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  1. 08 3月, 2017 4 次提交
  3. 02 3月, 2017 8 次提交
  5. 01 3月, 2017 3 次提交
    • M
      dm raid: bump the target version · 2664f3c9
      由 Mike Snitzer 提交于 
      This version bump reflects that the reshape corruption fix (commit
92a39f6cc "dm raid: fix data corruption on reshape request") is
present.

Done as a separate fix because the above referenced commit is marked for
stable and target version bumps in a stable@ fix are a recipe for the
fix to never get backported to stable@ kernels (because of target
version number conflicts).

Also, move RESUME_STAY_FROZEN_FLAGS up with the reset the the _FLAGS
definitions now that we don't need to worry about stable@ conflicts as a
result of missing context.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
      2664f3c9
    • H
      dm raid: fix data corruption on reshape request · d36a1954
      由 Heinz Mauelshagen 提交于 
      The lvm2 sequence to manage dm-raid constructor flags that trigger a
rebuild or a reshape is defined as:

1) load table with flags (e.g. rebuild/delta_disks/data_offset)
2) clear out the flags in lvm2 metadata
3) store the lvm2 metadata, reload the table to reset the flags
   previously established during the initial load (1) -- in order to
   prevent repeatedly requesting a rebuild or a reshape on activation

Currently, loading an inactive table with rebuild/reshape flags
specified will cause dm-raid to rebuild/reshape on resume and thus start
updating the raid metadata (about the progress).  When the second table
reload, to reset the flags, occurs the constructor accesses the volatile
progress state kept in the raid superblocks.  Because the active mapping
is still processing the rebuild/reshape, that position will be stale by
the time the device is resumed.

In the reshape case, this causes data corruption by processing already
reshaped stripes again.  In the rebuild case, it does _not_ cause data
corruption but instead involves superfluous rebuilds.

Fix by keeping the raid set frozen during the first resume and then
allow the rebuild/reshape during the second resume.

Fixes: 9dbd1aa3 ("dm raid: add reshaping support to the target")
Signed-off-by: NHeinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 4.8+
      d36a1954
    • M
      dm raid: fix raid "check" regression due to improper cleanup in raid_message() · ad470472
      由 Mike Snitzer 提交于 
      While cleaning up awkward branching in raid_message() a raid set "check"
regression was introduced because "check" needs both MD_RECOVERY_SYNC
and MD_RECOVERY_REQUESTED flags set.

Fix this regression by explicitly setting both flags for the "check"
case (like is also done for the "repair" case, but redundant set_bit()s
are perfectly fine because it adds clarity to what is needed in response
to both messages -- in addition this isn't fast path code).

Fixes: 105db599 ("dm raid: cleanup awkward branching in raid_message() option processing")
Reported-by: NHeinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
      ad470472
  7. 25 2月, 2017 1 次提交
  9. 24 2月, 2017 3 次提交
  11. 20 2月, 2017 3 次提交
    • S
      md/raid1: fix a use-after-free bug · af5f42a7
      由 Shaohua Li 提交于 
      Commit fd76863e (RAID1: a new I/O barrier implementation to remove resync
window) introduces a user-after-free bug.
Signed-off-by: NShaohua Li <shli@fb.com>
      af5f42a7
    • C
      RAID1: avoid unnecessary spin locks in I/O barrier code · 824e47da
      由 colyli@suse.de 提交于 
      When I run a parallel reading performan testing on a md raid1 device with
two NVMe SSDs, I observe very bad throughput in supprise: by fio with 64KB
block size, 40 seq read I/O jobs, 128 iodepth, overall throughput is
only 2.7GB/s, this is around 50% of the idea performance number.

The perf reports locking contention happens at allow_barrier() and
wait_barrier() code,
 - 41.41%  fio [kernel.kallsyms]     [k] _raw_spin_lock_irqsave
   - _raw_spin_lock_irqsave
         + 89.92% allow_barrier
         + 9.34% __wake_up
 - 37.30%  fio [kernel.kallsyms]     [k] _raw_spin_lock_irq
   - _raw_spin_lock_irq
         - 100.00% wait_barrier

The reason is, in these I/O barrier related functions,
 - raise_barrier()
 - lower_barrier()
 - wait_barrier()
 - allow_barrier()
They always hold conf->resync_lock firstly, even there are only regular
reading I/Os and no resync I/O at all. This is a huge performance penalty.

