linux.git/drivers/md, branch v2.6.26-rc7

md: do not compute parity unless it is on a failed drive

2008-06-06T18:29:08+00:00

If a block is computed (rather than read) then a check/repair operation
may be lead to believe that the data on disk is correct, when infact it
isn't.  So only compute blocks for failed devices.

This issue has been around since at least 2.6.12, but has become harder to
hit in recent kernels since most reads bypass the cache.

echo repair > /sys/block/mdN/md/sync_action will set the parity blocks to the
correct state.

Cc: 
Signed-off-by: Dan Williams 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: fix uninitialized use of mddev->recovery_wait

2008-06-06T18:29:08+00:00

If an array was created with --assume-clean we will oops when trying to
set ->resync_max.

Fix this by initializing ->recovery_wait in mddev_find.

Cc: 
Signed-off-by: Dan Williams 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: fix prexor vs sync_request race

2008-06-06T18:29:08+00:00

During the initial array synchronization process there is a window between
when a prexor operation is scheduled to a specific stripe and when it
completes for a sync_request to be scheduled to the same stripe.  When
this happens the prexor completes and the stripe is unconditionally marked
"insync", effectively canceling the sync_request for the stripe.  Prior to
2.6.23 this was not a problem because the prexor operation was done under
sh->lock.  The effect in older kernels being that the prexor would still
erroneously mark the stripe "insync", but sync_request would be held off
and re-mark the stripe as "!in_sync".

Change the write completion logic to not mark the stripe "in_sync" if a
prexor was performed.  The effect of the change is to sometimes not set
STRIPE_INSYNC.  The worst this can do is cause the resync to stall waiting
for STRIPE_INSYNC to be set.  If this were happening, then STRIPE_SYNCING
would be set and handle_issuing_new_read_requests would cause all
available blocks to eventually be read, at which point prexor would never
be used on that stripe any more and STRIPE_INSYNC would eventually be set.

echo repair > /sys/block/mdN/md/sync_action will correct arrays that may
have lost this race.

Cc: 
Signed-off-by: Dan Williams 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: restart recovery cleanly after device failure.

2008-05-24T16:56:10+00:00

When we get any IO error during a recovery (rebuilding a spare), we abort
the recovery and restart it.

For RAID6 (and multi-drive RAID1) it may not be best to restart at the
beginning: when multiple failures can be tolerated, the recovery may be
able to continue and re-doing all that has already been done doesn't make
sense.

We already have the infrastructure to record where a recovery is up to
and restart from there, but it is not being used properly.
This is because:
  - We sometimes abort with MD_RECOVERY_ERR rather than just MD_RECOVERY_INTR,
    which causes the recovery not be be checkpointed.
  - We remove spares and then re-added them which loses important state
    information.

The distinction between MD_RECOVERY_ERR and MD_RECOVERY_INTR really isn't
needed.  If there is an error, the relevant drive will be marked as
Faulty, and that is enough to ensure correct handling of the error.  So we
first remove MD_RECOVERY_ERR, changing some of the uses of it to
MD_RECOVERY_INTR.

Then we cause the attempt to remove a non-faulty device from an array to
fail (unless recovery is impossible as the array is too degraded).  Then
when remove_and_add_spares attempts to remove the devices on which
recovery can continue, it will fail, they will remain in place, and
recovery will continue on them as desired.

Issue:  If we are halfway through rebuilding a spare and another drive
fails, and a new spare is immediately available,  do we want to:
 1/ complete the current rebuild, then go back and rebuild the new spare or
 2/ restart the rebuild from the start and rebuild both devices in
    parallel.

Both options can be argued for.  The code currently takes option 2 as
  a/ this requires least code change
  b/ this results in a minimally-degraded array in minimal time.

Cc: "Eivind Sarto" 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: allow parallel resync of md-devices.

2008-05-24T16:56:10+00:00

In some configurations, a raid6 resync can be limited by CPU speed
(Calculating P and Q and moving data) rather than by device speed.  In
these cases there is nothing to be gained byt serialising resync of arrays
that share a device, and doing the resync in parallel can provide benefit.
 So add a sysfs tunable to flag an array as being allowed to resync in
parallel with other arrays that use (a different part of) the same device.

Signed-off-by: Bernd Schubert 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: notify userspace on 'stop' events

2008-05-24T16:56:10+00:00

This additional notification to 'array_state' is needed to allow the
monitor application to learn about stop events via sysfs.  The
sysfs_notify("sync_action") call that comes at the end of do_md_stop()
(via md_new_event) is insufficient since the 'sync_action' attribute has
been removed by this point.

(Seems like a sysfs-notify-on-removal patch is a better fix.  Currently
removal updates the event count but does not wake up waiters)

Signed-off-by: Dan Williams 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: notify userspace on 'write-pending' changes to array_state

2008-05-24T16:56:10+00:00

When an array enters write pending, 'array_state' changes, so we must be
sure to sysfs_notify.

Also, when waiting for user-space to acknowledge 'write-pending' by
marking the metadata as dirty, we don't want to wait for MD_CHANGE_DEVS to
be cleared as that might not happen.  So explicity test for the bits that
we are really interested in.

Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: raid1: Fix restoration of bio between failed read and write.

2008-05-24T16:56:10+00:00

When performing a "recovery" or "check" pass on a RAID1 array, we read
from each device and possible, if there is a difference or a read error,
write back to some devices.

We use the same 'bio' for both read and write, resetting various fields
between the two operations.

We forgot to reset bv_offset and bv_len however.  These are often left
unchanged, but in the case where there is an IO error one or two sectors
into a page, they are changed.

This results in correctable errors not being corrected properly.  It does
not result in any data corruption.

Cc: "Fairbanks, David" 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: md: raid5 rate limit error printk

2008-05-24T16:56:10+00:00

Last night we had scsi problems and a hardware raid unit was offlined
during heavy i/o.  While this happened we got for about 3 minutes a huge
number messages like these

Apr 12 03:36:07 pfs1n14 kernel: [197510.696595] raid5:md7: read error not correctable (sector 2993096568 on sdj2).

I guess the high error rate is responsible for not scheduling other events
- during this time the system was not pingable and in the end also other
devices run into scsi command timeouts causing problems on these unrelated
devices as well.

Signed-off-by: Bernd Schubert 
Signed-off-by: Dan Williams 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: kill file_path wrapper

2008-05-24T16:56:09+00:00

Kill the trivial and rather pointless file_path wrapper around d_path.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Neil Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds