From d445bd9cec1a850c2100fcf53684c13b3fd934f2 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Tue, 15 Jan 2019 13:27:01 -0500 Subject: [PATCH] dm thin: fix passdown_double_checking_shared_status() 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 Signed-off-by: Mike Snitzer --- 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(-) diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c index 20b0776e39ef..ed3caceaed07 100644 --- a/drivers/md/dm-thin-metadata.c +++ b/drivers/md/dm-thin-metadata.c @@ -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; diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h index 35e954ea20a9..f6be0d733c20 100644 --- 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 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); diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index dadd9696340c..ca8af21bf644 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -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; } -- 2.11.0