Signed-off-by: NMike Snitzer <snitzer@redhat.com>

If a path selector has any use for a repeat_count it should be handled
locally and not depend on the dm-mpath core to be concerned with it.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Preparation for making __multipath_map() avoid taking the m->lock
spinlock -- in favor of using RCU locking.

repeat_count was primarily for bio-based DM multipath's benefit.  There
is really no need for it anymore now that DM multipath is request-based.
As such, repeat_count > 1 is no longer honored and a warning is
displayed if the user attempts to use a value > 1.  This is a temporary
change for the round-robin path-selector (as a later commit will restore
its support for repeat_count > 1).
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Signed-off-by: NMike Snitzer <snitzer@redhat.com>

There isn't any need to support both old .request_fn and blk-mq paths
in the blk-mq specific portion of __multipath_map().  Call
blk_mq_alloc_request() directly rather than use blk_get_request().

Similarly, call blk_mq_free_request(), rather than blk_put_request(), in
multipath_release_clone().
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Refactor and rename existing interfaces to be more specific and
self-documenting.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Allow the multipath target to avoid making small allocations for each
'struct dm_mpath_io' that is needed for each request.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Rename various methods to have either a "dm_old" or "dm_mq" prefix.
Improve code comments to assist with understanding the duality of code
that handles both "dm_old" and "dm_mq" cases.

It is no much easier to quickly look at the code and _know_ that a given
method is either 1) "dm_old" only 2) "dm_mq" only 3) common to both.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Remove all fiddley code that propped up this support for a blk-mq
request-queue ontop of all .request_fn devices.

Testing has proven this niche request-based dm-mq mode to be buggy, when
testing fault tolerance with DM multipath, and there is no point trying
to preserve it.

Should help improve efficiency of pure dm-mq code and make code
maintenance less delicate.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

DM multipath is the only dm-mq target.  But that aside, request-based DM
only supports tables with a single target that is immutable.  Leverage
this fact in dm_mq_queue_rq() by using the 'immutable_target' stored in
the mapped_device when the table was made active.  This saves the need
to even take the read-side of the SRCU via dm_{get,put}_live_table.

If the active DM table does not have an immutable target (e.g. "error"
target was swapped in) then fallback to the slow-path where the target
is looked up from the live table.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

In multipath_prepare_ioctl(),
  - pgpath is a path selected from available paths
  - m->queue_io is true if we cannot send a request immediately to
    paths, either because:
      * there is no available path
      * the path group needs activation (pg_init)
          - pg_init is not started
          - pg_init is still running
  - m->queue_if_no_path is true if the device is configured to queue
    I/O if there are no available paths

If !pgpath && !m->queue_if_no_path, the handler should return -EIO.
However in the course of refactoring the condition check has broken
and returns success in that case.  Since bdev points to the dm device
itself, dm_blk_ioctl() calls __blk_dev_driver_ioctl() for itself and
recurses until crash.

You could reproduce the problem like this:

  # dmsetup create mp --table '0 1024 multipath 0 0 0 0'
  # sg_inq /dev/mapper/mp
  <crash>
  [  172.648615] BUG: unable to handle kernel paging request at fffffffc81b10268
  [  172.662843] PGD 19dd067 PUD 0
  [  172.666269] Thread overran stack, or stack corrupted
  [  172.671808] Oops: 0000 [#1] SMP
  ...

Fix the condition check with some clarifications.

Fixes: e56f81e0 ("dm: refactor ioctl handling")
Signed-off-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

dm-mpath retries ioctl, when no path is readily available and the device
is configured to queue I/O in such a case. If you want to stop the retry
before multipathd decides to turn off queueing mode, you could send
signal for the process to exit from the loop.

However the check of fatal signal has not carried along when commit
6c182cd8 ("dm mpath: fix ioctl deadlock when no paths") moved the
loop from dm-mpath to dm core. As a result, we can't terminate such
a process in the retry loop.

Easy reproducer of the situation is:

  # dmsetup create mp --table '0 1024 multipath 0 0 0 0'
  # dmsetup message mp 0 'queue_if_no_path'
  # sg_inq /dev/mapper/mp

then you should be able to terminate sg_inq by pressing Ctrl+C.

