From: Nigel Croxon ncroxon@redhat.com

Changing state from check_state_check_result to check_state_compute_result not only is unsafe but also doesn't appear to serve a valid purpose. A raid6 check should only be pushing out extra writes if doing repair and a mis-match occurs. The stripe dev management will already try and do repair writes for failing sectors.

This patch makes the raid6 check_state_check_result handling work more like raid5's. If somehow too many failures for a check, just quit the check operation for the stripe. When any checks pass, don't try and use check_state_compute_result for a purpose it isn't needed for and is unsafe for. Just mark the stripe as in sync for passing its parity checks and let the stripe dev read/write code and the bad blocks list do their job handling I/O errors.

Repro steps from Xiao:

These are the steps to reproduce this problem: 1. redefined OPT_MEDIUM_ERR_ADDR to 12000 in scsi_debug.c 2. insmod scsi_debug.ko dev_size_mb=11000 max_luns=1 num_tgts=1 3. mdadm --create /dev/md127 --level=6 --raid-devices=5 /dev/sde1 /dev/sde2 /dev/sde3 /dev/sde5 /dev/sde6 sde is the disk created by scsi_debug 4. echo "2" >/sys/module/scsi_debug/parameters/opts 5. raid-check

It panic: [ 4854.730899] md: data-check of RAID array md127 [ 4854.857455] sd 5:0:0:0: [sdr] tag#80 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 4854.859246] sd 5:0:0:0: [sdr] tag#80 Sense Key : Medium Error [current] [ 4854.860694] sd 5:0:0:0: [sdr] tag#80 Add. Sense: Unrecovered read error [ 4854.862207] sd 5:0:0:0: [sdr] tag#80 CDB: Read(10) 28 00 00 00 2d 88 00 04 00 00 [ 4854.864196] print_req_error: critical medium error, dev sdr, sector 11656 flags 0 [ 4854.867409] sd 5:0:0:0: [sdr] tag#100 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 4854.869469] sd 5:0:0:0: [sdr] tag#100 Sense Key : Medium Error [current] [ 4854.871206] sd 5:0:0:0: [sdr] tag#100 Add. Sense: Unrecovered read error [ 4854.872858] sd 5:0:0:0: [sdr] tag#100 CDB: Read(10) 28 00 00 00 2e e0 00 00 08 00 [ 4854.874587] print_req_error: critical medium error, dev sdr, sector 12000 flags 4000 [ 4854.876456] sd 5:0:0:0: [sdr] tag#101 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 4854.878552] sd 5:0:0:0: [sdr] tag#101 Sense Key : Medium Error [current] [ 4854.880278] sd 5:0:0:0: [sdr] tag#101 Add. Sense: Unrecovered read error [ 4854.881846] sd 5:0:0:0: [sdr] tag#101 CDB: Read(10) 28 00 00 00 2e e8 00 00 08 00 [ 4854.883691] print_req_error: critical medium error, dev sdr, sector 12008 flags 4000 [ 4854.893927] sd 5:0:0:0: [sdr] tag#166 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 4854.896002] sd 5:0:0:0: [sdr] tag#166 Sense Key : Medium Error [current] [ 4854.897561] sd 5:0:0:0: [sdr] tag#166 Add. Sense: Unrecovered read error [ 4854.899110] sd 5:0:0:0: [sdr] tag#166 CDB: Read(10) 28 00 00 00 2e e0 00 00 10 00 [ 4854.900989] print_req_error: critical medium error, dev sdr, sector 12000 flags 0 [ 4854.902757] md/raid:md127: read error NOT corrected!! (sector 9952 on sdr1). [ 4854.904375] md/raid:md127: read error NOT corrected!! (sector 9960 on sdr1). [ 4854.906201] ------------[ cut here ]------------ [ 4854.907341] kernel BUG at drivers/md/raid5.c:4190!

raid5.c:4190 above is this BUG_ON:

handle_parity_checks6() ... BUG_ON(s->uptodate < disks - 1); /* We don't need Q to recover */

Cc: stable@vger.kernel.org # v3.16+ OriginalAuthor: David Jeffery djeffery@redhat.com Cc: Xiao Ni xni@redhat.com Tested-by: David Jeffery djeffery@redhat.com Signed-off-by: David Jeffy djeffery@redhat.com Signed-off-by: Nigel Croxon ncroxon@redhat.com Signed-off-by: Song Liu songliubraving@fb.com --- drivers/md/raid5.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index c033bfcb209e..4204a972ecf2 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -4223,26 +4223,15 @@ static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh, case check_state_check_result: sh->check_state = check_state_idle;

+ if (s->failed > 1) + break; /* handle a successful check operation, if parity is correct * we are done. Otherwise update the mismatch count and repair * parity if !MD_RECOVERY_CHECK */ if (sh->ops.zero_sum_result == 0) { - /* both parities are correct */ - if (!s->failed) - set_bit(STRIPE_INSYNC, &sh->state); - else { - /* in contrast to the raid5 case we can validate - * parity, but still have a failure to write - * back - */ - sh->check_state = check_state_compute_result; - /* Returning at this point means that we may go - * off and bring p and/or q uptodate again so - * we make sure to check zero_sum_result again - * to verify if p or q need writeback - */ - } + /* Any parity checked was correct */ + set_bit(STRIPE_INSYNC, &sh->state); } else { atomic64_add(STRIPE_SECTORS, &conf->mddev->resync_mismatches); if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery)) {