[PATCH 0/3 v3] flags to access backup SB

[Anand Jain <anand.jain@oracle.com>]

We need a mechanism to tell when to use the backup super_block.
To do this it needs a frame-work, and the patch #1 and #2 below
provides the same without change in the logic. The last patch
uses the framework to fix the bug(s).

v2->v3:
        Accepts David and Eric review, which would result in disabled
          access to backup-superblock by default.
        Dropped the patch
                [PATCH 3/3] btrfs-progs: use BTRFS_SCAN_BACKUP_SB flag in btrfs_scan_one_device
        Introduced a new patch
                [PATCH 3/3] btrfs-progs: disable using backup superblock by default

v1->v2:
        Accepts Eric and Zach review.
        Separates fix into 3 patches for easy logical understanding

Anand Jain (3):
  btrfs-progs: Introduce flag BTRFS_SCAN_REGISTER to replace run_ioctl
  btrfs-progs: Introduce flag BTRFS_SCAN_BACKUP_SB for
    btrfs_read_dev_super
  btrfs-progs: disable using backup superblock by default

 btrfsctl.c    |  2 +-
 cmds-device.c |  4 ++--
 disk-io.c     | 13 +++++++++----
 disk-io.h     |  3 ++-
 find-root.c   |  6 ++++--
 utils.c       | 17 +++++++++--------
 utils.h       |  8 +++++---
 volumes.c     |  4 +++-
 8 files changed, 35 insertions(+), 22 deletions(-)

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1.8.1.227.g44fe835