This reverts commit 7eb418851f3278de67126ea0c427641ab4792c57.

This commit is poorly justified, I can find not discusison in email,
and it clearly causes a problem.

If a device which is being recovered fails and is subsequently
re-added to an array, there could easily have been changes to the
array *before* the point where the recovery was up to.  So the
recovery must start again from the beginning.

If a spare is being recovered and fails, then when it is re-added we
really should do a bitmap-based recovery up to the recovery-offset,
and then a full recovery from there.  Before this reversion, we only
did the "full recovery from there" which is not corect.  After this
reversion with will do a full recovery from the start, which is safer
but not ideal.

It will be left to a future patch to arrange the two different styles
of recovery.

Reported-and-tested-by: Nate Dailey <nate.dailey@stratus.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Cc: stable@vger.kernel.org (3.14+)
Fixes: 7eb418851f32 ("md: allow a partially recovered device to be hot-added to an array.")

If faulty disks of an array are more than allowed degraded number, the
array enters error handling. It will be marked as read-only with
MD_CHANGE_PENDING/RECOVERY_NEEDED set. But currently recovery doesn't
clear CHANGE_PENDING bit for read-only array.  If MD_CHANGE_PENDING is
set for a raid5 array, all returned IO will be hold on a list till the
bit is clear. But recovery nevery clears this bit, the IO is always in
pending state and nevery finish. This has bad effects like upper layer
can't get an IO error and the array can't be stopped.

Fixes: c3cce6cda162 ("md/raid5: ensure device failure recorded before write request returns.")
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>

If a superblock update is pending, wait for it to complete before
letting md_set_readonly() switch to readonly.
Otherwise we might lose important information about a device having
failed.

For external arrays, waiting for superblock updates can wait on
user-space, so in that case, just return an error.

Reported-and-tested-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>

There were a few conflicts that are fairly easy to resolve.

Signed-off-by: NeilBrown <neilb@suse.com>

Pull core block updates from Jens Axboe:
 "This first core part of the block IO changes contains:

   - Cleanup of the bio IO error signaling from Christoph.  We used to
     rely on the uptodate bit and passing around of an error, now we
     store the error in the bio itself.

   - Improvement of the above from myself, by shrinking the bio size
     down again to fit in two cachelines on x86-64.

   - Revert of the max_hw_sectors cap removal from a revision again,
     from Jeff Moyer.  This caused performance regressions in various
     tests.  Reinstate the limit, bump it to a more reasonable size
     instead.

   - Make /sys/block/<dev>/queue/discard_max_bytes writeable, by me.
     Most devices have huge trim limits, which can cause nasty latencies
     when deleting files.  Enable the admin to configure the size down.
     We will look into having a more sane default instead of UINT_MAX
     sectors.

   - Improvement of the SGP gaps logic from Keith Busch.

   - Enable the block core to handle arbitrarily sized bios, which
     enables a nice simplification of bio_add_page() (which is an IO hot
     path).  From Kent.

   - Improvements to the partition io stats accounting, making it
     faster.  From Ming Lei.

   - Also from Ming Lei, a basic fixup for overflow of the sysfs pending
     file in blk-mq, as well as a fix for a blk-mq timeout race
     condition.

   - Ming Lin has been carrying Kents above mentioned patches forward
     for a while, and testing them.  Ming also did a few fixes around
     that.

   - Sasha Levin found and fixed a use-after-free problem introduced by
     the bio->bi_error changes from Christoph.

   - Small blk cgroup cleanup from Viresh Kumar"

* 'for-4.3/core' of git://git.kernel.dk/linux-block: (26 commits)
  blk: Fix bio_io_vec index when checking bvec gaps
  block: Replace SG_GAPS with new queue limits mask
  block: bump BLK_DEF_MAX_SECTORS to 2560
  Revert "block: remove artifical max_hw_sectors cap"
  blk-mq: fix race between timeout and freeing request
  blk-mq: fix buffer overflow when reading sysfs file of 'pending'
  Documentation: update notes in biovecs about arbitrarily sized bios
  block: remove bio_get_nr_vecs()
  fs: use helper bio_add_page() instead of open coding on bi_io_vec
  block: kill merge_bvec_fn() completely
  md/raid5: get rid of bio_fits_rdev()
  md/raid5: split bio for chunk_aligned_read
  block: remove split code in blkdev_issue_{discard,write_same}
  btrfs: remove bio splitting and merge_bvec_fn() calls
  bcache: remove driver private bio splitting code
  block: simplify bio_add_page()
  block: make generic_make_request handle arbitrarily sized bios
  blk-cgroup: Drop unlikely before IS_ERR(_OR_NULL)
  block: don't access bio->bi_error after bio_put()
  block: shrink struct bio down to 2 cache lines again
  ...

When a write to one of the legs of a RAID1 fails, the failure is
recorded in the metadata of the other leg(s) so that after a restart
the data on the failed drive wont be trusted even if that drive seems
to be working again  (maybe a cable was unplugged).

Similarly when we record a bad-block in response to a write failure,
we must not let the write complete until the bad-block update is safe.

Currently there is no interlock between the write request completing
and the metadata update.  So it is possible that the write will
complete, the app will confirm success in some way, and then the
machine will crash before the metadata update completes.

This is an extremely small hole for a racy to fit in, but it is
theoretically possible and so should be closed.

So:
 - set MD_CHANGE_PENDING when requesting a metadata update for a
   failed device, so we can know with certainty when it completes
 - queue requests that experienced an error on a new queue which
   is only processed after the metadata update completes
 - call raid_end_bio_io() on bios in that queue when the time comes.

Signed-off-by: NeilBrown <neilb@suse.com>

This code looks racy.

The only possible race is if two modules try to register at the same
time and that won't happen.  But make the code look safe anyway.

Signed-off-by: NeilBrown <neilb@suse.com>

When node A stops an array while the array is doing a resync, we need
to let another node B take over the resync task.

To achieve the goal, we need the A send an explicit BITMAP_NEEDS_SYNC
message to the cluster. And the node B which received that message will
invoke __recover_slot to do resync.

Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>

We used to set up the safemode_timer timer in md_run. If md_run
would fail before the timer was set up we'd end up trying to modify
a timer that doesn't have a callback function when we access safe_delay_store,
which would trigger a BUG.

neilb: delete init_timer() call as setup_timer() does that.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: NeilBrown <neilb@suse.com>

There can be a small window between the moment that recovery
actually writes the last block and the time when various sysfs
and /proc/mdstat attributes report that it has finished.
During this time, 'sync_completed' can have the wrong value.
This can confuse monitoring software.

So:
 - don't set curr_resync_completed beyond the end of the devices,
 - set it correctly when resync/recovery has completed.

Signed-off-by: NeilBrown <neilb@suse.com>