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dm cache: share cache-metadata object across inactive and active DM tables 

If a DM table is reloaded with an inactive table when the device is not
suspended (normal procedure for LVM2), then there will be two dm-bufio
objects that can diverge.  This can lead to a situation where the
inactive table uses bufio to read metadata at the same time the active
table writes metadata -- resulting in the inactive table having stale
metadata buffers once it is promoted to the active table slot.

Fix this by using reference counting and a global list of cache metadata
objects to ensure there is only one metadata object per metadata device.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Joe Thornber 2015-01-23 10:00:07 +00:00 committed by Mike Snitzer
parent 5164bece16
commit 9b1cc9f251
1 changed files with 95 additions and 6 deletions
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101
drivers/md/dm-cache-metadata.c
View File

@ -94,6 +94,9 @@ struct cache_disk_superblock {
} __packed;
struct dm_cache_metadata {
atomic_t ref_count;
struct list_head list;
struct block_device *bdev;
struct dm_block_manager *bm;
struct dm_space_map *metadata_sm;
@ -669,10 +672,10 @@ static void unpack_value(__le64 value_le, dm_oblock_t *block, unsigned *flags)
/*----------------------------------------------------------------*/
struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
sector_t data_block_size,
bool may_format_device,
size_t policy_hint_size)
static struct dm_cache_metadata *metadata_open(struct block_device *bdev,
sector_t data_block_size,
bool may_format_device,
size_t policy_hint_size)
{
int r;
struct dm_cache_metadata *cmd;
@ -683,6 +686,7 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
return NULL;
}
atomic_set(&cmd->ref_count, 1);
init_rwsem(&cmd->root_lock);
cmd->bdev = bdev;
cmd->data_block_size = data_block_size;
@ -705,10 +709,95 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
return cmd;
}
/*
* We keep a little list of ref counted metadata objects to prevent two
* different target instances creating separate bufio instances. This is
* an issue if a table is reloaded before the suspend.
*/
static DEFINE_MUTEX(table_lock);
static LIST_HEAD(table);
static struct dm_cache_metadata *lookup(struct block_device *bdev)
{
struct dm_cache_metadata *cmd;
list_for_each_entry(cmd, &table, list)
if (cmd->bdev == bdev) {
atomic_inc(&cmd->ref_count);
return cmd;
}
return NULL;
}
static struct dm_cache_metadata *lookup_or_open(struct block_device *bdev,
sector_t data_block_size,
bool may_format_device,
size_t policy_hint_size)
{
struct dm_cache_metadata *cmd, *cmd2;
mutex_lock(&table_lock);
cmd = lookup(bdev);
mutex_unlock(&table_lock);
if (cmd)
return cmd;
cmd = metadata_open(bdev, data_block_size, may_format_device, policy_hint_size);
if (cmd) {
mutex_lock(&table_lock);
cmd2 = lookup(bdev);
if (cmd2) {
mutex_unlock(&table_lock);
__destroy_persistent_data_objects(cmd);
kfree(cmd);
return cmd2;
}
list_add(&cmd->list, &table);
mutex_unlock(&table_lock);
}
return cmd;
}
static bool same_params(struct dm_cache_metadata *cmd, sector_t data_block_size)
{
if (cmd->data_block_size != data_block_size) {
DMERR("data_block_size (%llu) different from that in metadata (%llu)\n",
(unsigned long long) data_block_size,
(unsigned long long) cmd->data_block_size);
return false;
}
return true;
}
struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
sector_t data_block_size,
bool may_format_device,
size_t policy_hint_size)
{
struct dm_cache_metadata *cmd = lookup_or_open(bdev, data_block_size,
may_format_device, policy_hint_size);
if (cmd && !same_params(cmd, data_block_size)) {
dm_cache_metadata_close(cmd);
return NULL;
}
return cmd;
}
void dm_cache_metadata_close(struct dm_cache_metadata *cmd)
{
__destroy_persistent_data_objects(cmd);
kfree(cmd);
if (atomic_dec_and_test(&cmd->ref_count)) {
mutex_lock(&table_lock);
list_del(&cmd->list);
mutex_unlock(&table_lock);
__destroy_persistent_data_objects(cmd);
kfree(cmd);
}
}
/*