1. 11 Jun, 2015 11 commits
    • Mike Snitzer's avatar
      dm thin: fail messages with EOPNOTSUPP when pool cannot handle messages · fd467696
      Mike Snitzer authored
      
      
      Use EOPNOTSUPP, rather than EINVAL, error code when user attempts to
      send the pool a message.  Otherwise usespace is led to believe the
      message failed due to invalid argument.
      Reported-by: default avatarZdenek Kabelac <zkabelac@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      fd467696
    • Joe Thornber's avatar
      dm thin: range discard support · 34fbcf62
      Joe Thornber authored
      
      
      Previously REQ_DISCARD bios have been split into block sized chunks
      before submission to the thin target.  There are a couple of issues with
      this:
      
       - If the block size is small, a large discard request can
         get broken up into a great many bios which is both slow and causes
         a lot of memory pressure.
      
       - The thin pool block size and the discard granularity for the
         underlying data device need to be compatible if we want to passdown
         the discard.
      
      This patch relaxes the block size granularity for thin devices.  It
      makes use of the recent range locking added to the bio_prison to
      quiesce a whole range of thin blocks before unmapping them.  Once a
      thin range has been unmapped the discard can then be passed down to
      the data device for those sub ranges where the data blocks are no
      longer used (ie. they weren't shared in the first place).
      
      This patch also doesn't make any apologies about open-coding portions
      of block core as a means to supporting async discard completions in the
      near-term -- if/when late bio splitting lands it'll all get cleaned up.
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      34fbcf62
    • Joe Thornber's avatar
      dm thin metadata: add dm_thin_remove_range() · 6550f075
      Joe Thornber authored
      
      
      Removes a range of blocks from the btree.
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      6550f075
    • Joe Thornber's avatar
      dm thin metadata: add dm_thin_find_mapped_range() · a5d895a9
      Joe Thornber authored
      
      
      Retrieve the next run of contiguously mapped blocks.  Useful for working
      out where to break up IO.
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      a5d895a9
    • Joe Thornber's avatar
      dm btree: add dm_btree_remove_leaves() · 4ec331c3
      Joe Thornber authored
      
      
      Removes a range of leaf values from the tree.
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      4ec331c3
    • Pekka Enberg's avatar
      dm stats: Use kvfree() in dm_kvfree() · 0f24b79b
      Pekka Enberg authored
      
      
      Use kvfree() instead of open-coding it.
      Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      0f24b79b
    • Joe Thornber's avatar
      dm cache: age and write back cache entries even without active IO · fba10109
      Joe Thornber authored
      
      
      The policy tick() method is normally called from interrupt context.
      Both the mq and smq policies do some bottom half work for the tick
      method in their map functions.  However if no IO is going through the
      cache, then that bottom half work doesn't occur.  With these policies
      this means recently hit entries do not age and do not get written
      back as early as we'd like.
      
      Fix this by introducing a new 'can_block' parameter to the tick()
      method.  When this is set the bottom half work occurs immediately.
      'can_block' is set when the tick method is called every second by the
      core target (not in interrupt context).
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      fba10109
    • Mike Snitzer's avatar
      dm cache: prefix all DMERR and DMINFO messages with cache device name · b61d9509
      Mike Snitzer authored
      
      
      Having the DM device name associated with the ERR or INFO message is
      very helpful.
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      b61d9509
    • Joe Thornber's avatar
      dm cache: add fail io mode and needs_check flag · 028ae9f7
      Joe Thornber authored
      
      
      If a cache metadata operation fails (e.g. transaction commit) the
      cache's metadata device will abort the current transaction, set a new
      needs_check flag, and the cache will transition to "read-only" mode.  If
      aborting the transaction or setting the needs_check flag fails the cache
      will transition to "fail-io" mode.
      
      Once needs_check is set the cache device will not be allowed to
      activate.  Activation requires write access to metadata.  Future work is
      needed to add proper support for running the cache in read-only mode.
      
      Once in fail-io mode the cache will report a status of "Fail".
      
