From: Nikos Tsironis ntsironis@arrikto.com
commit de89afc1e40fdfa5f8b666e5d07c43d21a1d3be0 upstream.
Following a system crash, dm-era fails to recover the committed writeset for the current era, leading to lost writes. That is, we lose the information about what blocks were written during the affected era.
dm-era assumes that the writeset of the current era is archived when the device is suspended. So, when resuming the device, it just moves on to the next era, ignoring the committed writeset.
This assumption holds when the device is properly shut down. But, when the system crashes, the code that suspends the target never runs, so the writeset for the current era is not archived.
There are three issues that cause the committed writeset to get lost:
1. dm-era doesn't load the committed writeset when opening the metadata 2. The code that resizes the metadata wipes the information about the committed writeset (assuming it was loaded at step 1) 3. era_preresume() starts a new era, without taking into account that the current era might not have been archived, due to a system crash.
To fix this:
1. Load the committed writeset when opening the metadata 2. Fix the code that resizes the metadata to make sure it doesn't wipe the loaded writeset 3. Fix era_preresume() to check for a loaded writeset and archive it, before starting a new era.
Fixes: eec40579d84873 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis ntsironis@arrikto.com Signed-off-by: Mike Snitzer snitzer@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/dm-era-target.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)
--- a/drivers/md/dm-era-target.c +++ b/drivers/md/dm-era-target.c @@ -70,8 +70,6 @@ static size_t bitset_size(unsigned nr_bi */ static int writeset_alloc(struct writeset *ws, dm_block_t nr_blocks) { - ws->md.nr_bits = nr_blocks; - ws->md.root = INVALID_WRITESET_ROOT; ws->bits = vzalloc(bitset_size(nr_blocks)); if (!ws->bits) { DMERR("%s: couldn't allocate in memory bitset", __func__); @@ -84,12 +82,14 @@ static int writeset_alloc(struct writese /* * Wipes the in-core bitset, and creates a new on disk bitset. */ -static int writeset_init(struct dm_disk_bitset *info, struct writeset *ws) +static int writeset_init(struct dm_disk_bitset *info, struct writeset *ws, + dm_block_t nr_blocks) { int r;
- memset(ws->bits, 0, bitset_size(ws->md.nr_bits)); + memset(ws->bits, 0, bitset_size(nr_blocks));
+ ws->md.nr_bits = nr_blocks; r = setup_on_disk_bitset(info, ws->md.nr_bits, &ws->md.root); if (r) { DMERR("%s: setup_on_disk_bitset failed", __func__); @@ -579,6 +579,7 @@ static int open_metadata(struct era_meta md->nr_blocks = le32_to_cpu(disk->nr_blocks); md->current_era = le32_to_cpu(disk->current_era);
+ ws_unpack(&disk->current_writeset, &md->current_writeset->md); md->writeset_tree_root = le64_to_cpu(disk->writeset_tree_root); md->era_array_root = le64_to_cpu(disk->era_array_root); md->metadata_snap = le64_to_cpu(disk->metadata_snap); @@ -871,7 +872,6 @@ static int metadata_era_archive(struct e }
ws_pack(&md->current_writeset->md, &value); - md->current_writeset->md.root = INVALID_WRITESET_ROOT;
keys[0] = md->current_era; __dm_bless_for_disk(&value); @@ -883,6 +883,7 @@ static int metadata_era_archive(struct e return r; }
+ md->current_writeset->md.root = INVALID_WRITESET_ROOT; md->archived_writesets = true;
return 0; @@ -899,7 +900,7 @@ static int metadata_new_era(struct era_m int r; struct writeset *new_writeset = next_writeset(md);
- r = writeset_init(&md->bitset_info, new_writeset); + r = writeset_init(&md->bitset_info, new_writeset, md->nr_blocks); if (r) { DMERR("%s: writeset_init failed", __func__); return r; @@ -952,7 +953,7 @@ static int metadata_commit(struct era_me int r; struct dm_block *sblock;
- if (md->current_writeset->md.root != SUPERBLOCK_LOCATION) { + if (md->current_writeset->md.root != INVALID_WRITESET_ROOT) { r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root, &md->current_writeset->md.root); if (r) { @@ -1582,7 +1583,7 @@ static int era_preresume(struct dm_targe
start_worker(era);
- r = in_worker0(era, metadata_new_era); + r = in_worker0(era, metadata_era_rollover); if (r) { DMERR("%s: metadata_era_rollover failed", __func__); return r;