[PATCH 3.15 096/109] dm thin metadata: do not allow the data block size to change

Greg Kroah-Hartman
2014-07-26T19:02:58Z

From: Mike Snitzer <snitzer@redhat.com>

commit 9aec8629ec829fc9403788cd959e05dd87988bd1 upstream.

The block size for the thin-pool's data device must remained fixed for
the life of the thin-pool. Disallow any attempt to change the
thin-pool's data block size.

It should be noted that attempting to change the data block size via
thin-pool table reload will be ignored as a side-effect of the thin-pool
handover that the thin-pool target does during thin-pool table reload.

Here is an example outcome of attempting to load a thin-pool table that
reduced the thin-pool's data block size from 1024K to 512K.

Before:
kernel: device-mapper: thin: 253:4: growing the data device from 204800 to 409600 blocks

After:
kernel: device-mapper: thin metadata: changing the data block size (from 2048 to 1024) is not supported
kernel: device-mapper: table: 253:4: thin-pool: Error creating metadata object
kernel: device-mapper: ioctl: error adding target to table

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-metadata.c | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -613,6 +613,15 @@ static int __open_metadata(struct dm_poo

disk_super = dm_block_data(sblock);

+ /* Verify the data block size hasn't changed */
+ if (le32_to_cpu(disk_super->data_block_size) != pmd->data_block_size) {
+ DMERR("changing the data block size (from %u to %llu) is not supported",
+ le32_to_cpu(disk_super->data_block_size),
+ (unsigned long long)pmd->data_block_size);
+ r = -EINVAL;
+ goto bad_unlock_sblock;
+ }
+
r = __check_incompat_features(disk_super, pmd);
if (r < 0)
goto bad_unlock_sblock;