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  1. 11 Nov, 2013 2 commits
    • Joe Thornber's avatar
      dm cache: add passthrough mode · 2ee57d58
      Joe Thornber authored 
      "Passthrough" is a dm-cache operating mode (like writethrough or
writeback) which is intended to be used when the cache contents are not
known to be coherent with the origin device.  It behaves as follows:

* All reads are served from the origin device (all reads miss the cache)
* All writes are forwarded to the origin device; additionally, write
  hits cause cache block invalidates

This mode decouples cache coherency checks from cache device creation,
largely to avoid having to perform coherency checks while booting.  Boot
scripts can create cache devices in passthrough mode and put them into
service (mount cached filesystems, for example) without having to worry
about coherency.  Coherency that exists is maintained, although the
cache will gradually cool as writes take place.

Later, applications can perform coherency checks, the nature of which
will depend on the type of the underlying storage.  If coherency can be
verified, the cache device can be transitioned to writethrough or
writeback mode while still warm; otherwise, the cache contents can be
discarded prior to transitioning to the desired operating mode.
Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarHeinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: default avatarMorgan Mears <Morgan.Mears@netapp.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      2ee57d58
    • Joe Thornber's avatar
      dm cache: cache shrinking support · f494a9c6
      Joe Thornber authored 
      Allow a cache to shrink if the blocks being removed from the cache are
not dirty.
Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      f494a9c6
  3. 09 Nov, 2013 21 commits
  5. 05 Nov, 2013 2 commits
    • Joe Thornber's avatar
      dm array: fix bug in growing array · 9c1d4de5
      Joe Thornber authored 
      Entries would be lost if the old tail block was partially filled.
Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.9+
      9c1d4de5
    • Hannes Reinecke's avatar
      dm mpath: requeue I/O during pg_init · b63349a7
      Hannes Reinecke authored 
      When pg_init is running no I/O can be submitted to the underlying
devices, as the path priority etc might change.  When using queue_io for
this, requests will be piling up within multipath as the block I/O
scheduler just sees a _very fast_ device.  All of this queued I/O has to
be resubmitted from within multipathing once pg_init is done.

This approach has the problem that it's virtually impossible to
abort I/O when pg_init is running, and we're adding heavy load
to the devices after pg_init since all of the queued I/O needs to be
resubmitted _before_ any requests can be pulled off of the request queue
and normal operation continues.

This patch will requeue the I/O that triggers the pg_init call, and
return 'busy' when pg_init is in progress.  With these changes the block
I/O scheduler will stop submitting I/O during pg_init, resulting in a
quicker path switch and less I/O pressure (and memory consumption) after
pg_init.
Signed-off-by: default avatarHannes Reinecke <hare@suse.de>
[patch header edited for clarity and typos by Mike Snitzer]
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      b63349a7
  7. 01 Nov, 2013 1 commit
    • Shiva Krishna Merla's avatar
      dm mpath: fix race condition between multipath_dtr and pg_init_done · 954a73d5
      Shiva Krishna Merla authored 
      Whenever multipath_dtr() is happening we must prevent queueing any
further path activation work.  Implement this by adding a new
'pg_init_disabled' flag to the multipath structure that denotes future
path activation work should be skipped if it is set.  By disabling
pg_init and then re-enabling in flush_multipath_work() we also avoid the
potential for pg_init to be initiated while suspending an mpath device.

Without this patch a race condition exists that may result in a kernel
panic:

1) If after pg_init_done() decrements pg_init_in_progress to 0, a call
   to wait_for_pg_init_completion() assumes there are no more pending path
   management commands.
2) If pg_init_required is set by pg_init_done(), due to retryable
   mode_select errors, then process_queued_ios() will again queue the
   path activation work.
3) If free_multipath() completes before activate_path() work is called a
   NULL pointer dereference like the following can be seen when
   accessing members of the recently destructed multipath:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000090
RIP: 0010:[<ffffffffa003db1b>]  [<ffffffffa003db1b>] activate_path+0x1b/0x30 [dm_multipath]
[<ffffffff81090ac0>] worker_thread+0x170/0x2a0
[<ffffffff81096c80>] ? autoremove_wake_function+0x0/0x40

[switch to disabling pg_init in flush_multipath_work & header edits by Mike Snitzer]
Signed-off-by: default avatarShiva Krishna Merla <shivakrishna.merla@netapp.com>
Reviewed-by: default avatarKrishnasamy Somasundaram <somasundaram.krishnasamy@netapp.com>
Tested-by: default avatarSpeagle Andy <Andy.Speagle@netapp.com>
Acked-by: default avatarJunichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
      954a73d5
  9. 31 Oct, 2013 1 commit
  11. 13 Oct, 2013 13 commits
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