      Also, add commit() wrapper that will disallow commits if in read_only or
      fail mode.
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      028ae9f7
    • Joe Thornber's avatar
      dm cache: wake the worker thread every time we free a migration object · 88bf5184
      Joe Thornber authored
      
      
      When the cache is idle, writeback work was only being issued every
      second.  With this change outstanding writebacks are streamed
      constantly.  This offers a writeback performance improvement.
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      88bf5184
    • Joe Thornber's avatar
      dm cache: add stochastic-multi-queue (smq) policy · 66a63635
      Joe Thornber authored
      
      
      The stochastic-multi-queue (smq) policy addresses some of the problems
      with the current multiqueue (mq) policy.
      
      Memory usage
      ------------
      
      The mq policy uses a lot of memory; 88 bytes per cache block on a 64
      bit machine.
      
      SMQ uses 28bit indexes to implement it's data structures rather than
      pointers.  It avoids storing an explicit hit count for each block.  It
      has a 'hotspot' queue rather than a pre cache which uses a quarter of
      the entries (each hotspot block covers a larger area than a single
      cache block).
      
      All these mean smq uses ~25bytes per cache block.  Still a lot of
      memory, but a substantial improvement nontheless.
      
      Level balancing
      ---------------
      
      MQ places entries in different levels of the multiqueue structures
      based on their hit count (~ln(hit count)).  This means the bottom
      levels generally have the most entries, and the top ones have very
      few.  Having unbalanced levels like this reduces the efficacy of the
      multiqueue.
      
      SMQ does not maintain a hit count, instead it swaps hit entries with
      the least recently used entry from the level above.  The over all
      ordering being a side effect of this stochastic process.  With this
      scheme we can decide how many entries occupy each multiqueue level,
      resulting in better promotion/demotion decisions.
      
      Adaptability
      ------------
      
      The MQ policy maintains a hit count for each cache block.  For a
      different block to get promoted to the cache it's hit count has to
      exceed the lowest currently in the cache.  This means it can take a
      long time for the cache to adapt between varying IO patterns.
      Periodically degrading the hit counts could help with this, but I
      haven't found a nice general solution.
      
      SMQ doesn't maintain hit counts, so a lot of this problem just goes
      away.  In addition it tracks performance of the hotspot queue, which
      is used to decide which blocks to promote.  If the hotspot queue is
      performing badly then it starts moving entries more quickly between
      levels.  This lets it adapt to new IO patterns very quickly.
      
      Performance
      -----------
      
      In my tests SMQ shows substantially better performance than MQ.  Once
      this matures a bit more I'm sure it'll become the default policy.
      Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      66a63635
  2. 29 May, 2015 25 commits
  3. 27 May, 2015 3 commits
    • Mike Snitzer's avatar
      dm: requeue from blk-mq dm_mq_queue_rq() using BLK_MQ_RQ_QUEUE_BUSY · 45714fbe
      Mike Snitzer authored
      
      
      Use BLK_MQ_RQ_QUEUE_BUSY to requeue a blk-mq request directly from the
      DM blk-mq device's .queue_rq.  This cleans up the previous convoluted
      handling of request requeueing that would return BLK_MQ_RQ_QUEUE_OK
      (even though it wasn't) and then run blk_mq_requeue_request() followed
      by blk_mq_kick_requeue_list().
      
      Also, document that DM blk-mq ontop of old request_fn devices cannot
      fail in clone_rq() since the clone request is preallocated as part of
      the pdu.
      Reported-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      45714fbe
    • Mike Snitzer's avatar
      dm mpath: fix leak of dm_mpath_io structure in blk-mq .queue_rq error path · 4c6dd53d
      Mike Snitzer authored
      Otherwise kmemleak reported:
      
