3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: Mike Snitzer snitzer@redhat.com
commit fd2fa95416188a767a63979296fa3e169a9ef5ec upstream.
policy_hint_size starts as 0 during __write_initial_superblock(). It isn't until the policy is loaded that policy_hint_size is set in-core (cmd->policy_hint_size). But it never got recorded in the on-disk superblock because __commit_transaction() didn't deal with transfering the in-core cmd->policy_hint_size to the on-disk superblock.
The in-core cmd->policy_hint_size gets initialized by metadata_open()'s __begin_transaction_flags() which re-reads all superblock fields. Because the superblock's policy_hint_size was never properly stored, when the cache was created, hints_array_available() would always return false when re-activating a previously created cache. This means __load_mappings() always considered the hints invalid and never made use of the hints (these hints served to optimize).
Another detremental side-effect of this oversight is the cache_check utility would fail with: "invalid hint width: 0"
Signed-off-by: Mike Snitzer snitzer@redhat.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/md/dm-cache-metadata.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/md/dm-cache-metadata.c +++ b/drivers/md/dm-cache-metadata.c @@ -324,7 +324,7 @@ static int __write_initial_superblock(st disk_super->version = cpu_to_le32(MAX_CACHE_VERSION); memset(disk_super->policy_name, 0, sizeof(disk_super->policy_name)); memset(disk_super->policy_version, 0, sizeof(disk_super->policy_version)); - disk_super->policy_hint_size = 0; + disk_super->policy_hint_size = cpu_to_le32(0);
__copy_sm_root(cmd, disk_super);
@@ -635,6 +635,7 @@ static int __commit_transaction(struct d disk_super->policy_version[0] = cpu_to_le32(cmd->policy_version[0]); disk_super->policy_version[1] = cpu_to_le32(cmd->policy_version[1]); disk_super->policy_version[2] = cpu_to_le32(cmd->policy_version[2]); + disk_super->policy_hint_size = cpu_to_le32(cmd->policy_hint_size);
disk_super->read_hits = cpu_to_le32(cmd->stats.read_hits); disk_super->read_misses = cpu_to_le32(cmd->stats.read_misses);