| Message ID | 20241022071222.778553-1-mtsai@redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Mikulas Patocka |
| Headers | show |
| Series | dm cache: fix OOB and error handling in cache creation and resizing | expand |
ack On Tue, Oct 22, 2024 at 8:12 AM Ming-Hung Tsai <mtsai@redhat.com> wrote: > > When creating a cache device, the actual size of the cache origin might > be greater than the specified cache target length. In such case, the > number of origin blocks should match the cache target length, not the > full size of the origin device, since access beyond the cache target is > not possible. This issue occurs when reducing the origin device size > using lvm, as lvreduce preloads the new cache table before resuming the > cache origin, which can result in incorrect sizes for the discard bitset > and smq hotspot blocks. > > Reproduce steps: > > 1. create a cache device consists of 4096 origin blocks > > dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" > dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" > dmsetup create corig --table "0 524288 linear /dev/sdc 262144" > dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct > dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \ > /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" > > 2. reduce the cache origin to 2048 oblocks, in lvreduce's approach > > dmsetup reload corig --table "0 262144 linear /dev/sdc 262144" > dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ > /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" > dmsetup suspend cache > dmsetup suspend corig > dmsetup suspend cdata > dmsetup suspend cmeta > dmsetup resume corig > dmsetup resume cdata > dmsetup resume cmeta > dmsetup resume cache > > 3. shutdown the cache, and check the number of discard blocks in > superblock. The value is expected to be 2048, but actually is 4096. > > dmsetup remove cache corig cdata cmeta > dd if=/dev/sdc bs=1c count=8 skip=224 2>/dev/null | hexdump -e '1/8 "%u\n"' > > Fix by correcting the origin_blocks initialization in cache_create and > removing the unused origin_sectors from struct cache_args accordingly. > > Signed-off-by: Ming-Hung Tsai <mtsai@redhat.com> > Fixes: c6b4fcbad044 ("dm: add cache target") > --- > drivers/md/dm-cache-target.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c > index aaeeabfab09b..90772b42c234 100644 > --- a/drivers/md/dm-cache-target.c > +++ b/drivers/md/dm-cache-target.c > @@ -2003,7 +2003,6 @@ struct cache_args { > sector_t cache_sectors; > > struct dm_dev *origin_dev; > - sector_t origin_sectors; > > uint32_t block_size; > > @@ -2084,6 +2083,7 @@ static int parse_cache_dev(struct cache_args *ca, struct dm_arg_set *as, > static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as, > char **error) > { > + sector_t origin_sectors; > int r; > > if (!at_least_one_arg(as, error)) > @@ -2096,8 +2096,8 @@ static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as, > return r; > } > > - ca->origin_sectors = get_dev_size(ca->origin_dev); > - if (ca->ti->len > ca->origin_sectors) { > + origin_sectors = get_dev_size(ca->origin_dev); > + if (ca->ti->len > origin_sectors) { > *error = "Device size larger than cached device"; > return -EINVAL; > } > @@ -2407,7 +2407,7 @@ static int cache_create(struct cache_args *ca, struct cache **result) > > ca->metadata_dev = ca->origin_dev = ca->cache_dev = NULL; > > - origin_blocks = cache->origin_sectors = ca->origin_sectors; > + origin_blocks = cache->origin_sectors = ti->len; > origin_blocks = block_div(origin_blocks, ca->block_size); > cache->origin_blocks = to_oblock(origin_blocks); > > -- > 2.47.0 >
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index aaeeabfab09b..90772b42c234 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -2003,7 +2003,6 @@ struct cache_args { sector_t cache_sectors; struct dm_dev *origin_dev; - sector_t origin_sectors; uint32_t block_size; @@ -2084,6 +2083,7 @@ static int parse_cache_dev(struct cache_args *ca, struct dm_arg_set *as, static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as, char **error) { + sector_t origin_sectors; int r; if (!at_least_one_arg(as, error)) @@ -2096,8 +2096,8 @@ static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as, return r; } - ca->origin_sectors = get_dev_size(ca->origin_dev); - if (ca->ti->len > ca->origin_sectors) { + origin_sectors = get_dev_size(ca->origin_dev); + if (ca->ti->len > origin_sectors) { *error = "Device size larger than cached device"; return -EINVAL; } @@ -2407,7 +2407,7 @@ static int cache_create(struct cache_args *ca, struct cache **result) ca->metadata_dev = ca->origin_dev = ca->cache_dev = NULL; - origin_blocks = cache->origin_sectors = ca->origin_sectors; + origin_blocks = cache->origin_sectors = ti->len; origin_blocks = block_div(origin_blocks, ca->block_size); cache->origin_blocks = to_oblock(origin_blocks);
When creating a cache device, the actual size of the cache origin might be greater than the specified cache target length. In such case, the number of origin blocks should match the cache target length, not the full size of the origin device, since access beyond the cache target is not possible. This issue occurs when reducing the origin device size using lvm, as lvreduce preloads the new cache table before resuming the cache origin, which can result in incorrect sizes for the discard bitset and smq hotspot blocks. Reproduce steps: 1. create a cache device consists of 4096 origin blocks dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524288 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. reduce the cache origin to 2048 oblocks, in lvreduce's approach dmsetup reload corig --table "0 262144 linear /dev/sdc 262144" dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" dmsetup suspend cache dmsetup suspend corig dmsetup suspend cdata dmsetup suspend cmeta dmsetup resume corig dmsetup resume cdata dmsetup resume cmeta dmsetup resume cache 3. shutdown the cache, and check the number of discard blocks in superblock. The value is expected to be 2048, but actually is 4096. dmsetup remove cache corig cdata cmeta dd if=/dev/sdc bs=1c count=8 skip=224 2>/dev/null | hexdump -e '1/8 "%u\n"' Fix by correcting the origin_blocks initialization in cache_create and removing the unused origin_sectors from struct cache_args accordingly. Signed-off-by: Ming-Hung Tsai <mtsai@redhat.com> Fixes: c6b4fcbad044 ("dm: add cache target") --- drivers/md/dm-cache-target.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)