared_status()

commit d445bd9cec1a850c2100fcf53684c13b3fd934f2 upstream.

Commit 00a0ea33b495 ("dm thin: do not queue freed thin mapping for next
stage processing") changed process_prepared_discard_passdown_pt1() to
increment all the blocks being discarded until after the passdown had
completed to avoid them being prematurely reused.

IO issued to a thin device that breaks sharing with a snapshot, followed
by a discard issued to snapshot(s) that previously shared the block(s),
results in passdown_double_checking_shared_status() being called to
iterate through the blocks double checking their reference count is zero
and issuing the passdown if so.  So a side effect of commit 00a0ea33b495
is passdown_double_checking_shared_status() was broken.

Fix this by checking if the block reference count is greater than 1.
Also, rename dm_pool_block_is_used() to dm_pool_block_is_shared().

Fixes: 00a0ea33b495 ("dm thin: do not queue freed thin mapping for next stage processing")
Cc: stable@vger.kernel.org # 4.9+
Reported-by: ryan.p.norwood@gmail.com
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/md/dm-thin-metadata.c
drivers/md/dm-thin-metadata.h
drivers/md/dm-thin.c