1. 09 Feb, 2019 10 commits
    • Coly Li's avatar
      bcache: add sysfs_strtoul_bool() for setting bit-field variables · e4db37fb
      Coly Li authored
      When setting bool values via sysfs interface, e.g. writeback_metadata,
      if writing 1 into writeback_metadata file, dc->writeback_metadata is
      set to 1, but if writing 2 into the file, dc->writeback_metadata is
      0. This is misleading, a better result should be 1 for all non-zero
      input value.
      
      It is because dc->writeback_metadata is a bit-field variable, and
      current code simply use d_strtoul() to convert a string into integer
      and takes the lowest bit value. To fix such error, we need a routine
      to convert the input string into unsigned integer, and set target
      variable to 1 if the converted integer is non-zero.
      
      This patch introduces a new macro called sysfs_strtoul_bool(), it can
      be used to convert input string into bool value, we can use it to set
      bool value for bit-field vairables.
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      e4db37fb
    • Coly Li's avatar
      bcache: fix input overflow to sequential_cutoff · 8c27a395
      Coly Li authored
      People may set sequential_cutoff of a cached device via sysfs file,
      but current code does not check input value overflow. E.g. if value
      4294967295 (UINT_MAX) is written to file sequential_cutoff, its value
      is 4GB, but if 4294967296 (UINT_MAX + 1) is written into, its value
      will be 0. This is an unexpected behavior.
      
      This patch replaces d_strtoi_h() by sysfs_strtoul_clamp() to convert
      input string to unsigned integer value, and limit its range in
      [0, UINT_MAX]. Then the input overflow can be fixed.
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      8c27a395
    • Coly Li's avatar
      bcache: fix input integer overflow of congested threshold · f54478c6
      Coly Li authored
      Cache set congested threshold values congested_read_threshold_us and
      congested_write_threshold_us can be set via sysfs interface. These
      two values are 'unsigned int' type, but sysfs interface uses strtoul
      to convert input string. So if people input a large number like
      9999999999, the value indeed set is 1410065407, which is not expected
      behavior.
      
      This patch replaces sysfs_strtoul() by sysfs_strtoul_clamp() when
      convert input string to unsigned int value, and set value range in
      [0, UINT_MAX], to avoid the above integer overflow errors.
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      f54478c6
    • Coly Li's avatar
      bcache: improve sysfs_strtoul_clamp() · 596b5a5d
      Coly Li authored
      Currently sysfs_strtoul_clamp() is defined as,
       82 #define sysfs_strtoul_clamp(file, var, min, max)                   \
       83 do {                                                               \
       84         if (attr == &sysfs_ ## file)                               \
       85                 return strtoul_safe_clamp(buf, var, min, max)      \
       86                         ?: (ssize_t) size;                         \
       87 } while (0)
      
      The problem is, if bit width of var is less then unsigned long, min and
      max may not protect var from integer overflow, because overflow happens
      in strtoul_safe_clamp() before checking min and max.
      
      To fix such overflow in sysfs_strtoul_clamp(), to make min and max take
      effect, this patch adds an unsigned long variable, and uses it to macro
      strtoul_safe_clamp() to convert an unsigned long value in range defined
      by [min, max]. Then assign this value to var. By this method, if bit
      width of var is less than unsigned long, integer overflow won't happen
      before min and max are checking.
      
      Now sysfs_strtoul_clamp() can properly handle smaller data type like
      unsigned int, of cause min and max should be defined in range of
      unsigned int too.
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      596b5a5d
    • Tang Junhui's avatar
      bcache: treat stale && dirty keys as bad keys · 58ac3230
      Tang Junhui authored
      Stale && dirty keys can be produced in the follow way:
      After writeback in write_dirty_finish(), dirty keys k1 will
      replace by clean keys k2
      ==>ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
      ==>btree_insert_fn(struct btree_op *b_op, struct btree *b)
      ==>static int bch_btree_insert_node(struct btree *b,
             struct btree_op *op,
             struct keylist *insert_keys,
             atomic_t *journal_ref,
      Then two steps:
      A) update k1 to k2 in btree node memory;
         bch_btree_insert_keys(b, op, insert_keys, replace_key)
      B) Write the bset(contains k2) to cache disk by a 30s delay work
         bch_btree_leaf_dirty(b, journal_ref).
      But before the 30s delay work write the bset to cache device,
      these things happened:
      A) GC works, and reclaim the bucket k2 point to;
      B) Allocator works, and invalidate the bucket k2 point to,
         and increase the gen of the bucket, and place it into free_inc
         fifo;
      C) Until now, the 30s delay work still does not finish work,
         so in the disk, the key still is k1, it is dirty and stale
         (its gen is smaller than the gen of the bucket). and then the
         machine power off suddenly happens;
      D) When the machine power on again, after the btree reconstruction,
         the stale dirty key appear.
      