The solution is a lockless-like algorithm in I/O barrier code, and only
holding conf->resync_lock when it has to.

The original idea is from Hannes Reinecke, and Neil Brown provides
comments to improve it. I continue to work on it, and make the patch into
current form.

In the new simpler raid1 I/O barrier implementation, there are two
wait barrier functions,
 - wait_barrier()
   Which calls _wait_barrier(), is used for regular write I/O. If there is
   resync I/O happening on the same I/O barrier bucket, or the whole
   array is frozen, task will wait until no barrier on same barrier bucket,
   or the whold array is unfreezed.
 - wait_read_barrier()
   Since regular read I/O won't interfere with resync I/O (read_balance()
   will make sure only uptodate data will be read out), it is unnecessary
   to wait for barrier in regular read I/Os, waiting in only necessary
   when the whole array is frozen.

The operations on conf->nr_pending[idx], conf->nr_waiting[idx], conf->
barrier[idx] are very carefully designed in raise_barrier(),
lower_barrier(), _wait_barrier() and wait_read_barrier(), in order to
avoid unnecessary spin locks in these functions. Once conf->
nr_pengding[idx] is increased, a resync I/O with same barrier bucket index
has to wait in raise_barrier(). Then in _wait_barrier() if no barrier
raised in same barrier bucket index and array is not frozen, the regular
I/O doesn't need to hold conf->resync_lock, it can just increase
conf->nr_pending[idx], and return to its caller. wait_read_barrier() is
very similar to _wait_barrier(), the only difference is it only waits when
array is frozen. For heavy parallel reading I/Os, the lockless I/O barrier
code almostly gets rid of all spin lock cost.

This patch significantly improves raid1 reading peroformance. From my
testing, a raid1 device built by two NVMe SSD, runs fio with 64KB
blocksize, 40 seq read I/O jobs, 128 iodepth, overall throughput
increases from 2.7GB/s to 4.6GB/s (+70%).

Changelog
V4:
- Change conf->nr_queued[] to atomic_t.
- Define BARRIER_BUCKETS_NR_BITS by (PAGE_SHIFT - ilog2(sizeof(atomic_t)))
V3:
- Add smp_mb__after_atomic() as Shaohua and Neil suggested.
- Change conf->nr_queued[] from atomic_t to int.
- Change conf->array_frozen from atomic_t back to int, and use
  READ_ONCE(conf->array_frozen) to check value of conf->array_frozen
  in _wait_barrier() and wait_read_barrier().
- In _wait_barrier() and wait_read_barrier(), add a call to
  wake_up(&conf->wait_barrier) after atomic_dec(&conf->nr_pending[idx]),
  to fix a deadlock between  _wait_barrier()/wait_read_barrier and
  freeze_array().
V2:
- Remove a spin_lock/unlock pair in raid1d().
- Add more code comments to explain why there is no racy when checking two
  atomic_t variables at same time.
V1:
- Original RFC patch for comments.
Signed-off-by: NColy Li <colyli@suse.de>
Cc: Shaohua Li <shli@fb.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Guoqing Jiang <gqjiang@suse.com>
Reviewed-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NShaohua Li <shli@fb.com>
      824e47da
    • C
      RAID1: a new I/O barrier implementation to remove resync window · fd76863e
      由 colyli@suse.de 提交于 
      'Commit 79ef3a8a ("raid1: Rewrite the implementation of iobarrier.")'
introduces a sliding resync window for raid1 I/O barrier, this idea limits
I/O barriers to happen only inside a slidingresync window, for regular
I/Os out of this resync window they don't need to wait for barrier any
more. On large raid1 device, it helps a lot to improve parallel writing
I/O throughput when there are background resync I/Os performing at
same time.

The idea of sliding resync widow is awesome, but code complexity is a
challenge. Sliding resync window requires several variables to work
collectively, this is complexed and very hard to make it work correctly.
Just grep "Fixes: 79ef3a8a" in kernel git log, there are 8 more patches
to fix the original resync window patch. This is not the end, any further
related modification may easily introduce more regreassion.

