4.9-stable review patch. If anyone has any objections, please let me know.
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From: Joe Thornber ejt@redhat.com
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 | 4 ++-- drivers/md/dm-thin-metadata.h | 2 +- drivers/md/dm-thin.c | 10 +++++----- 3 files changed, 8 insertions(+), 8 deletions(-)
--- a/drivers/md/dm-thin-metadata.c +++ b/drivers/md/dm-thin-metadata.c @@ -1689,7 +1689,7 @@ int dm_thin_remove_range(struct dm_thin_ 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; @@ -1697,7 +1697,7 @@ int dm_pool_block_is_used(struct dm_pool 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; --- a/drivers/md/dm-thin-metadata.h +++ b/drivers/md/dm-thin-metadata.h @@ -195,7 +195,7 @@ int dm_pool_get_metadata_dev_size(struct
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); --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1017,7 +1017,7 @@ static void passdown_double_checking_sha * 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; @@ -1027,11 +1027,11 @@ static void passdown_double_checking_sha 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; }
@@ -1040,11 +1040,11 @@ static void passdown_double_checking_sha
/* 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; }