Hi,

On 09/10/2012 08:38 AM, Wang Sheng-Hui wrote:
To check the duplicated super blocks, use BTRFS_SUPER_MIRROR_MAX
as the loops limit.

Signed-off-by: Wang Sheng-Hui<[email protected]>
---
  fs/btrfs/disk-io.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 22e98e0..a431144 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2723,7 +2723,7 @@ struct buffer_head *btrfs_read_dev_super(struct 
block_device *bdev)
         * So, we need to add a special mount option to scan for
         * later supers, using BTRFS_SUPER_MIRROR_MAX instead
         */
-       for (i = 0; i<  1; i++) {
+       for (i = 0; i<  BTRFS_SUPER_MIRROR_MAX; i++) {
                bytenr = btrfs_sb_offset(i);
                if (bytenr + 4096>= i_size_read(bdev->bd_inode))
                        break;


Pay attention that when a device is removed from a filesystem by the command "btrfs device delete", *only* the 1st superblock btrfs signature is zeroed [1]. This means that the other (backup) superblocks will be considered valid with your change.



[1] See the function btrfs_rm_device() in volume.c




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