Patch "btrfs: fix resending received snapshot with parent" has been added to the 4.3-stable tree

This is a note to let you know that I've just added the patch titled

btrfs: fix resending received snapshot with parent

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
btrfs-fix-resending-received-snapshot-with-parent.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Robin Ruede <[email protected]>
Date: Wed, 30 Sep 2015 21:23:33 +0200
Subject: btrfs: fix resending received snapshot with parent

From: Robin Ruede <[email protected]>

commit b96b1db039ebc584d03a9933b279e0d3e704c528 upstream.

This fixes a regression introduced by 37b8d27d between v4.1 and v4.2.

When a snapshot is received, its received_uuid is set to the original uuid of the subvolume. When that snapshot is then resent to a third filesystem, it's received_uuid is set to the second uuid instead of the original one. The same was true for the parent_uuid. This behaviour was partially changed in 37b8d27d, but in that patch only the parent_uuid was taken from the real original,
not the uuid itself, causing the search for the parent to fail in the case below.

This happens for example when trying to send a series of linked snapshots (e.g. created by snapper) from the backup file system back to the original one.

The following commands reproduce the issue in v4.2.1 (no error in 4.1.6)

    # setup three test file systems
    for i in 1 2 3; do
	    truncate -s 50M fs$i
	    mkfs.btrfs fs$i
	    mkdir $i
	    mount fs$i $i
    done
    echo "content" > 1/testfile
    btrfs su snapshot -r 1/ 1/snap1
    echo "changed content" > 1/testfile
    btrfs su snapshot -r 1/ 1/snap2

    # works fine:
    btrfs send 1/snap1 | btrfs receive 2/
    btrfs send -p 1/snap1 1/snap2 | btrfs receive 2/

# ERROR: could not find parent subvolume btrfs send 2/snap1 | btrfs receive 3/ btrfs send -p 2/snap1 2/snap2 | btrfs receive 3/

---
 fs/btrfs/send.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

@@ -2353,8 +2353,14 @@ static int send_subvol_begin(struct send
 	}
 
 	TLV_PUT_STRING(sctx, BTRFS_SEND_A_PATH, name, namelen);
-	TLV_PUT_UUID(sctx, BTRFS_SEND_A_UUID,
-			sctx->send_root->root_item.uuid);
+
+	if (!btrfs_is_empty_uuid(sctx->send_root->root_item.received_uuid))
+		TLV_PUT_UUID(sctx, BTRFS_SEND_A_UUID,
+			    sctx->send_root->root_item.received_uuid);
+	else
+		TLV_PUT_UUID(sctx, BTRFS_SEND_A_UUID,
+			    sctx->send_root->root_item.uuid);
+
 	TLV_PUT_U64(sctx, BTRFS_SEND_A_CTRANSID,
 		    le64_to_cpu(sctx->send_root->root_item.ctransid));
 	if (parent_root) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/btrfs-fix-resending-received-snapshot-with-parent.patch