Fixes: 6c182cd8 ("dm mpath: fix ioctl deadlock when no paths")
Signed-off-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

This adds support to pass through persistent reservation requests
similar to the existing ioctl handling, and with the same limitations,
e.g. devices may only have a single target attached.

This is mostly intended for multipathing.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

This moves the call to blkdev_ioctl and the argument checking to DM core
code, and only leaves a callout to find the block device to operate on
in the targets.  This simplifies the code and allows us to pass through
ioctl-like command using other methods in the next patch.

Also split out a helper around calling the prepare_ioctl method that
will be reused for persistent reservation handling.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

This reverts commit a1989b33.

That commit introduced a regression at least for the case of the SG_IO ioctl()
running without CAP_SYS_RAWIO capability (e.g., unprivileged users) when there
are no active paths: the ioctl() fails with the ENOTTY errno immediately rather
than blocking due to queue_if_no_path until a path becomes active, for example.

That case happens to be exercised by QEMU KVM guests with 'scsi-block' devices
(qemu "-device scsi-block" [1], libvirt "<disk type='block' device='lun'>" [2])
from multipath devices; which leads to SCSI/filesystem errors in such a guest.

More general scenarios can hit that regression too. The following demonstration
employs a SG_IO ioctl() with a standard SCSI INQUIRY command for this objective
(some output & user changes omitted for brevity and comments added for clarity).

Reverting that commit restores normal operation (queueing) in failing scenarios;
tested on linux-next (next-20151022).

1) Test-case is based on sg_simple0 [3] (just SG_IO; remove SG_GET_VERSION_NUM)

    $ cat sg_simple0.c
    ... see [3] ...
    $ sed '/SG_GET_VERSION_NUM/,/}/d' sg_simple0.c > sgio_inquiry.c
    $ gcc sgio_inquiry.c -o sgio_inquiry

2) The ioctl() works fine with active paths present.

    # multipath -l 85ag56
    85ag56 (...) dm-19 IBM     ,2145
    size=60G features='1 queue_if_no_path' hwhandler='0' wp=rw
    |-+- policy='service-time 0' prio=0 status=active
    | |- 8:0:11:0  sdz  65:144  active undef running
    | `- 9:0:9:0   sdbf 67:144  active undef running
    `-+- policy='service-time 0' prio=0 status=enabled
      |- 8:0:12:0  sdae 65:224  active undef running
      `- 9:0:12:0  sdbo 68:32   active undef running

    $ ./sgio_inquiry /dev/mapper/85ag56
    Some of the INQUIRY command's response:
        IBM       2145              0000
    INQUIRY duration=0 millisecs, resid=0

3) The ioctl() fails with ENOTTY errno with _no_ active paths present,
   for unprivileged users (rather than blocking due to queue_if_no_path).

    # for path in $(multipath -l 85ag56 | grep -o 'sd[a-z]\+'); \
          do multipathd -k"fail path $path"; done

    # multipath -l 85ag56
    85ag56 (...) dm-19 IBM     ,2145
    size=60G features='1 queue_if_no_path' hwhandler='0' wp=rw
    |-+- policy='service-time 0' prio=0 status=enabled
    | |- 8:0:11:0  sdz  65:144  failed undef running
    | `- 9:0:9:0   sdbf 67:144  failed undef running
    `-+- policy='service-time 0' prio=0 status=enabled
      |- 8:0:12:0  sdae 65:224  failed undef running
      `- 9:0:12:0  sdbo 68:32   failed undef running

    $ ./sgio_inquiry /dev/mapper/85ag56
    sg_simple0: Inquiry SG_IO ioctl error: Inappropriate ioctl for device

4) dmesg shows that scsi_verify_blk_ioctl() failed for SG_IO (0x2285);
   it returns -ENOIOCTLCMD, later replaced with -ENOTTY in vfs_ioctl().

    $ dmesg
    <...>
    [] device-mapper: multipath: Failing path 65:144.
    [] device-mapper: multipath: Failing path 67:144.
    [] device-mapper: multipath: Failing path 65:224.
    [] device-mapper: multipath: Failing path 68:32.
    [] sgio_inquiry: sending ioctl 2285 to a partition!

5) The ioctl() only works if the SYS_CAP_RAWIO capability is present
   (then queueing happens -- in this example, queue_if_no_path is set);
   this is due to a conditional check in scsi_verify_blk_ioctl().

