Commit d445bd9c authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

dm thin: fix passdown_double_checking_shared_status() 



Commit 00a0ea33 ("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 00a0ea33
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: 00a0ea33 ("dm thin: do not queue freed thin mapping for next stage processing")
Cc: stable@vger.kernel.org # 4.9+
Reported-by: default avatar <ryan.p.norwood@gmail.com>
Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 1856b9f7

drivers/md/dm-thin-metadata.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

drivers/md/dm-thin-metadata.h

+1 −1
Original line number Diff line number Diff line
@@ -195,7 +195,7 @@ int dm_pool_get_metadata_dev_size(struct dm_pool_metadata *pmd, 


int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result);



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 dm_pool_inc_data_range(struct dm_pool_metadata *pmd, dm_block_t b, dm_block_t e);

int dm_pool_dec_data_range(struct dm_pool_metadata *pmd, dm_block_t b, dm_block_t e);

drivers/md/dm-thin.c

+5 −5
Original line number Diff line number Diff line
@@ -1048,7 +1048,7 @@ static void passdown_double_checking_shared_status(struct dm_thin_new_mapping *m 
	 * passdown we have to check that these blocks are now unused.

	 */

	int r = 0;

	bool used = true;

	bool shared = true;

	struct thin_c *tc = m->tc;

	struct pool *pool = tc->pool;

	dm_block_t b = m->data_block, e, end = m->data_block + m->virt_end - m->virt_begin;
@@ -1058,11 +1058,11 @@ static void passdown_double_checking_shared_status(struct dm_thin_new_mapping *m 
	while (b != end) {

		/* find start of unmapped run */

		for (; b < end; b++) {

			r = dm_pool_block_is_used(pool->pmd, b, &used);

			r = dm_pool_block_is_shared(pool->pmd, b, &shared);

			if (r)

				goto out;



			if (!used)

			if (!shared)

				break;

		}
@@ -1071,11 +1071,11 @@ static void passdown_double_checking_shared_status(struct dm_thin_new_mapping *m 


		/* find end of run */

		for (e = b + 1; e != end; e++) {

			r = dm_pool_block_is_used(pool->pmd, e, &used);

			r = dm_pool_block_is_shared(pool->pmd, e, &shared);

			if (r)

				goto out;



			if (used)

			if (shared)

				break;

		}

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