      unreferenced object 0xffff88009b14e2b0 (size 16):
        comm "fio", pid 4274, jiffies 4294978034 (age 1253.210s)
        hex dump (first 16 bytes):
          40 12 f3 99 01 88 ff ff 00 10 00 00 00 00 00 00  @...............
        backtrace:
          [<ffffffff81600029>] kmemleak_alloc+0x49/0xb0
          [<ffffffff811679a8>] kmem_cache_alloc+0xf8/0x160
          [<ffffffff8111c950>] mempool_alloc_slab+0x10/0x20
          [<ffffffff8111cb37>] mempool_alloc+0x57/0x150
          [<ffffffffa04d2b61>] __multipath_map.isra.17+0xe1/0x220 [dm_multipath]
          [<ffffffffa04d2cb5>] multipath_clone_and_map+0x15/0x20 [dm_multipath]
          [<ffffffffa02889b5>] map_request.isra.39+0xd5/0x220 [dm_mod]
          [<ffffffffa028b0e4>] dm_mq_queue_rq+0x134/0x240 [dm_mod]
          [<ffffffff812cccb5>] __blk_mq_run_hw_queue+0x1d5/0x380
          [<ffffffff812ccaa5>] blk_mq_run_hw_queue+0xc5/0x100
          [<ffffffff812ce350>] blk_sq_make_request+0x240/0x300
          [<ffffffff812c0f30>] generic_make_request+0xc0/0x110
          [<ffffffff812c0ff2>] submit_bio+0x72/0x150
          [<ffffffff811c07cb>] do_blockdev_direct_IO+0x1f3b/0x2da0
          [<ffffffff811c166e>] __blockdev_direct_IO+0x3e/0x40
          [<ffffffff8120aa1a>] ext4_direct_IO+0x1aa/0x390
      
      Fixes: e5863d9a
      
       ("dm: allocate requests in target when stacking on blk-mq devices")
      Reported-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      Cc: stable@vger.kernel.org # 4.0+
      4c6dd53d
    • Junichi Nomura's avatar
      dm: fix NULL pointer when clone_and_map_rq returns !DM_MAPIO_REMAPPED · 3a140755
      Junichi Nomura authored
      When stacking request-based DM on blk_mq device, request cloning and
      remapping are done in a single call to target's clone_and_map_rq().
      The clone is allocated and valid only if clone_and_map_rq() returns
      DM_MAPIO_REMAPPED.
      
      The "IS_ERR(clone)" check in map_request() does not cover all the
      !DM_MAPIO_REMAPPED cases that are possible (E.g. if underlying devices
      are not ready or unavailable, clone_and_map_rq() may return
      DM_MAPIO_REQUEUE without ever having established an ERR_PTR).  Fix this
      by explicitly checking for a return that is not DM_MAPIO_REMAPPED in
      map_request().
      
      Without this fix, DM core may call setup_clone() for a NULL clone
      and oops like this:
      
         BUG: unable to handle kernel NULL pointer dereference at 0000000000000068
         IP: [<ffffffff81227525>] blk_rq_prep_clone+0x7d/0x137
         ...
         CPU: 2 PID: 5793 Comm: kdmwork-253:3 Not tainted 4.0.0-nm #1
         ...
         Call Trace:
          [<ffffffffa01d1c09>] map_tio_request+0xa9/0x258 [dm_mod]
          [<ffffffff81071de9>] kthread_worker_fn+0xfd/0x150
          [<ffffffff81071cec>] ? kthread_parkme+0x24/0x24
          [<ffffffff81071cec>] ? kthread_parkme+0x24/0x24
          [<ffffffff81071fdd>] kthread+0xe6/0xee
          [<ffffffff81093a59>] ? put_lock_stats+0xe/0x20
          [<ffffffff81071ef7>] ? __init_kthread_worker+0x5b/0x5b
          [<ffffffff814c2d98>] ret_from_fork+0x58/0x90
          [<ffffffff81071ef7>] ? __init_kthread_worker+0x5b/0x5b
      
      Fixes: e5863d9a
      
       ("dm: allocate requests in target when stacking on blk-mq devices")
      Reported-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
      Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      Cc: stable@vger.kernel.org # 4.0+
      3a140755
  4. 26 May, 2015 1 commit