Therefore I decide to implement a much simpler raid1 I/O barrier, by
removing resync window code, I believe life will be much easier.

The brief idea of the simpler barrier is,
 - Do not maintain a global unique resync window
 - Use multiple hash buckets to reduce I/O barrier conflicts, regular
   I/O only has to wait for a resync I/O when both them have same barrier
   bucket index, vice versa.
 - I/O barrier can be reduced to an acceptable number if there are enough
   barrier buckets

Here I explain how the barrier buckets are designed,
 - BARRIER_UNIT_SECTOR_SIZE
   The whole LBA address space of a raid1 device is divided into multiple
   barrier units, by the size of BARRIER_UNIT_SECTOR_SIZE.
   Bio requests won't go across border of barrier unit size, that means
   maximum bio size is BARRIER_UNIT_SECTOR_SIZE<<9 (64MB) in bytes.
   For random I/O 64MB is large enough for both read and write requests,
   for sequential I/O considering underlying block layer may merge them
   into larger requests, 64MB is still good enough.
   Neil also points out that for resync operation, "we want the resync to
   move from region to region fairly quickly so that the slowness caused
   by having to synchronize with the resync is averaged out over a fairly
   small time frame". For full speed resync, 64MB should take less then 1
   second. When resync is competing with other I/O, it could take up a few
   minutes. Therefore 64MB size is fairly good range for resync.

 - BARRIER_BUCKETS_NR
   There are BARRIER_BUCKETS_NR buckets in total, which is defined by,
        #define BARRIER_BUCKETS_NR_BITS   (PAGE_SHIFT - 2)
        #define BARRIER_BUCKETS_NR        (1<<BARRIER_BUCKETS_NR_BITS)
   this patch makes the bellowed members of struct r1conf from integer
   to array of integers,
        -       int                     nr_pending;
        -       int                     nr_waiting;
        -       int                     nr_queued;
        -       int                     barrier;
        +       int                     *nr_pending;
        +       int                     *nr_waiting;
        +       int                     *nr_queued;
        +       int                     *barrier;
   number of the array elements is defined as BARRIER_BUCKETS_NR. For 4KB
   kernel space page size, (PAGE_SHIFT - 2) indecates there are 1024 I/O
   barrier buckets, and each array of integers occupies single memory page.
   1024 means for a request which is smaller than the I/O barrier unit size
   has ~0.1% chance to wait for resync to pause, which is quite a small
   enough fraction. Also requesting single memory page is more friendly to
   kernel page allocator than larger memory size.

 - I/O barrier bucket is indexed by bio start sector
   If multiple I/O requests hit different I/O barrier units, they only need
   to compete I/O barrier with other I/Os which hit the same I/O barrier
   bucket index with each other. The index of a barrier bucket which a
   bio should look for is calculated by sector_to_idx() which is defined
   in raid1.h as an inline function,
        static inline int sector_to_idx(sector_t sector)
        {
                return hash_long(sector >> BARRIER_UNIT_SECTOR_BITS,
                                BARRIER_BUCKETS_NR_BITS);
        }
   Here sector_nr is the start sector number of a bio.

 - Single bio won't go across boundary of a I/O barrier unit
   If a request goes across boundary of barrier unit, it will be split. A
   bio may be split in raid1_make_request() or raid1_sync_request(), if
   sectors returned by align_to_barrier_unit_end() is smaller than
   original bio size.

Comparing to single sliding resync window,
 - Currently resync I/O grows linearly, therefore regular and resync I/O
   will conflict within a single barrier units. So the I/O behavior is
   similar to single sliding resync window.
 - But a barrier unit bucket is shared by all barrier units with identical
   barrier uinit index, the probability of conflict might be higher
   than single sliding resync window, in condition that writing I/Os
   always hit barrier units which have identical barrier bucket indexs with
   the resync I/Os. This is a very rare condition in real I/O work loads,
   I cannot imagine how it could happen in practice.
 - Therefore we can achieve a good enough low conflict rate with much
   simpler barrier algorithm and implementation.

