linux-kernel - [PATCH 3.15 123/139] Btrfs: set right total device count for seeding support

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Message-Id: <20140628174611.018351343@linuxfoundation.org>
Date:	Sat, 28 Jun 2014 10:48:04 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Wang Shilong <wangsl.fnst@...fujitsu.com>,
	Chris Mason <clm@...com>
Subject: [PATCH 3.15 123/139] Btrfs: set right total device count for seeding support

3.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Wang Shilong <wangsl.fnst@...fujitsu.com>

commit 298658414a2f0bea1f05a81876a45c1cd96aa2e0 upstream.

Seeding device support allows us to create a new filesystem
based on existed filesystem.

However newly created filesystem's @total_devices should include seed
devices. This patch fix the following problem:

 # mkfs.btrfs -f /dev/sdb
 # btrfstune -S 1 /dev/sdb
 # mount /dev/sdb /mnt
 # btrfs device add -f /dev/sdc /mnt --->fs_devices->total_devices = 1
 # umount /mnt
 # mount /dev/sdc /mnt               --->fs_devices->total_devices = 2

This is because we record right @total_devices in superblock, but
@fs_devices->total_devices is reset to be 0 in btrfs_prepare_sprout().

Fix this problem by not resetting @fs_devices->total_devices.

Signed-off-by: Wang Shilong <wangsl.fnst@...fujitsu.com>
Signed-off-by: Chris Mason <clm@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/volumes.c |    1 -
 1 file changed, 1 deletion(-)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1903,7 +1903,6 @@ static int btrfs_prepare_sprout(struct b
 	fs_devices->seeding = 0;
 	fs_devices->num_devices = 0;
 	fs_devices->open_devices = 0;
-	fs_devices->total_devices = 0;
 	fs_devices->seed = seed_devices;
 
 	generate_random_uuid(fs_devices->fsid);


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