      In bch_extent_bad(), when expensive_debug_checks is off, it would
      treat the dirty key as good even it is stale keys, and it would
      cause bellow probelms:
      A) In read_dirty() it would cause machine crash:
         BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));
      B) It could be worse when reads hits stale dirty keys, it would
         read old incorrect data.
      
      This patch tolerate the existence of these stale && dirty keys,
      and treat them as bad key in bch_extent_bad().
      
      (Coly Li: fix indent which was modified by sender's email client)
      Signed-off-by: default avatarTang Junhui <tang.junhui.linux@gmail.com>
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      58ac3230
    • Colin Ian King's avatar
      bcache: fix indentation issue, remove tabs on a hunk of code · e8cf978d
      Colin Ian King authored
      There is a hunk of code that is indented one level too deep, fix this
      by removing the extra tabs.
      Signed-off-by: default avatarColin Ian King <colin.king@canonical.com>
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      e8cf978d
    • Coly Li's avatar
      bcache: export backing_dev_uuid via sysfs · d4610456
      Coly Li authored
      When there are multiple bcache devices, after a reboot the name of
      bcache devices may change (e.g. current /dev/bcache1 was /dev/bcache0
      before reboot). Therefore we need the backing device UUID (sb.uuid) to
      identify each bcache device.
      
      Backing device uuid can be found by program bcache-super-show, but
      directly exporting backing_dev_uuid by sysfs file
      /sys/block/bcache<?>/bcache/backing_dev_uuid is a much simpler method.
      
      With backing_dev_uuid, and partition uuids from /dev/disk/by-partuuid/,
      now we can identify each bcache device and its partitions conveniently.
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      d4610456
    • Coly Li's avatar
      bcache: export backing_dev_name via sysfs · 926d1946
      Coly Li authored
      This patch export dc->backing_dev_name to sysfs file
      /sys/block/bcache<?>/bcache/backing_dev_name, then people or user space
      tools may know the backing device name of this bcache device.
      
      Of cause it can be done by parsing sysfs links, but this method can be
      much simpler to find the link between bcache device and backing device.
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      926d1946
    • Coly Li's avatar
      bcache: not use hard coded memset size in bch_cache_accounting_clear() · 83ff9318
      Coly Li authored
      In stats.c:bch_cache_accounting_clear(), a hard coded number '7' is
      used in memset(). It is because in struct cache_stats, there are 7
      atomic_t type members. This is not good when new members added into
      struct stats, the hard coded number will only clear part of memory.
      
      This patch replaces 'sizeof(unsigned long) * 7' by more generic
      'sizeof(struct cache_stats))', to avoid potential error if new
      member added into struct cache_stats.
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      83ff9318
    • Daniel Axtens's avatar
      bcache: never writeback a discard operation · 9951379b
      Daniel Axtens authored
      Some users see panics like the following when performing fstrim on a
      bcached volume:
      
