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dm thin: fix passdown_double_checking_shared_status()

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Commit 00a0ea33b4 ("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 00a0ea33b4
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: 00a0ea33b4 ("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>
This commit is contained in:
Joe Thornber
2019-01-15 13:27:01 -05:00
committed by Mike Snitzer
parent 1856b9f7bc
commit d445bd9cec
3 changed files with 8 additions and 8 deletions
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4
drivers/md/dm-thin-metadata.c
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@@ -1678,7 +1678,7 @@ int dm_thin_remove_range(struct dm_thin_device *td,
return r;
}
int dm_pool_block_is_used(struct dm_pool_metadata *pmd, dm_block_t b, bool *result)
int dm_pool_block_is_shared(struct dm_pool_metadata *pmd, dm_block_t b, bool *result)
{
int r;
uint32_t ref_count;
@@ -1686,7 +1686,7 @@ int dm_pool_block_is_used(struct dm_pool_metadata *pmd, dm_block_t b, bool *resu
down_read(&pmd->root_lock);
r = dm_sm_get_count(pmd->data_sm, b, &ref_count);
if (!r)
*result = (ref_count != 0);
*result = (ref_count > 1);
up_read(&pmd->root_lock);
return r;