[PATCH 3.12 089/118] dm thin: switch to read-only mode if metadata space is exhausted

Greg Kroah-Hartman
2013-12-18T21:15:52Z

From: Mike Snitzer <snitzer@redhat.com>

commit 4a02b34e0cf1d0d0dd3737702841da4bf615a50a upstream.

Switch the thin pool to read-only mode in alloc_data_block() if
dm_pool_alloc_data_block() fails because the pool's metadata space is
exhausted.

Differentiate between data and metadata space in messages about no
free space available.

This issue was noticed with the device-mapper-test-suite using:
dmtest run --suite thin-provisioning -n /exhausting_metadata_space_causes_fail_mode/

The quantity of errors logged in this case must be reduced.

before patch:

device-mapper: thin: 253:4: reached low water mark for metadata device: sending event.
device-mapper: space map metadata: unable to allocate new metadata block
device-mapper: space map common: dm_tm_shadow_block() failed
device-mapper: space map metadata: unable to allocate new metadata block
device-mapper: space map common: dm_tm_shadow_block() failed
device-mapper: space map metadata: unable to allocate new metadata block
device-mapper: space map common: dm_tm_shadow_block() failed
device-mapper: space map metadata: unable to allocate new metadata block
device-mapper: space map common: dm_tm_shadow_block() failed
device-mapper: space map metadata: unable to allocate new metadata block
device-mapper: space map common: dm_tm_shadow_block() failed
<snip ... these repeat for a _very_ long while ... >
device-mapper: space map metadata: unable to allocate new metadata block
device-mapper: thin: 253:4: commit failed: error = -28
device-mapper: thin: 253:4: switching pool to read-only mode

after patch:

device-mapper: thin: 253:4: reached low water mark for metadata device: sending event.
device-mapper: space map metadata: unable to allocate new metadata block
device-mapper: thin: 253:4: no free metadata space available.
device-mapper: thin: 253:4: switching pool to read-only mode

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

---
drivers/md/dm-thin.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -959,7 +959,7 @@ static int alloc_data_block(struct thin_
* table reload).
*/
if (!free_blocks) {
- DMWARN("%s: no free space available.",
+ DMWARN("%s: no free data space available.",
dm_device_name(pool->pool_md));
spin_lock_irqsave(&pool->lock, flags);
pool->no_free_space = 1;
@@ -969,8 +969,16 @@ static int alloc_data_block(struct thin_
}

r = dm_pool_alloc_data_block(pool->pmd, result);
- if (r)
+ if (r) {
+ if (r == -ENOSPC &&
+ !dm_pool_get_free_metadata_block_count(pool->pmd, &free_blocks) &&
+ !free_blocks) {
+ DMWARN("%s: no free metadata space available.",
+ dm_device_name(pool->pool_md));
+ set_pool_mode(pool, PM_READ_ONLY);
+ }
return r;
+ }

return 0;
}