linux-stable.git/drivers/md/linear.c, branch master

md: rename some drivers/md/ files to have an "md-" prefix

2017-10-17T02:06:36+00:00

Motivated by the desire to illiminate the imprecise nature of
DM-specific patches being unnecessarily sent to both the MD maintainer
and mailing-list.  Which is born out of the fact that DM files also
reside in drivers/md/

Now all MD-specific files in drivers/md/ start with either "raid" or
"md-" and the MAINTAINERS file has been updated accordingly.

Shaohua: don't change module name

Signed-off-by: Mike Snitzer 
Signed-off-by: Shaohua Li

block: replace bi_bdev with a gendisk pointer and partitions index

2017-08-23T18:49:55+00:00

This way we don't need a block_device structure to submit I/O.  The
block_device has different life time rules from the gendisk and
request_queue and is usually only available when the block device node
is open.  Other callers need to explicitly create one (e.g. the lightnvm
passthrough code, or the new nvme multipathing code).

For the actual I/O path all that we need is the gendisk, which exists
once per block device.  But given that the block layer also does
partition remapping we additionally need a partition index, which is
used for said remapping in generic_make_request.

Note that all the block drivers generally want request_queue or
sometimes the gendisk, so this removes a layer of indirection all
over the stack.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

md: fix deadlock between mddev_suspend() and md_write_start()

2017-06-13T17:18:01+00:00

If mddev_suspend() races with md_write_start() we can deadlock
with mddev_suspend() waiting for the request that is currently
in md_write_start() to complete the ->make_request() call,
and md_write_start() waiting for the metadata to be updated
to mark the array as 'dirty'.
As metadata updates done by md_check_recovery() only happen then
the mddev_lock() can be claimed, and as mddev_suspend() is often
called with the lock held, these threads wait indefinitely for each
other.

We fix this by having md_write_start() abort if mddev_suspend()
is happening, and ->make_request() aborts if md_write_start()
aborted.
md_make_request() can detect this abort, decrease the ->active_io
count, and wait for mddev_suspend().

Reported-by: Nix 
Fix: 68866e425be2(MD: no sync IO while suspended)
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown 
Signed-off-by: Shaohua Li

Merge branch 'md-next' into md-linus

2017-05-01T21:09:21+00:00

md/linear: improve bio splitting.

2017-04-11T17:17:55+00:00

linear_make_request() uses fs_bio_set, which is meant for filesystems
to use, and loops, possible allocating  from the same bio set multiple
times.
These behaviors can theoretically cause deadlocks, though as
linear requests are hardly ever split, it is unlikely in practice.

Change to use mddev->bio_set - otherwise unused for linear, and submit
the tail of a split request to generic_make_request() for it to
handle.

Signed-off-by: NeilBrown 
Signed-off-by: Shaohua Li

md: support REQ_OP_WRITE_ZEROES

2017-04-08T17:25:38+00:00

Copy & paste from the REQ_OP_WRITE_SAME code.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Hannes Reinecke 
Signed-off-by: Jens Axboe

Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md

2017-02-24T22:42:19+00:00

Pull md updates from Shaohua Li:
 "Mainly fixes bugs and improves performance:

   - Improve scalability for raid1 from Coly

   - Improve raid5-cache read performance, disk efficiency and IO
     pattern from Song and me

   - Fix a race condition of disk hotplug for linear from Coly

   - A few cleanup patches from Ming and Byungchul

   - Fix a memory leak from Neil

   - Fix WRITE SAME IO failure from me

   - Add doc for raid5-cache from me"

* 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md: (23 commits)
  md/raid1: fix write behind issues introduced by bio_clone_bioset_partial
  md/raid1: handle flush request correctly
  md/linear: shutup lockdep warnning
  md/raid1: fix a use-after-free bug
  RAID1: avoid unnecessary spin locks in I/O barrier code
  RAID1: a new I/O barrier implementation to remove resync window
  md/raid5: Don't reinvent the wheel but use existing llist API
  md: fast clone bio in bio_clone_mddev()
  md: remove unnecessary check on mddev
  md/raid1: use bio_clone_bioset_partial() in case of write behind
  md: fail if mddev->bio_set can't be created
  block: introduce bio_clone_bioset_partial()
  md: disable WRITE SAME if it fails in underlayer disks
  md/raid5-cache: exclude reclaiming stripes in reclaim check
  md/raid5-cache: stripe reclaim only counts valid stripes
  MD: add doc for raid5-cache
  Documentation: move MD related doc into a separate dir
  md: ensure md devices are freed before module is unloaded.
  md/r5cache: improve journal device efficiency
  md/r5cache: enable chunk_aligned_read with write back cache
  ...

md/linear: shutup lockdep warnning

2017-02-23T19:59:42+00:00

Commit 03a9e24(md linear: fix a race between linear_add() and
linear_congested()) introduces the warnning.

