Re: [PATCH] btrfs-progs: make btrfs dev scan multi path aware

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

On 04/08/2013 11:22 PM, David Sterba wrote:
> On Thu, Mar 21, 2013 at 07:56:44PM +0800, Anand Jain wrote:
>>   We should avoid using non multi-path (mp) path for mp disks
>>   As of now there is no good way (like api) to check that.
>>   A workaround way is to check if the O_EXCL open is unsuccessful.
>>   This is safe since otherwise the BTRFS_IOC_SCAN_DEV ioctl would
>>   fail if the disk-path can not be opened with the flag O_EXCL set.
>
> Agreed. Alternatively we could try to parse the /sys entries.

  sorry to confuse you on this David. hope the below
  description will clarify..

  this patch actually combined two fixes - one as in the
  subject here, and the other a small fix which is to check if
  the kernel module is loaded.

  the later revised patch separated this into two patch-set
    - v6: access to backup superblock (dt: 04/05/13)
    - [PATCH 0/9] a bunch of miscellaneous bug fixes (dt: 04/05/13)

  in the above v6... as indicated I have dropped the
   [PATCH] btrfs-progs: make btrfs dev scan multi path aware
  since its found that when btrfs is mounted it would open
  the dev with O_EXCL as well, so we can't depend on this
  workaround.

  Further original problem related to the multi-path wasn't
  reproducible with my above two patch-sets applied (in the
  same order) on top integration-20130321 . IMO I lost the
  trigger as I don't think there is any fix related to
  multi path. If there is any good reproducible test-case
  related to multi-path I would dig further.

  The above patch set viz. "v6: access to backup superblock"
  and "[PATCH 0/9] a bunch of miscellaneous bug fixes" are
  important. They bring a lot of stability around the area
  of mkfs, btrfs fi show, btrfs dev scan.

Thanks, Anand