      [  529.803060] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
      [  530.183928] #PF error: [normal kernel read fault]
      [  530.412392] PGD 8000001f42163067 P4D 8000001f42163067 PUD 1f42168067 PMD 0
      [  530.750887] Oops: 0000 [#1] SMP PTI
      [  530.920869] CPU: 10 PID: 4167 Comm: fstrim Kdump: loaded Not tainted 5.0.0-rc1+ #3
      [  531.290204] Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 Gen9, BIOS P89 12/27/2015
      [  531.693137] RIP: 0010:blk_queue_split+0x148/0x620
      [  531.922205] Code: 60 38 89 55 a0 45 31 db 45 31 f6 45 31 c9 31 ff 89 4d 98 85 db 0f 84 7f 04 00 00 44 8b 6d 98 4c 89 ee 48 c1 e6 04 49 03 70 78 <8b> 46 08 44 8b 56 0c 48
      8b 16 44 29 e0 39 d8 48 89 55 a8 0f 47 c3
      [  532.838634] RSP: 0018:ffffb9b708df39b0 EFLAGS: 00010246
      [  533.093571] RAX: 00000000ffffffff RBX: 0000000000046000 RCX: 0000000000000000
      [  533.441865] RDX: 0000000000000200 RSI: 0000000000000000 RDI: 0000000000000000
      [  533.789922] RBP: ffffb9b708df3a48 R08: ffff940d3b3fdd20 R09: 0000000000000000
      [  534.137512] R10: ffffb9b708df3958 R11: 0000000000000000 R12: 0000000000000000
      [  534.485329] R13: 0000000000000000 R14: 0000000000000000 R15: ffff940d39212020
      [  534.833319] FS:  00007efec26e3840(0000) GS:ffff940d1f480000(0000) knlGS:0000000000000000
      [  535.224098] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      [  535.504318] CR2: 0000000000000008 CR3: 0000001f4e256004 CR4: 00000000001606e0
      [  535.851759] Call Trace:
      [  535.970308]  ? mempool_alloc_slab+0x15/0x20
      [  536.174152]  ? bch_data_insert+0x42/0xd0 [bcache]
      [  536.403399]  blk_mq_make_request+0x97/0x4f0
      [  536.607036]  generic_make_request+0x1e2/0x410
      [  536.819164]  submit_bio+0x73/0x150
      [  536.980168]  ? submit_bio+0x73/0x150
      [  537.149731]  ? bio_associate_blkg_from_css+0x3b/0x60
      [  537.391595]  ? _cond_resched+0x1a/0x50
      [  537.573774]  submit_bio_wait+0x59/0x90
      [  537.756105]  blkdev_issue_discard+0x80/0xd0
      [  537.959590]  ext4_trim_fs+0x4a9/0x9e0
      [  538.137636]  ? ext4_trim_fs+0x4a9/0x9e0
      [  538.324087]  ext4_ioctl+0xea4/0x1530
      [  538.497712]  ? _copy_to_user+0x2a/0x40
      [  538.679632]  do_vfs_ioctl+0xa6/0x600
      [  538.853127]  ? __do_sys_newfstat+0x44/0x70
      [  539.051951]  ksys_ioctl+0x6d/0x80
      [  539.212785]  __x64_sys_ioctl+0x1a/0x20
      [  539.394918]  do_syscall_64+0x5a/0x110
      [  539.568674]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
      
      We have observed it where both:
      1) LVM/devmapper is involved (bcache backing device is LVM volume) and
      2) writeback cache is involved (bcache cache_mode is writeback)
      
      On one machine, we can reliably reproduce it with:
      
       # echo writeback > /sys/block/bcache0/bcache/cache_mode
         (not sure whether above line is required)
       # mount /dev/bcache0 /test
       # for i in {0..10}; do
      	file="$(mktemp /test/zero.XXX)"
      	dd if=/dev/zero of="$file" bs=1M count=256
      	sync
      	rm $file
          done
        # fstrim -v /test
      
      Observing this with tracepoints on, we see the following writes:
      
      fstrim-18019 [022] .... 91107.302026: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0  DS 4260112 + 196352 hit 0 bypass 1
      fstrim-18019 [022] .... 91107.302050: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0  DS 4456464 + 262144 hit 0 bypass 1
      fstrim-18019 [022] .... 91107.302075: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0  DS 4718608 + 81920 hit 0 bypass 1
      fstrim-18019 [022] .... 91107.302094: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0  DS 5324816 + 180224 hit 0 bypass 1
      fstrim-18019 [022] .... 91107.302121: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0  DS 5505040 + 262144 hit 0 bypass 1
      fstrim-18019 [022] .... 91107.302145: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0  DS 5767184 + 81920 hit 0 bypass 1
      fstrim-18019 [022] .... 91107.308777: bcache_write: 73f95583-561c-408f-a93a-4cbd2498f5c8 inode 0  DS 6373392 + 180224 hit 1 bypass 0
      <crash>
      
      Note the final one has different hit/bypass flags.
      
