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dm thin: fix passdown_double_checking_shared_status() 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/md/dm-thin-metadata.c
View File

@ -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;

2
drivers/md/dm-thin-metadata.h
View File

@ -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);

10
drivers/md/dm-thin.c
View File

@ -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;
}