There are two changes should be noticed,
 - In raid1d(), I change the code to decrease conf->nr_pending[idx] into
   single loop, it looks like this,
        spin_lock_irqsave(&conf->device_lock, flags);
        conf->nr_queued[idx]--;
        spin_unlock_irqrestore(&conf->device_lock, flags);
   This change generates more spin lock operations, but in next patch of
   this patch set, it will be replaced by a single line code,
        atomic_dec(&conf->nr_queueud[idx]);
   So we don't need to worry about spin lock cost here.
 - Mainline raid1 code split original raid1_make_request() into
   raid1_read_request() and raid1_write_request(). If the original bio
   goes across an I/O barrier unit size, this bio will be split before
   calling raid1_read_request() or raid1_write_request(),  this change
   the code logic more simple and clear.
 - In this patch wait_barrier() is moved from raid1_make_request() to
   raid1_write_request(). In raid_read_request(), original wait_barrier()
   is replaced by raid1_read_request().
   The differnece is wait_read_barrier() only waits if array is frozen,
   using different barrier function in different code path makes the code
   more clean and easy to read.
Changelog
V4:
- Add alloc_r1bio() to remove redundant r1bio memory allocation code.
- Fix many typos in patch comments.
- Use (PAGE_SHIFT - ilog2(sizeof(int))) to define BARRIER_BUCKETS_NR_BITS.
V3:
- Rebase the patch against latest upstream kernel code.
- Many fixes by review comments from Neil,
  - Back to use pointers to replace arraries in struct r1conf
  - Remove total_barriers from struct r1conf
  - Add more patch comments to explain how/why the values of
    BARRIER_UNIT_SECTOR_SIZE and BARRIER_BUCKETS_NR are decided.
  - Use get_unqueued_pending() to replace get_all_pendings() and
    get_all_queued()
  - Increase bucket number from 512 to 1024
- Change code comments format by review from Shaohua.
V2:
- Use bio_split() to split the orignal bio if it goes across barrier unit
  bounday, to make the code more simple, by suggestion from Shaohua and
  Neil.
- Use hash_long() to replace original linear hash, to avoid a possible
  confilict between resync I/O and sequential write I/O, by suggestion from
  Shaohua.
- Add conf->total_barriers to record barrier depth, which is used to
  control number of parallel sync I/O barriers, by suggestion from Shaohua.
- In V1 patch the bellowed barrier buckets related members in r1conf are
  allocated in memory page. To make the code more simple, V2 patch moves
  the memory space into struct r1conf, like this,
        -       int                     nr_pending;
        -       int                     nr_waiting;
        -       int                     nr_queued;
        -       int                     barrier;
        +       int                     nr_pending[BARRIER_BUCKETS_NR];
        +       int                     nr_waiting[BARRIER_BUCKETS_NR];
        +       int                     nr_queued[BARRIER_BUCKETS_NR];
        +       int                     barrier[BARRIER_BUCKETS_NR];
  This change is by the suggestion from Shaohua.
- Remove some inrelavent code comments, by suggestion from Guoqing.
- Add a missing wait_barrier() before jumping to retry_write, in
  raid1_make_write_request().
V1:
- Original RFC patch for comments
Signed-off-by: NColy Li <colyli@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Guoqing Jiang <gqjiang@suse.com>
Reviewed-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NShaohua Li <shli@fb.com>
      fd76863e
  13. 17 2月, 2017 17 次提交
  15. 16 2月, 2017 1 次提交
    • M
      md: fast clone bio in bio_clone_mddev() · d7a10308
      由 Ming Lei 提交于 
      Firstly bio_clone_mddev() is used in raid normal I/O and isn't
in resync I/O path.

Secondly all the direct access to bvec table in raid happens on
resync I/O except for write behind of raid1, in which we still
use bio_clone() for allocating new bvec table.

So this patch replaces bio_clone() with bio_clone_fast()
in bio_clone_mddev().

Also kill bio_clone_mddev() and call bio_clone_fast() directly, as
suggested by Christoph Hellwig.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NShaohua Li <shli@fb.com>
      d7a10308