      This is because in should_writeback(), we were hitting a case where
      the partial stripe condition was returning true and so
      should_writeback() was returning true early.
      
      If that hadn't been the case, it would have hit the would_skip test, and
      as would_skip == s->iop.bypass == true, should_writeback() would have
      returned false.
      
      Looking at the git history from 'commit 72c27061 ("bcache: Write out
      full stripes")', it looks like the idea was to optimise for raid5/6:
      
             * If a stripe is already dirty, force writes to that stripe to
      	 writeback mode - to help build up full stripes of dirty data
      
      To fix this issue, make sure that should_writeback() on a discard op
      never returns true.
      
      More details of debugging:
      https://www.spinics.net/lists/linux-bcache/msg06996.html
      
      Previous reports:
       - https://bugzilla.kernel.org/show_bug.cgi?id=201051
       - https://bugzilla.kernel.org/show_bug.cgi?id=196103
       - https://www.spinics.net/lists/linux-bcache/msg06885.html
      
      (Coly Li: minor modification to follow maximum 75 chars per line rule)
      
      Cc: Kent Overstreet <koverstreet@google.com>
      Cc: stable@vger.kernel.org
      Fixes: 72c27061 ("bcache: Write out full stripes")
      Signed-off-by: default avatarDaniel Axtens <dja@axtens.net>
      Signed-off-by: default avatarColy Li <colyli@suse.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      9951379b
  2. 08 Feb, 2019 2 commits
    • Aleksei Zakharov's avatar
      block: avoid setting nr_requests to current value · e5fa8140
      Aleksei Zakharov authored
      There's no reason to freeze queue and set nr_requests value
      if current value is the same.
      Signed-off-by: default avatarAleksei Zakharov <zakharov.a.g@yandex.ru>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      e5fa8140
    • Guenter Roeck's avatar
      cdrom: Fix race condition in cdrom_sysctl_register · f25191bb
      Guenter Roeck authored
      The following traceback is sometimes seen when booting an image in qemu:
      
      [   54.608293] cdrom: Uniform CD-ROM driver Revision: 3.20
      [   54.611085] Fusion MPT base driver 3.04.20
      [   54.611877] Copyright (c) 1999-2008 LSI Corporation
      [   54.616234] Fusion MPT SAS Host driver 3.04.20
      [   54.635139] sysctl duplicate entry: /dev/cdrom//info
      [   54.639578] CPU: 0 PID: 266 Comm: kworker/u4:5 Not tainted 5.0.0-rc5 #1
      [   54.639578] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
      [   54.641273] Workqueue: events_unbound async_run_entry_fn
      [   54.641273] Call Trace:
      [   54.641273]  dump_stack+0x67/0x90
      [   54.641273]  __register_sysctl_table+0x50b/0x570
      [   54.641273]  ? rcu_read_lock_sched_held+0x6f/0x80
      [   54.641273]  ? kmem_cache_alloc_trace+0x1c7/0x1f0
      [   54.646814]  __register_sysctl_paths+0x1c8/0x1f0
      [   54.646814]  cdrom_sysctl_register.part.7+0xc/0x5f
      [   54.646814]  register_cdrom.cold.24+0x2a/0x33
      [   54.646814]  sr_probe+0x4bd/0x580
      [   54.646814]  ? __driver_attach+0xd0/0xd0
      [   54.646814]  really_probe+0xd6/0x260
      [   54.646814]  ? __driver_attach+0xd0/0xd0
      [   54.646814]  driver_probe_device+0x4a/0xb0
      [   54.646814]  ? __driver_attach+0xd0/0xd0
      [   54.646814]  bus_for_each_drv+0x73/0xc0
      [   54.646814]  __device_attach+0xd6/0x130
      [   54.646814]  bus_probe_device+0x9a/0xb0
      [   54.646814]  device_add+0x40c/0x670
      [   54.646814]  ? __pm_runtime_resume+0x4f/0x80
      [   54.646814]  scsi_sysfs_add_sdev+0x81/0x290
      [   54.646814]  scsi_probe_and_add_lun+0x888/0xc00
      [   54.646814]  ? scsi_autopm_get_host+0x21/0x40
      [   54.646814]  __scsi_add_device+0x116/0x130
      [   54.646814]  ata_scsi_scan_host+0x93/0x1c0
      [   54.646814]  async_run_entry_fn+0x34/0x100
      [   54.646814]  process_one_work+0x237/0x5e0
      [   54.646814]  worker_thread+0x37/0x380
      [   54.646814]  ? rescuer_thread+0x360/0x360
      [   54.646814]  kthread+0x118/0x130
      [   54.646814]  ? kthread_create_on_node+0x60/0x60
      [   54.646814]  ret_from_fork+0x3a/0x50
      
