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[3.11.y.z,extended,stable] Patch "dm space map metadata: fix bug in resizing of thin metadata" has been added to staging queue

Message ID 1391606089-308-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Feb. 5, 2014, 1:14 p.m. UTC
This is a note to let you know that I have just added a patch titled

    dm space map metadata: fix bug in resizing of thin metadata

to the linux-3.11.y-queue branch of the 3.11.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-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

From a3ab8b2eccc3d3352454371a4e8edc69300bf118 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Tue, 21 Jan 2014 11:07:32 +0000
Subject: dm space map metadata: fix bug in resizing of thin metadata

commit fca028438fb903852beaf7c3fe1cd326651af57d upstream.

This bug was introduced in commit 7e664b3dec431e ("dm space map metadata:
fix extending the space map").

When extending a dm-thin metadata volume we:

- Switch the space map into a simple bootstrap mode, which allocates
  all space linearly from the newly added space.
- Add new bitmap entries for the new space
- Increment the reference counts for those newly allocated bitmap
  entries
- Commit changes to disk
- Switch back out of bootstrap mode.

But, the disk commit may allocate space itself, if so this fact will be
lost when switching out of bootstrap mode.

The bug exhibited itself as an error when the bitmap_root, with an
erroneous ref count of 0, was subsequently decremented as part of a
later disk commit.  This would cause the disk commit to fail, and thinp
to enter read_only mode.  The metadata was not damaged (thin_check
passed).

The fix is to put the increments + commit into a loop, running until
the commit has not allocated extra space.  In practise this loop only
runs twice.

With this fix the following device mapper testsuite test passes:
 dmtest run --suite thin-provisioning -n thin_remove_works_after_resize

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 drivers/md/persistent-data/dm-space-map-metadata.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

--
1.8.3.2
diff mbox

Patch

diff --git a/drivers/md/persistent-data/dm-space-map-metadata.c b/drivers/md/persistent-data/dm-space-map-metadata.c
index f04d92f..afb419e 100644
--- a/drivers/md/persistent-data/dm-space-map-metadata.c
+++ b/drivers/md/persistent-data/dm-space-map-metadata.c
@@ -617,13 +617,23 @@  static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
 	if (r)
 		goto out;

-	for (i = old_len; !r && i < smm->begin; i++) {
-		r = sm_ll_inc(&smm->ll, i, &ev);
+	/*
+	 * We repeatedly increment then commit until the commit doesn't
+	 * allocate any new blocks.
+	 */
+	do {
+		for (i = old_len; !r && i < smm->begin; i++) {
+			r = sm_ll_inc(&smm->ll, i, &ev);
+			if (r)
+				goto out;
+		}
+		old_len = smm->begin;
+
+		r = sm_ll_commit(&smm->ll);
 		if (r)
 			goto out;
-	}

-	r = sm_metadata_commit(sm);
+	} while (old_len != smm->begin);

 out:
 	/*