Acked-by: Coly Li 
Signed-off-by: Shaohua Li

md: disable WRITE SAME if it fails in underlayer disks

2017-02-14T03:24:16+00:00

This makes md do the same thing as dm for write same IO failure. Please
see 7eee4ae(dm: disable WRITE SAME if it fails) for details why we need
this.

We did a little bit different than dm. Instead of disabling writesame in
the first IO error, we disable it till next writesame IO coming after
the first IO error. This way we don't need to clone a bio.

Also reported here: https://bugzilla.kernel.org/show_bug.cgi?id=118581

Suggested-by: NeilBrown 
Acked-by: NeilBrown 
Signed-off-by: Shaohua Li

md linear: fix a race between linear_add() and linear_congested()

2017-02-13T17:17:50+00:00

Recently I receive a bug report that on Linux v3.0 based kerenl, hot add
disk to a md linear device causes kernel crash at linear_congested(). From
the crash image analysis, I find in linear_congested(), mddev->raid_disks
contains value N, but conf->disks[] only has N-1 pointers available. Then
a NULL pointer deference crashes the kernel.

There is a race between linear_add() and linear_congested(), RCU stuffs
used in these two functions cannot avoid the race. Since Linuv v4.0
RCU code is replaced by introducing mddev_suspend().  After checking the
upstream code, it seems linear_congested() is not called in
generic_make_request() code patch, so mddev_suspend() cannot provent it
from being called. The possible race still exists.

Here I explain how the race still exists in current code.  For a machine
has many CPUs, on one CPU, linear_add() is called to add a hard disk to a
md linear device; at the same time on other CPU, linear_congested() is
called to detect whether this md linear device is congested before issuing
an I/O request onto it.

Now I use a possible code execution time sequence to demo how the possible
race happens,

seq    linear_add()                linear_congested()
 0                                 conf=mddev->private
 1   oldconf=mddev->private
 2   mddev->raid_disks++
 3                              for (i=0; iraid_disks;i++)
 4                                bdev_get_queue(conf->disks[i].rdev->bdev)
 5   mddev->private=newconf

In linear_add() mddev->raid_disks is increased in time seq 2, and on
another CPU in linear_congested() the for-loop iterates conf->disks[i] by
the increased mddev->raid_disks in time seq 3,4. But conf with one more
element (which is a pointer to struct dev_info type) to conf->disks[] is
not updated yet, accessing its structure member in time seq 4 will cause a
NULL pointer deference fault.

To fix this race, there are 2 parts of modification in the patch,
 1) Add 'int raid_disks' in struct linear_conf, as a copy of
    mddev->raid_disks. It is initialized in linear_conf(), always being
    consistent with pointers number of 'struct dev_info disks[]'. When
    iterating conf->disks[] in linear_congested(), use conf->raid_disks to
    replace mddev->raid_disks in the for-loop, then NULL pointer deference
    will not happen again.
 2) RCU stuffs are back again, and use kfree_rcu() in linear_add() to
    free oldconf memory. Because oldconf may be referenced as mddev->private
    in linear_congested(), kfree_rcu() makes sure that its memory will not
    be released until no one uses it any more.
Also some code comments are added in this patch, to make this modification
to be easier understandable.

This patch can be applied for kernels since v4.0 after commit:
3be260cc18f8 ("md/linear: remove rcu protections in favour of
suspend/resume"). But this bug is reported on Linux v3.0 based kernel, for
people who maintain kernels before Linux v4.0, they need to do some back
back port to this patch.

Changelog:
 - V3: add 'int raid_disks' in struct linear_conf, and use kfree_rcu() to
       replace rcu_call() in linear_add().
 - v2: add RCU stuffs by suggestion from Shaohua and Neil.
 - v1: initial effort.

Signed-off-by: Coly Li 
Cc: Shaohua Li 
Cc: Neil Brown 
Cc: stable@vger.kernel.org
Signed-off-by: Shaohua Li