      The only sensible explanation is that cdrom_sysctl_register() is called
      twice, once from the module init function and once from register_cdrom().
      cdrom_sysctl_register() is not mutex protected and may happily execute
      twice if the second call is made before the first call is complete.
      
      Use a static atomic to ensure that the function is executed exactly once.
      Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      f25191bb
  3. 04 Feb, 2019 6 commits
  4. 01 Feb, 2019 2 commits
  5. 31 Jan, 2019 15 commits
    • Paolo Valente's avatar
      block, bfq: fix in-service-queue check for queue merging · 058fdecc
      Paolo Valente authored
      When a new I/O request arrives for a bfq_queue, say Q, bfq checks
      whether that request is close to
      (a) the head request of some other queue waiting to be served, or
      (b) the last request dispatched for the in-service queue (in case Q
      itself is not the in-service queue)
      
      If a queue, say Q2, is found for which the above condition holds, then
      bfq merges Q and Q2, to hopefully get a more sequential I/O in the
      resulting merged queue, and thus a possibly higher throughput.
      
      Case (b) is checked by comparing the new request for Q with the last
      request dispatched, assuming that the latter necessarily belonged to the
      in-service queue. Unfortunately, this assumption is no longer always
      correct, since commit d0edc247 ("block, bfq: inject other-queue I/O
      into seeky idle queues on NCQ flash").
      
      When the assumption does not hold, queues that must not be merged may be
      merged, causing unexpected loss of control on per-queue service
      guarantees.
      
      This commit solves this problem by adding an extra field, which stores
      the actual last request dispatched for the in-service queue, and by
      using this new field to correctly check case (b).
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      058fdecc
    • Paolo Valente's avatar
      block, bfq: do not overcharge writes in asymmetric scenarios · 02a6d787
      Paolo Valente authored
      Writes tend to starve reads. bfq counters this problem by overcharging
      writes with an inflated service w.r.t. the actual service (number of
      sector written) they receive.
      
      Yet his overcharging is useless, and actually causes unfairness in the
      opposite direction, when bfq happens to be enforcing strong I/O control.
      bfq does this enforcing when the scenario is asymmetric, i.e., when some
      bfq_queue or group of bfq_queues is to be granted a different bandwidth
      than some other bfq_queue or group of bfq_queues. So, in such a
      scenario, this commit disables write overcharging.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      02a6d787
    • Paolo Valente's avatar
      block, bfq: port commit "cfq-iosched: improve hw_tag detection" · b3c34981
      Paolo Valente authored
      The original commit is commit 1a1238a7 ("cfq-iosched: improve hw_tag
      detection") and has the following commit message:
      
      If active queue hasn't enough requests and idle window opens, cfq will
      not dispatch sufficient requests to hardware. In such situation, current
      code will zero hw_tag. But this is because cfq doesn't dispatch enough
      requests instead of hardware queue doesn't work. Don't zero hw_tag in
      such case.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      b3c34981
    • Paolo Valente's avatar
      block, bfq: reduce threshold for detecting command queueing · a3c92560
      Paolo Valente authored
      bfq simple heuristic from cfq for detecting whether the drive performs
      command queueing: check whether the average number of in-flight requests
      is above a given threshold. Unfortunately this heuristic does fail to
      detect queueing (on drives with queueing) if processes doing I/O are few
      and issue I/O with a low depth.
      
