linux.git/drivers/md/md.h, branch v5.3.2

md: introduce mddev_create/destroy_wb_pool for the change of member device

2019-06-20T23:36:00+00:00

Previously, we called rdev_init_wb to avoid potential data
inconsistency when array is created.

Now, we need to call the function and create mempool if a
device is added or just be flaged as "writemostly". So
mddev_create_wb_pool is introduced and called accordingly.
And for safety reason, we mark implicit GFP_NOIO allocation
scope for create mempool during mddev_suspend/mddev_resume.

And mempool should be removed conversely after remove a
member device or its's "writemostly" flag, which is done
by call mddev_destroy_wb_pool.

Reviewed-by: NeilBrown 
Signed-off-by: Guoqing Jiang 
Signed-off-by: Song Liu

md/raid1: fix potential data inconsistency issue with write behind device

2019-06-20T23:35:59+00:00

For write-behind mode, we think write IO is complete once it has
reached all the non-writemostly devices. It works fine for single
queue devices.

But for multiqueue device, if there are lots of IOs come from upper
layer, then the write-behind device could issue those IOs to different
queues, depends on the each queue's delay, so there is no guarantee
that those IOs can arrive in order.

To address the issue, we need to check the collision among write
behind IOs, we can only continue without collision, otherwise wait
for the completion of previous collisioned IO.

And WBCollision is introduced for multiqueue device which is worked
under write-behind mode.

But this patch doesn't handle below cases which could have the data
inconsistency issue as well, these cases will be handled in later
patches.

1. modify max_write_behind by write backlog node.
2. add or remove array's bitmap dynamically.
3. the change of member disk.

Reviewed-by: NeilBrown 
Signed-off-by: Guoqing Jiang 
Signed-off-by: Song Liu

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 47

2019-05-24T15:27:13+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 or at your option any
  later version you should have received a copy of the gnu general
  public license for example usr src linux copying if not write to the
  free software foundation inc 675 mass ave cambridge ma 02139 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 20 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Reviewed-by: Kate Stewart 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520170858.552543146@linutronix.de
Signed-off-by: Greg Kroah-Hartman

md: batch flush requests.

2019-04-01T18:11:48+00:00

Currently if many flush requests are submitted to an md device is quick
succession, they are serialized and can take a long to process them all.
We don't really need to call flush all those times - a single flush call
can satisfy all requests submitted before it started.
So keep track of when the current flush started and when it finished,
allow any pending flush that was requested before the flush started
to complete without waiting any more.

Test results from Xiao:

Test is done on a raid10 device which is created by 4 SSDs. The tool is
dbench.

1. The latest linux stable kernel
  Operation                Count    AvgLat    MaxLat
  --------------------------------------------------
  Deltree                    768    10.509    78.305
  Flush                  2078376     0.013    10.094
  Close                  21787697     0.019    18.821
  LockX                    96580     0.007     3.184
  Mkdir                      384     0.008     0.062
  Rename                 1255883     0.191    23.534
  ReadX                  46495589     0.020    14.230
  WriteX                 14790591     7.123    60.706
  Unlink                 5989118     0.440    54.551
  UnlockX                  96580     0.005     2.736
  FIND_FIRST             10393845     0.042    12.079
  SET_FILE_INFORMATION   2415558     0.129    10.088
  QUERY_FILE_INFORMATION 4711725     0.005     8.462
  QUERY_PATH_INFORMATION 26883327     0.032    21.715
  QUERY_FS_INFORMATION   4929409     0.010     8.238
  NTCreateX              29660080     0.100    53.268

Throughput 1034.88 MB/sec (sync open)  128 clients  128 procs
max_latency=60.712 ms

2. With patch1 "Revert "MD: fix lock contention for flush bios""
  Operation                Count    AvgLat    MaxLat
  --------------------------------------------------
  Deltree                    256     8.326    36.761
  Flush                   693291     3.974   180.269
  Close                  7266404     0.009    36.929
  LockX                    32160     0.006     0.840
  Mkdir                      128     0.008     0.021
  Rename                  418755     0.063    29.945
  ReadX                  15498708     0.007     7.216
  WriteX                 4932310    22.482   267.928
  Unlink                 1997557     0.109    47.553
  UnlockX                  32160     0.004     1.110
  FIND_FIRST             3465791     0.036     7.320
  SET_FILE_INFORMATION    805825     0.015     1.561
  QUERY_FILE_INFORMATION 1570950     0.005     2.403
  QUERY_PATH_INFORMATION 8965483     0.013    14.277
  QUERY_FS_INFORMATION   1643626     0.009     3.314
  NTCreateX              9892174     0.061    41.278

