Wang,

 There seems to be a problem - after we delete the seed
 disk, the total_devices didn't decrement back to 1.
 reproducer as in the below test case. (I used btrfs-devlist
 (posted) to check fs_devices).

 > # 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
 mount -o rw,remount /mnt
 btrfs dev del /dev/sdb /mnt --> fs_devices->total_devices is still 2

Thanks, Anand


On 13/05/14 17:05, Wang Shilong wrote:
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.f...@cn.fujitsu.com>
---
  fs/btrfs/volumes.c | 1 -
  1 file changed, 1 deletion(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 6fd7fe6..19b2d32 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1883,7 +1883,6 @@ static int btrfs_prepare_sprout(struct btrfs_root *root)
        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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