      To reduce false negatives, this commit lowers the threshold.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      a3c92560
    • Paolo Valente's avatar
      block, bfq: fix queue removal from weights tree · 9dee8b3b
      Paolo Valente authored
      bfq maintains an ordered list, through a red-black tree, of unique
      weights of active bfq_queues. This list is used to detect whether there
      are active queues with differentiated weights. The weight of a queue is
      removed from the list when both the following two conditions become
      true:
      
      (1) the bfq_queue is flagged as inactive
      (2) the has no in-flight request any longer;
      
      Unfortunately, in the rare cases where condition (2) becomes true before
      condition (1), the removal fails, because the function to remove the
      weight of the queue (bfq_weights_tree_remove) is rightly invoked in the
      path that deactivates the bfq_queue, but mistakenly invoked *before* the
      function that actually performs the deactivation (bfq_deactivate_bfqq).
      
      This commits moves the invocation of bfq_weights_tree_remove for
      condition (1) to after bfq_deactivate_bfqq. As a consequence of this
      move, it is necessary to add a further reference to the queue when the
      weight of a queue is added, because the queue might otherwise be freed
      before bfq_weights_tree_remove is invoked. This commit adds this
      reference and makes all related modifications.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      9dee8b3b
    • Paolo Valente's avatar
      block, bfq: fix sequential rq detection in rate estimation · d87447d8
      Paolo Valente authored
      In bfq_update_peak_rate, to check whether an I/O request rq is
      sequential, only the seek distance of rq w.r.t. the last request
      dispatched is controlled. This is not sufficient for non-rotational
      storage, where the size of rq is at least as relevant. This commit adds
      the missing control.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      d87447d8
    • Paolo Valente's avatar
      block, bfq: unconditionally plug I/O in asymmetric scenarios · 530c4cbb
      Paolo Valente authored
      bfq detects the creation of multiple bfq_queues shortly after each
      other, namely a burst of queue creations in the terminology used in the
      code. If the burst is large, then no queue in the burst is granted
      - either I/O-dispatch plugging when the queue remains temporarily idle
        while in service;
      - or weight raising, because it causes even longer plugging.
      
      In fact, such a plugging tends to lower throughput, while these bursts
      are typically due to applications or services that spawn multiple
      processes, to reach a common goal as soon as possible. Examples are a
      "git grep" or the booting of a system.
      
      Unfortunately, disabling plugging may cause a loss of service guarantees
      in asymmetric scenarios, i.e., if queue weights are differentiated or if
      more than one group is active.
      
      This commit addresses this issue by no longer disabling I/O-dispatch
      plugging for queues in large bursts.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      530c4cbb
    • Paolo Valente's avatar
      block, bfq: do not plug I/O of in-service queue when harmful · ac8b0cb4
      Paolo Valente authored
      If the in-service bfq_queue is sync and remains temporarily idle, then
      I/O dispatching (from other queues) may be plugged. It may be dome for
      two reasons: either to boost throughput, or to preserve the bandwidth
      share of the in-service queue. In the first case, if the I/O of the
      in-service queue, when it finally arrives, consists only of one small
      I/O request, then it makes sense to plug even the I/O of the in-service
      queue. In fact, serving such a small request immediately is likely to
      lower throughput instead of boosting it, whereas waiting a little bit is
      likely to let that request grow, thanks to request merging, and become
      more profitable in terms of throughput (this is likely to happen exactly
      because the I/O of the queue has been detected to boost throughput).
      
      On the opposite end, if I/O dispatching is being plugged only to
      preserve the bandwidth of the in-service queue, then it would be better
      not to plug also the I/O of the in-service queue, because such a
      plugging is likely to cause only loss of bandwidth for the queue.
      