Throughput 345.009 MB/sec (sync open)  128 clients  128 procs
max_latency=267.939 m

3. With patch1 and patch2
  Operation                Count    AvgLat    MaxLat
  --------------------------------------------------
  Deltree                    768     9.570    54.588
  Flush                  2061354     0.666    15.102
  Close                  21604811     0.012    25.697
  LockX                    95770     0.007     1.424
  Mkdir                      384     0.008     0.053
  Rename                 1245411     0.096    12.263
  ReadX                  46103198     0.011    12.116
  WriteX                 14667988     7.375    60.069
  Unlink                 5938936     0.173    30.905
  UnlockX                  95770     0.005     4.147
  FIND_FIRST             10306407     0.041    11.715
  SET_FILE_INFORMATION   2395987     0.048     7.640
  QUERY_FILE_INFORMATION 4672371     0.005     9.291
  QUERY_PATH_INFORMATION 26656735     0.018    19.719
  QUERY_FS_INFORMATION   4887940     0.010     7.654
  NTCreateX              29410811     0.059    28.551

Throughput 1026.21 MB/sec (sync open)  128 clients  128 procs
max_latency=60.075 ms

Cc:  # v4.19+
Tested-by: Xiao Ni 
Signed-off-by: NeilBrown 
Signed-off-by: Song Liu 
Signed-off-by: Jens Axboe

Revert "MD: fix lock contention for flush bios"

2019-04-01T18:11:48+00:00

This reverts commit 5a409b4f56d50b212334f338cb8465d65550cd85.

This patch has two problems.

1/ it make multiple calls to submit_bio() from inside a make_request_fn.
 The bios thus submitted will be queued on current->bio_list and not
 submitted immediately.  As the bios are allocated from a mempool,
 this can theoretically result in a deadlock - all the pool of requests
 could be in various ->bio_list queues and a subsequent mempool_alloc
 could block waiting for one of them to be released.

2/ It aims to handle a case when there are many concurrent flush requests.
  It handles this by submitting many requests in parallel - all of which
  are identical and so most of which do nothing useful.
  It would be more efficient to just send one lower-level request, but
  allow that to satisfy multiple upper-level requests.

Fixes: 5a409b4f56d5 ("MD: fix lock contention for flush bios")
Cc:  # v4.19+
Tested-by: Xiao Ni 
Signed-off-by: NeilBrown 
Signed-off-by: Song Liu 
Signed-off-by: Jens Axboe

md-cluster/raid10: support add disk under grow mode

2018-10-18T16:34:56+00:00

For clustered raid10 scenario, we need to let all the nodes
know about that a new disk is added to the array, and the
reshape caused by add new member just need to be happened in
one node, but other nodes should know about the change.

Since reshape means read data from somewhere (which is already
used by array) and write data to unused region. Obviously, it
is awful if one node is reading data from address while another
node is writing to the same address. Considering we have
implemented suspend writes in the resyncing area, so we can
just broadcast the reading address to other nodes to avoid the
trouble.

For master node, it would call reshape_request then update sb
during the reshape period. To avoid above trouble, we call
resync_info_update to send RESYNC message in reshape_request.

Then from slave node's view, it receives two type messages:
1. RESYNCING message
Slave node add the address (where master node reading data from)
to suspend list.

2. METADATA_UPDATED message
Once slave nodes know the reshaping is started in master node,
it is time to update reshape position and call start_reshape to
follow master node's step. After reshape is done, only reshape
position is need to be updated, so the majority task of reshaping
is happened on the master node.

Reviewed-by: NeilBrown 
Signed-off-by: Guoqing Jiang 
Signed-off-by: Shaohua Li

md-cluster: show array's status more accurate

2018-07-05T18:17:01+00:00

When resync or recovery is happening in one node,
other nodes don't show the appropriate info now.

For example, when create an array in master node
without "--assume-clean", then assemble the array
in slave nodes, you can see "resync=PENDING" when
read /proc/mdstat in slave nodes. However, the info
is confusing since "PENDING" status is introduced
for start array in read-only mode.

We introduce RESYNCING_REMOTE flag to indicate that
resync thread is running in remote node. The flags
is set when node receive RESYNCING msg. And we clear
the REMOTE flag in following cases:

1. resync or recover is finished in master node,
   which means slaves receive msg with both lo
   and hi are set to 0.
2. node continues resync/recovery in recover_bitmaps.
3. when resync_finish is called.

Then we show accurate information in status_resync
by check REMOTE flags and with other conditions.

