[3.13.y.z extended stable] Patch "dm thin metadata: do not allow the data block size to change" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    dm thin metadata: do not allow the data block size to change

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From ca6ecaa4d0c7f5778542df4a19d2a236212efd66 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer at redhat.com>
Date: Mon, 14 Jul 2014 16:35:54 -0400
Subject: dm thin metadata: do not allow the data block size to change

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 at redhat.com>
Acked-by: Joe Thornber <ejt at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/md/dm-thin-metadata.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 07a6ea3..b63095c 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -613,6 +613,15 @@ static int __open_metadata(struct dm_pool_metadata *pmd)

 	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;
--
1.9.1