      Unfortunately, no distinction is made between the two cases, and the I/O
      of the in-service queue is always plugged in case just a small I/O
      request arrives. This commit draws this missing distinction and does not
      perform harmful plugging.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      ac8b0cb4
    • Paolo Valente's avatar
      block, bfq: split function bfq_better_to_idle · 05c2f5c3
      Paolo Valente authored
      This is a preparatory commit for commits that need to check only one of
      the two main reasons for idling. This change should also improve the
      quality of the code a little bit, by splitting a function that contains
      very long, non-trivial and little related comments.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      05c2f5c3
    • Paolo Valente's avatar
      block, bfq: consider also ioprio classes in symmetry detection · 73d58118
      Paolo Valente authored
      In asymmetric scenarios, i.e., when some bfq_queue or bfq_group needs to
      be guaranteed a different bandwidth than other bfq_queues or bfq_groups,
      these service guaranteed can be provided only by plugging I/O dispatch,
      completely or partially, when the queue in service remains temporarily
      empty. A case where asymmetry is particularly strong is when some active
      bfq_queues belong to a higher-priority class than some other active
      bfq_queues. Unfortunately, this important case is not considered at all
      in the code for detecting asymmetric scenarios. This commit adds the
      missing logic.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      73d58118
    • Paolo Valente's avatar
      block, bfq: remove case of redirected bic from insert_request · 03e565e4
      Paolo Valente authored
      Before commit 18e5a57d ("block, bfq: postpone rq preparation to
      insert or merge"), the destination queue for a request was chosen by a
      different hook than the one that then inserted the request. So, between
      the execution of the two hooks, the bic of the process generating the
      request could happen to be redirected to a different bfq_queue. As a
      consequence, the destination bfq_queue stored in the request could be
      wrong. Such an event does not need to ba handled any longer.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      03e565e4
    • Paolo Valente's avatar
      block, bfq: make sure queue budgets are not below service received · f3218ad8
      Paolo Valente authored
      With some unlucky sequences of events, the function bfq_updated_next_req
      updates the current budget of a bfq_queue to a lower value than the
      service received by the queue using such a budget. Unfortunately, if
      this happens, then the return value of the function bfq_bfqq_budget_left
      becomes inconsistent. This commit solves this problem by lower-bounding
      the budget computed in bfq_updated_next_req to the service currently
      charged to the queue.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      f3218ad8
    • Paolo Valente's avatar
      block, bfq: avoid selecting a queue w/o budget · 218cb897
      Paolo Valente authored
      To boost throughput on devices with internal queueing and in scenarios
      where device idling is not strictly needed, bfq immediately starts
      serving a new bfq_queue if the in-service bfq_queue remains without
      pending I/O, even if new I/O may arrive soon for the latter queue. Then,
      if such I/O actually arrives soon, bfq preempts the new in-service
      bfq_queue so as to give the previous queue a chance to go on being
      served (in case the previous queue should actually be the one to be
      served, according to its timestamps).
      
      However, the in-service bfq_queue, say Q, may also be without further
      budget when it remains also pending I/O. Since bfq changes budgets
      dynamically to fit the needs of bfq_queues, this happens more often than
      one may expect. If this happens, then there is no point in trying to go
      on serving Q when new I/O arrives for it soon: Q would be expired
      immediately after being selected for service. This would only cause
      useless overhead. This commit avoids such a useless selection.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      218cb897
    • Paolo Valente's avatar
      block, bfq: do not consider interactive queues in srt filtering · 20cd3245
      Paolo Valente authored
      The speed at which a bfq_queue receives I/O is one of the parameters by
      which bfq decides whether the queue is soft real-time (i.e., whether the
      queue contains the I/O of a soft real-time application). In particular,
      when a bfq_queue remains without outstanding I/O requests, bfq computes
      the minimum time instant, named soft_rt_next_start, at which the next
      request of the queue may arrive for the queue to be deemed as soft real
      time.
      
      Unfortunately this filtering may cause problems with a queue in
      interactive weight raising. In fact, such a queue may be conveying the
      I/O needed to load a soft real-time application. The latter will
      actually exhibit a soft real-time I/O pattern after it finally starts
      doing its job. But, if soft_rt_next_start is updated for an interactive
      bfq_queue, and the queue has received a lot of service before remaining
      with no outstanding request (likely to happen on a fast device), then
      soft_rt_next_start is assigned such a high value that, for a very long
      time, the queue is prevented from being possibly considered as soft real
      time.
      
