linux.git/drivers/md/raid10.c, branch v3.4-rc2

md/raid1,raid10: don't compare excess byte during consistency check.

2012-04-03T05:39:23+00:00

When comparing two pages read from different legs of a mirror, only
compare the bytes that were read, not the whole page.

In most cases we read a whole page, but in some cases with
bad blocks or odd sizes devices we might read fewer than that.

This bug has been present "forever" but at worst it might cause
a report of two many mismatches and generate a little bit
extra resync IO, so there is no need to back-port to -stable
kernels.

Reported-by: majianpeng 
Signed-off-by: NeilBrown

md/raid10 - support resizing some RAID10 arrays.

2012-03-19T01:46:40+00:00

'resizing' an array in this context means making use of extra
space that has become available in component devices, not adding new
devices.
It also includes shrinking the array to take up less space of
component devices.

This is not supported for array with a 'far' layout.  However
for 'near' and 'offset' layout arrays, adding and removing space at
the end of the devices is easy to support, and this patch provides
that support.

Signed-off-by: NeilBrown

md/raid10: handle merge_bvec_fn in member devices.

2012-03-19T01:46:39+00:00

Currently we don't honour merge_bvec_fn in member devices so if there
is one, we force all requests to be single-page at most.
This is not ideal.

So enhance the raid10 merge_bvec_fn to check that function in children
as well.

This introduces a small problem.  There is no locking around calls
the ->merge_bvec_fn and subsequent calls to ->make_request.  So a
device added between these could end up getting a request which
violates its merge_bvec_fn.

Currently the best we can do is synchronize_sched().  This will work
providing no preemption happens.  If there is preemption, we just
have to hope that new devices are largely consistent with old devices.

Signed-off-by: NeilBrown

md: tidy up rdev_for_each usage.

2012-03-19T01:46:39+00:00

md.h has an 'rdev_for_each()' macro for iterating the rdevs in an
mddev.  However it uses the 'safe' version of list_for_each_entry,
and so requires the extra variable, but doesn't include 'safe' in the
name, which is useful documentation.

Consequently some places use this safe version without needing it, and
many use an explicity list_for_each entry.

So:
 - rename rdev_for_each to rdev_for_each_safe
 - create a new rdev_for_each which uses the plain
   list_for_each_entry,
 - use the 'safe' version only where needed, and convert all other
   list_for_each_entry calls to use rdev_for_each.

Signed-off-by: NeilBrown

md/raid1,raid10: avoid deadlock during resync/recovery.

2012-03-19T01:46:38+00:00

If RAID1 or RAID10 is used under LVM or some other stacking
block device, it is possible to enter a deadlock during
resync or recovery.
This can happen if the upper level block device creates
two requests to the RAID1 or RAID10.  The first request gets
processed, blocks recovery and queue requests for underlying
requests in current->bio_list.  A resync request then starts
which will wait for those requests and block new IO.

But then the second request to the RAID1/10 will be attempted
and it cannot progress until the resync request completes,
which cannot progress until the underlying device requests complete,
which are on a queue behind that second request.

So allow that second request to proceed even though there is
a resync request about to start.

This is suitable for any -stable kernel.

Cc: stable@vger.kernel.org
Reported-by: Ray Morris 
Tested-by: Ray Morris 
Signed-off-by: NeilBrown

md: allow re-add to failed arrays.

2012-03-19T01:46:37+00:00

When an array is failed (some data inaccessible) then there is no
point attempting to add a spare as it could not possibly be recovered.

However that may be value in re-adding a recently removed device.
e.g. if there is a write-intent-bitmap and it is clear, then access
to the data could be restored by this action.

So don't reject a re-add to a failed array for RAID10 and RAID5 (the
only arrays  types that check for a failed array).

Signed-off-by: NeilBrown

md/raid10: remove unnecessary smp_mb() from end_sync_write

2012-03-13T00:21:20+00:00

Recent commit 4ca40c2ce099e4f1ce3 (md/raid10: Allow replacement device ...)
added an smp_mb in end_sync_write.
This was to close a possible race with raid10_remove_disk.
However there is no such race as it is never attempted to remove a
disk while resync (or recovery) is happening.
so the smp_mb is just noise.

Signed-off-by: NeilBrown

md/raid10: fix assembling of arrays with replacement devices.

2012-03-05T23:12:45+00:00

commit 56a2559bb654a (md/raid10: recognise replacements ...)
changed 'run' to set ->replacement or ->rdev depending on the
'Replacement' status if the device, but it didn't remove the
old unconditional setting of 'rdev'.  So it was largely ineffective.

So remove that now.

Signed-off-by: NeilBrown

md/raid10: fix handling of error on last working device in array.

2012-02-14T00:10:10+00:00

If we get a read error on the last working device in a RAID10 which
contains the target block, then we don't fail the device (which is
good) but we don't abort retries, which is wrong.
We end up in an infinite loop retrying the read on the one device.

This patch fixes the problem in two places:
1/ in raid10_end_read_request we don't even ask for a retry if this
   was the last usable device.  This is efficient but a little racy
   and will sometimes retry when it should not.

2/ in handle_read_error we are careful to exclude any device from
   retry which we tried to mark as faulty (that might have failed if
   it was the last device).  This is race-free but less efficient.

Signed-off-by: NeilBrown

md/raid10: If there is a spare and a want_replacement device, start replacement.

2011-12-22T23:17:56+00:00

When attempting to add a spare to a RAID10 array, also consider
adding it as a replacement for a want_replacement device.

Signed-off-by: NeilBrown