Signed-off-by: Guoqing Jiang 
Reviewed-by: NeilBrown 
Signed-off-by: Shaohua Li

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

2018-06-09T19:01:36+00:00

Pull MD updates from Shaohua Li:
 "A few fixes of MD for this merge window. Mostly bug fixes:

   - raid5 stripe batch fix from Amy

   - Read error handling for raid1 FailFast device from Gioh

   - raid10 recovery NULL pointer dereference fix from Guoqing

   - Support write hint for raid5 stripe cache from Mariusz

   - Fixes for device hot add/remove from Neil and Yufen

   - Improve flush bio scalability from Xiao"

* 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md:
  MD: fix lock contention for flush bios
  md/raid5: Assigning NULL to sh->batch_head before testing bit R5_Overlap of a stripe
  md/raid1: add error handling of read error from FailFast device
  md: fix NULL dereference of mddev->pers in remove_and_add_spares()
  raid5: copy write hint from origin bio to stripe
  md: fix two problems with setting the "re-add" device state.
  raid10: check bio in r10buf_pool_free to void NULL pointer dereference
  md: fix an error code format and remove unsed bio_sector

md: convert to bioset_init()/mempool_init()

2018-05-30T21:33:32+00:00

Convert md to embedded bio sets.

Signed-off-by: Kent Overstreet 
Signed-off-by: Jens Axboe

MD: fix lock contention for flush bios

2018-05-21T16:30:26+00:00

There is a lock contention when there are many processes which send flush bios
to md device. eg. Create many lvs on one raid device and mkfs.xfs on each lv.

Now it just can handle flush request sequentially. It needs to wait mddev->flush_bio
to be NULL, otherwise get mddev->lock.

This patch remove mddev->flush_bio and handle flush bio asynchronously.
I did a test with command dbench -s 128 -t 300. This is the test result:

=================Without the patch============================
 Operation                Count    AvgLat    MaxLat
 --------------------------------------------------
 Flush                    11165   167.595  5879.560
 Close                   107469     1.391  2231.094
 LockX                      384     0.003     0.019
 Rename                    5944     2.141  1856.001
 ReadX                   208121     0.003     0.074
 WriteX                   98259  1925.402 15204.895
 Unlink                   25198    13.264  3457.268
 UnlockX                    384     0.001     0.009
 FIND_FIRST               47111     0.012     0.076
 SET_FILE_INFORMATION     12966     0.007     0.065
 QUERY_FILE_INFORMATION   27921     0.004     0.085
 QUERY_PATH_INFORMATION  124650     0.005     5.766
 QUERY_FS_INFORMATION     22519     0.003     0.053
 NTCreateX               141086     4.291  2502.812

Throughput 3.7181 MB/sec (sync open)  128 clients  128 procs  max_latency=15204.905 ms

=================With the patch============================
 Operation                Count    AvgLat    MaxLat
 --------------------------------------------------
 Flush                     4500   174.134   406.398
 Close                    48195     0.060   467.062
 LockX                      256     0.003     0.029
 Rename                    2324     0.026     0.360
 ReadX                    78846     0.004     0.504
 WriteX                   66832   562.775  1467.037
 Unlink                    5516     3.665  1141.740
 UnlockX                    256     0.002     0.019
 FIND_FIRST               16428     0.015     0.313
 SET_FILE_INFORMATION      6400     0.009     0.520
 QUERY_FILE_INFORMATION   17865     0.003     0.089
 QUERY_PATH_INFORMATION   47060     0.078   416.299
 QUERY_FS_INFORMATION      7024     0.004     0.032
 NTCreateX                55921     0.854  1141.452

Throughput 11.744 MB/sec (sync open)  128 clients  128 procs  max_latency=1467.041 ms

The test is done on raid1 disk with two rotational disks

V5: V4 is more complicated than the version with memory pool. So revert to the memory pool
version

V4: use address of fbio to do hash to choose free flush info.
V3:
Shaohua suggests mempool is overkill. In v3 it allocs memory during creating raid device
and uses a simple bitmap to record which resource is free.

Fix a bug from v2. It should set flush_pending to 1 at first.

V2:
Neil pointed out two problems. One is counting error problem and another is return value
when allocat memory fails.
1. counting error problem
This isn't safe.  It is only safe to call rdev_dec_pending() on rdevs
that you previously called
                          atomic_inc(&rdev->nr_pending);
If an rdev was added to the list between the start and end of the flush,
this will do something bad.

Now it doesn't use bio_chain. It uses specified call back function for each
flush bio.
2. Returned on IO error when kmalloc fails is wrong.
I use mempool suggested by Neil in V2
3. Fixed some places pointed by Guoqing

Suggested-by: Ming Lei 
Signed-off-by: Xiao Ni 
Signed-off-by: Shaohua Li