      This commit removes the updating of soft_rt_next_start for bfq_queues in
      interactive weight raising.
      Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      20cd3245
    • Christoph Hellwig's avatar
      mtip32xx: ѕtop abusing the managed resource APIs · 22cb4e68
      Christoph Hellwig authored
      The mtip32xx driver uses managed resources for DMA coherent memory
      and irqs, but then always pairs them with free calls anyway, making
      the resource tracking rather pointless.  Given some DMA allocations
      are transient anyway, the irq freeing seems to require ordering vs
      other hardware access the best solution seems to be to stop using
      the managed resource API entirely.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      22cb4e68
  6. 27 Jan, 2019 5 commits
    • Linus Torvalds's avatar
      Linux 5.0-rc4 · f17b5f06
      Linus Torvalds authored
      f17b5f06
    • Linus Torvalds's avatar
      Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 8a5f0605
      Linus Torvalds authored
      Pull x86 fixes from Thomas Gleixner:
       "A set of fixes for x86:
      
         - Fix the swapped outb() parameters in the KASLR code
      
         - Fix the PKEY handling at fork which missed to preserve the pkey
           state for the child. Comes with a test case to validate that.
      
         - Fix the entry stack handling for XEN PV to respect that XEN PV
           systems enter the function already on the current thread stack and
           not on the trampoline.
      
         - Fix kexec load failure caused by using a stale value when the
           kexec_buf structure is reused for subsequent allocations.
      
         - Fix a bogus sizeof() in the memory encryption code
      
         - Enforce PCI dependency for the Intel Low Power Subsystem
      
         - Enforce PCI_LOCKLESS_CONFIG when PCI is enabled"
      
      * 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
        x86/Kconfig: Select PCI_LOCKLESS_CONFIG if PCI is enabled
        x86/entry/64/compat: Fix stack switching for XEN PV
        x86/kexec: Fix a kexec_file_load() failure
        x86/mm/mem_encrypt: Fix erroneous sizeof()
        x86/selftests/pkeys: Fork() to check for state being preserved
        x86/pkeys: Properly copy pkey state at fork()
        x86/kaslr: Fix incorrect i8254 outb() parameters
        x86/intel/lpss: Make PCI dependency explicit
      8a5f0605
    • Linus Torvalds's avatar
      Merge branch 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 351e1aa6
      Linus Torvalds authored
      Pull x86 timer fixes from Thomas Gleixner:
       "Two commits which were missed to be sent during the merge window.
      
         - The TSC calibration fix turns out to be more urgent as recent
           Skylake-X systems seem to have massive trouble with calibration
           disturbance. This should go back into stable for that reason and it
           the risk of breakage is rather low.
      
         - Drop an unused define"
      
      * 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
        x86/hpet: Remove unused FSEC_PER_NSEC define
        x86/tsc: Make calibration refinement more robust
      351e1aa6
    • Linus Torvalds's avatar
      Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · f907bb4c
      Linus Torvalds authored
      Pull timer fix from Thomas Glexiner:
       "A single regression fix to address the unintended breakage of posix
        cpu timers.
      
        This is caused by a new sanity check in the common code, which fails
        for posix cpu timers under certain conditions because the posix cpu
        timer code never updates the variable which is checked"
      
      * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
        posix-cpu-timers: Unbreak timer rearming
      f907bb4c
    • Linus Torvalds's avatar
      Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 98810518
      Linus Torvalds authored
      Pull locking fixes from Thomas Gleixner:
       "A small series of fixes which all address possible missed wakeups:
      
         - Document and fix the wakeup ordering of wake_q
      
         - Add the missing barrier in rcuwait_wake_up(), which was documented
           in the comment but missing in the code
      
         - Fix the possible missed wakeups in the rwsem and futex code"
      
      * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
        locking/rwsem: Fix (possible) missed wakeup
        futex: Fix (possible) missed wakeup
        sched/wake_q: Fix wakeup ordering for wake_q
        sched/wake_q: Document wake_q_add()
        sched/wait: Fix rcuwait_wake_up() ordering
      98810518