md looping on recovery of raid1 array

[Bin Guo <bguo@starentnetworks.com>]

Hi,

  I had similar errors to the problem reported in

http://marc.info/?l=linux-raid&m=118385063014256&w=2

Using manually coded patch similar to scsi fault injection
tests, I can reproduce the problem:

  1. create degraded raid1 with only disk "sda1"
  2. inject permanent I/O error on a block on "sda1"
  3. try to add spare disk "sdb1" to the raid

Now raid code would loop to sync:

[  295.837203] sd 0:0:0:0: SCSI error: return code = 0x08000002
[  295.842869] sda: Current: sense key=0x3
[  295.846725]     ASC=0x11 ASCQ=0x4
[  295.850081] Info fld=0x1e240
[  295.852958] end_request: I/O error, dev sda, sector 123456
[  295.858454] raid1: sda: unrecoverable I/O read error for block 123136
[  295.864986] md: md0: sync done.
[  295.903715] RAID1 conf printout:
[  295.906939]  --- wd:1 rd:2
[  295.909649]  disk 0, wo:0, o:1, dev:sda1
[  295.913573]  disk 1, wo:1, o:1, dev:sdb1
[  295.920686] RAID1 conf printout:
[  295.923914]  --- wd:1 rd:2
[  295.926634]  disk 0, wo:0, o:1, dev:sda1
[  295.930570] RAID1 conf printout:
[  295.933815]  --- wd:1 rd:2
[  295.936518]  disk 0, wo:0, o:1, dev:sda1
[  295.940442]  disk 1, wo:1, o:1, dev:sdb1
[  295.944419] md: syncing RAID array md0
[  295.948199] md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
[  295.955262] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
[  295.965369] md: using 128k window, over a total of 71289063 blocks.

It seems to be caused by raid1.c:error() doing nothing in this fatal error
case:

       /*
         * If it is not operational, then we have already marked it as dead
         * else if it is the last working disks, ignore the error, let the
         * next level up know.
         * else mark the drive as failed
         */
        if (test_bit(In_sync, &rdev->flags)
            && conf->working_disks == 1)
                /*
                 * Don't fail the drive, act as though we were just a
                 * normal single drive
                 */
                return;

Where is the code in "next level up" handling this? I'm using ancient 2.6.18,
can someone test whether this is the case for newer kernel?

I tested by commenting out those lines, but ends up with a raid1 consisting
of "sdb1" instead of total failure.

-- 
Bin