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authorNikos Tsironis <ntsironis@arrikto.com>2019-12-04 16:06:53 +0200
committerMike Snitzer <snitzer@redhat.com>2019-12-05 15:27:54 -0500
commit8fdbfe8d1690e8a38d497d83a30607d0d90cc15a (patch)
tree4e46c590e6dc293b0167b51c063025e3288d6678
parente6a505f3f9fae572fb3ab3bc486e755ac9cef32c (diff)
dm clone metadata: Use a two phase commit
Split the metadata commit in two parts: 1. dm_clone_metadata_pre_commit(): Prepare the current transaction for committing. After this is called, all subsequent metadata updates, done through either dm_clone_set_region_hydrated() or dm_clone_cond_set_range(), will be part of the next transaction. 2. dm_clone_metadata_commit(): Actually commit the current transaction to disk and start a new transaction. This is required by the following commit. It allows dm-clone to flush the destination device after step (1) to ensure that all freshly hydrated regions, for which we are updating the metadata, are properly written to non-volatile storage and won't be lost in case of a crash. Fixes: 7431b7835f55 ("dm: add clone target") Cc: stable@vger.kernel.org # v5.4+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
-rw-r--r--drivers/md/dm-clone-metadata.c46
-rw-r--r--drivers/md/dm-clone-metadata.h17
-rw-r--r--drivers/md/dm-clone-target.c7
3 files changed, 60 insertions, 10 deletions
diff --git a/drivers/md/dm-clone-metadata.c b/drivers/md/dm-clone-metadata.c
index ee870a425ab8..c05b12110456 100644
--- a/drivers/md/dm-clone-metadata.c
+++ b/drivers/md/dm-clone-metadata.c
@@ -127,6 +127,9 @@ struct dm_clone_metadata {
struct dirty_map dmap[2];
struct dirty_map *current_dmap;
+ /* Protected by lock */
+ struct dirty_map *committing_dmap;
+
/*
* In core copy of the on-disk bitmap to save constantly doing look ups
* on disk.
@@ -511,6 +514,7 @@ static int dirty_map_init(struct dm_clone_metadata *cmd)
}
cmd->current_dmap = &cmd->dmap[0];
+ cmd->committing_dmap = NULL;
return 0;
}
@@ -775,15 +779,17 @@ static int __flush_dmap(struct dm_clone_metadata *cmd, struct dirty_map *dmap)
return 0;
}
-int dm_clone_metadata_commit(struct dm_clone_metadata *cmd)
+int dm_clone_metadata_pre_commit(struct dm_clone_metadata *cmd)
{
- int r = -EPERM;
+ int r = 0;
struct dirty_map *dmap, *next_dmap;
down_write(&cmd->lock);
- if (cmd->fail_io || dm_bm_is_read_only(cmd->bm))
+ if (cmd->fail_io || dm_bm_is_read_only(cmd->bm)) {
+ r = -EPERM;
goto out;
+ }
/* Get current dirty bitmap */
dmap = cmd->current_dmap;
@@ -795,7 +801,7 @@ int dm_clone_metadata_commit(struct dm_clone_metadata *cmd)
* The last commit failed, so we don't have a clean dirty-bitmap to
* use.
*/
- if (WARN_ON(next_dmap->changed)) {
+ if (WARN_ON(next_dmap->changed || cmd->committing_dmap)) {
r = -EINVAL;
goto out;
}
@@ -805,11 +811,33 @@ int dm_clone_metadata_commit(struct dm_clone_metadata *cmd)
cmd->current_dmap = next_dmap;
spin_unlock_irq(&cmd->bitmap_lock);
- /*
- * No one is accessing the old dirty bitmap anymore, so we can flush
- * it.
- */
- r = __flush_dmap(cmd, dmap);
+ /* Set old dirty bitmap as currently committing */
+ cmd->committing_dmap = dmap;
+out:
+ up_write(&cmd->lock);
+
+ return r;
+}
+
+int dm_clone_metadata_commit(struct dm_clone_metadata *cmd)
+{
+ int r = -EPERM;
+
+ down_write(&cmd->lock);
+
+ if (cmd->fail_io || dm_bm_is_read_only(cmd->bm))
+ goto out;
+
+ if (WARN_ON(!cmd->committing_dmap)) {
+ r = -EINVAL;
+ goto out;
+ }
+
+ r = __flush_dmap(cmd, cmd->committing_dmap);
+ if (!r) {
+ /* Clear committing dmap */
+ cmd->committing_dmap = NULL;
+ }
out:
up_write(&cmd->lock);
diff --git a/drivers/md/dm-clone-metadata.h b/drivers/md/dm-clone-metadata.h
index 3fe50a781c11..14af1ebd853f 100644
--- a/drivers/md/dm-clone-metadata.h
+++ b/drivers/md/dm-clone-metadata.h
@@ -75,7 +75,23 @@ void dm_clone_metadata_close(struct dm_clone_metadata *cmd);
/*
* Commit dm-clone metadata to disk.
+ *
+ * We use a two phase commit:
+ *
+ * 1. dm_clone_metadata_pre_commit(): Prepare the current transaction for
+ * committing. After this is called, all subsequent metadata updates, done
+ * through either dm_clone_set_region_hydrated() or
+ * dm_clone_cond_set_range(), will be part of the **next** transaction.
+ *
+ * 2. dm_clone_metadata_commit(): Actually commit the current transaction to
+ * disk and start a new transaction.
+ *
+ * This allows dm-clone to flush the destination device after step (1) to
+ * ensure that all freshly hydrated regions, for which we are updating the
+ * metadata, are properly written to non-volatile storage and won't be lost in
+ * case of a crash.
*/
+int dm_clone_metadata_pre_commit(struct dm_clone_metadata *cmd);
int dm_clone_metadata_commit(struct dm_clone_metadata *cmd);
/*
@@ -112,6 +128,7 @@ int dm_clone_metadata_abort(struct dm_clone_metadata *cmd);
* Switches metadata to a read only mode. Once read-only mode has been entered
* the following functions will return -EPERM:
*
+ * dm_clone_metadata_pre_commit()
* dm_clone_metadata_commit()
* dm_clone_set_region_hydrated()
* dm_clone_cond_set_range()
diff --git a/drivers/md/dm-clone-target.c b/drivers/md/dm-clone-target.c
index b3d89072d21c..613c913c296c 100644
--- a/drivers/md/dm-clone-target.c
+++ b/drivers/md/dm-clone-target.c
@@ -1122,8 +1122,13 @@ static int commit_metadata(struct clone *clone)
goto out;
}
- r = dm_clone_metadata_commit(clone->cmd);
+ r = dm_clone_metadata_pre_commit(clone->cmd);
+ if (unlikely(r)) {
+ __metadata_operation_failed(clone, "dm_clone_metadata_pre_commit", r);
+ goto out;
+ }
+ r = dm_clone_metadata_commit(clone->cmd);
if (unlikely(r)) {
__metadata_operation_failed(clone, "dm_clone_metadata_commit", r);
goto out;