When using block size greater than 512 bytes, the dm-integrity target allocates journal space inefficiently, it allocates one entry for each 512-byte chunk of data, fills entries for each block of data and leaves the remaining entries unused. This doesn't cause data corruption, but it causes severe performance degradation.
This patch fixes the journal allocation. As a safety it also adds BUG that fires if the variables representing journal usage get out of sync (it's better to crash than continue and corrupt data, so BUG is justified). Signed-off-by: Mikulas Patocka <[email protected]> Cc: [email protected] Fixes: 7eada909bfd7 ("dm: add integrity target") --- drivers/md/dm-integrity.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) Index: linux-2.6/drivers/md/dm-integrity.c =================================================================== --- linux-2.6.orig/drivers/md/dm-integrity.c +++ linux-2.6/drivers/md/dm-integrity.c @@ -1589,14 +1589,14 @@ retry: unsigned next_entry, i, pos; unsigned ws, we; - dio->range.n_sectors = min(dio->range.n_sectors, ic->free_sectors); + dio->range.n_sectors = min(dio->range.n_sectors, ic->free_sectors << ic->sb->log2_sectors_per_block); if (unlikely(!dio->range.n_sectors)) goto sleep; - ic->free_sectors -= dio->range.n_sectors; + ic->free_sectors -= dio->range.n_sectors >> ic->sb->log2_sectors_per_block; journal_section = ic->free_section; journal_entry = ic->free_section_entry; - next_entry = ic->free_section_entry + dio->range.n_sectors; + next_entry = ic->free_section_entry + (dio->range.n_sectors >> ic->sb->log2_sectors_per_block); ic->free_section_entry = next_entry % ic->journal_section_entries; ic->free_section += next_entry / ic->journal_section_entries; ic->n_uncommitted_sections += next_entry / ic->journal_section_entries; @@ -1727,6 +1727,7 @@ static void pad_uncommitted(struct dm_in wraparound_section(ic, &ic->free_section); ic->n_uncommitted_sections++; } + BUG_ON((ic->n_uncommitted_sections + ic->n_committed_sections) * ic->journal_section_entries + ic->free_sectors != ic->journal_sections * ic->journal_section_entries); } static void integrity_commit(struct work_struct *w) -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
