[PATCH 3.12 092/118] dm thin: allow pool in read-only mode to transition to read-write mode

Greg Kroah-Hartman
2013-12-18T21:24:37Z

From: Joe Thornber <ejt@redhat.com>

commit 9b7aaa64f96f7ca280d75326fca42f42017b89ef upstream.

A thin-pool may be in read-only mode because the pool's data or metadata
space was exhausted. To allow for recovery, by adding more space to the
pool, we must allow a pool to transition from PM_READ_ONLY to PM_WRITE
mode. Otherwise, running out of space will render the pool permanently
read-only.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-thin-metadata.c | 8 ++++++++
drivers/md/dm-thin-metadata.h | 1 +
drivers/md/dm-thin.c | 12 ++++++++++--
drivers/md/persistent-data/dm-block-manager.c | 6 ++++++
drivers/md/persistent-data/dm-block-manager.h | 7 ++++---
5 files changed, 29 insertions(+), 5 deletions(-)

--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1697,6 +1697,14 @@ void dm_pool_metadata_read_only(struct d
up_write(&pmd->root_lock);
}

+void dm_pool_metadata_read_write(struct dm_pool_metadata *pmd)
+{
+ down_write(&pmd->root_lock);
+ pmd->read_only = false;
+ dm_bm_set_read_write(pmd->bm);
+ up_write(&pmd->root_lock);
+}
+
int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
dm_block_t threshold,
dm_sm_threshold_fn fn,
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -193,6 +193,7 @@ int dm_pool_resize_metadata_dev(struct d
* that nothing is changing.
*/
void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd);
+void dm_pool_metadata_read_write(struct dm_pool_metadata *pmd);

int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
dm_block_t threshold,
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1425,6 +1425,7 @@ static void set_pool_mode(struct pool *p
break;

case PM_WRITE:
+ dm_pool_metadata_read_write(pool->pmd);
pool->process_bio = process_bio;
pool->process_discard = process_discard;
pool->process_prepared_mapping = process_prepared_mapping;
@@ -1641,12 +1642,19 @@ static int bind_control_target(struct po
struct pool_c *pt = ti->private;

/*
- * We want to make sure that degraded pools are never upgraded.
+ * We want to make sure that a pool in PM_FAIL mode is never upgraded.
*/
enum pool_mode old_mode = pool->pf.mode;
enum pool_mode new_mode = pt->adjusted_pf.mode;

- if (old_mode > new_mode)
+ /*
+ * If we were in PM_FAIL mode, rollback of metadata failed. We're
+ * not going to recover without a thin_repair. So we never let the
+ * pool move out of the old mode. On the other hand a PM_READ_ONLY
+ * may have been due to a lack of metadata or data space, and may
+ * now work (ie. if the underlying devices have been resized).
+ */
+ if (old_mode == PM_FAIL)
new_mode = old_mode;

pool->ti = ti;
--- a/drivers/md/persistent-data/dm-block-manager.c
+++ b/drivers/md/persistent-data/dm-block-manager.c
@@ -626,6 +626,12 @@ void dm_bm_set_read_only(struct dm_block
}
EXPORT_SYMBOL_GPL(dm_bm_set_read_only);

+void dm_bm_set_read_write(struct dm_block_manager *bm)
+{
+ bm->read_only = false;
+}
+EXPORT_SYMBOL_GPL(dm_bm_set_read_write);
+
u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor)
{
return crc32c(~(u32) 0, data, len) ^ init_xor;
--- a/drivers/md/persistent-data/dm-block-manager.h
+++ b/drivers/md/persistent-data/dm-block-manager.h
@@ -108,9 +108,9 @@ int dm_bm_unlock(struct dm_block *b);
int dm_bm_flush_and_unlock(struct dm_block_manager *bm,
struct dm_block *superblock);

- /*
- * Request data be prefetched into the cache.
- */
+/*
+ * Request data is prefetched into the cache.
+ */
void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b);

/*
@@ -125,6 +125,7 @@ void dm_bm_prefetch(struct dm_block_mana
* be returned if you do.
*/
void dm_bm_set_read_only(struct dm_block_manager *bm);
+void dm_bm_set_read_write(struct dm_block_manager *bm);

u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);