    # capsh --drop=cap_sys_rawio -- -c './sgio_inquiry /dev/mapper/85ag56'
    sg_simple0: Inquiry SG_IO ioctl error: Inappropriate ioctl for device

    # ./sgio_inquiry /dev/mapper/85ag56 &
    [1] 72830

    # cat /proc/72830/stack
    [<c00000171c0df700>] 0xc00000171c0df700
    [<c000000000015934>] __switch_to+0x204/0x350
    [<c000000000152d4c>] msleep+0x5c/0x80
    [<c00000000077dfb0>] dm_blk_ioctl+0x70/0x170
    [<c000000000487c40>] blkdev_ioctl+0x2b0/0x9b0
    [<c0000000003128e4>] block_ioctl+0x64/0xd0
    [<c0000000002dd3b0>] do_vfs_ioctl+0x490/0x780
    [<c0000000002dd774>] SyS_ioctl+0xd4/0xf0
    [<c000000000009358>] system_call+0x38/0xd0

6) This is the function call chain exercised in this analysis:

SYSCALL_DEFINE3(ioctl, <...>) @ fs/ioctl.c
    -> do_vfs_ioctl()
        -> vfs_ioctl()
            ...
            error = filp->f_op->unlocked_ioctl(filp, cmd, arg);
            ...
                -> dm_blk_ioctl() @ drivers/md/dm.c
                    -> multipath_ioctl() @ drivers/md/dm-mpath.c
                        ...
                        (bdev = NULL, due to no active paths)
                        ...
                        if (!bdev || <...>) {
                            int err = scsi_verify_blk_ioctl(NULL, cmd);
                            if (err)
                                r = err;
                        }
                        ...
                            -> scsi_verify_blk_ioctl() @ block/scsi_ioctl.c
                                ...
                                if (bd && bd == bd->bd_contains) // not taken (bd = NULL)
                                    return 0;
                                ...
                                if (capable(CAP_SYS_RAWIO)) // not taken (unprivileged user)
                                    return 0;
                                ...
                                printk_ratelimited(KERN_WARNING
                                           "%s: sending ioctl %x to a partition!\n" <...>);

                                return -ENOIOCTLCMD;
                            <-
                        ...
                        return r ? : <...>
                    <-
            ...
            if (error == -ENOIOCTLCMD)
                error = -ENOTTY;
             out:
                return error;
            ...

Links:
[1] http://git.qemu.org/?p=qemu.git;a=commit;h=336a6915bc7089fb20fea4ba99972ad9a97c5f52
[2] https://libvirt.org/formatdomain.html#elementsDisks (see 'disk' -> 'device')
[3] http://tldp.org/HOWTO/SCSI-Generic-HOWTO/pexample.html (Revision 1.2, 2002-05-03)
Signed-off-by: NMauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

This way we can reused the same code any attachment method, not just those
requested from dm-mpath.

[jejb: fixup checkpatch error]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Acked-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJames Bottomley <JBottomley@Odin.com>

While allowing dm-mpath to attach device handlers is a functionality we need
for backwards compatibility reason there is no reason to reference count
them and detach them if dm-mpath stops using the device for some reason.

If the device handler works for the given device it can just stay attached,
and we can take the retain_hw_handler codepath.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NMike Snitzer <snitzer@redhat.com>
Acked-by: NHannes Reinecke <hare@Suse.de>
Signed-off-by: NJames Bottomley <JBottomley@Odin.com>

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: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 4.0+

dm_mq_queue_rq() is in atomic context so care must be taken to not
sleep -- as such GFP_ATOMIC is used for the md->bs bioset allocations
and dm-mpath's call to blk_get_request().  In the future the bioset
allocations will hopefully go away (by removing support for partial
completions of bios in a cloned request).

Also prepare for supporting DM blk-mq ontop of old-style request_fn
device(s) if a new dm-mod 'use_blk_mq' parameter is set.  The kthread
will still be used to queue work if blk-mq is used ontop of old-style
request_fn device(s).
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Commit e5863d9a ("dm: allocate requests in target when stacking on
blk-mq devices") served as the first step toward fully utilizing blk-mq
in request-based DM -- it enabled stacking an old-style (request_fn)
request_queue ontop of the underlying blk-mq device(s).  That first step
didn't improve performance of DM multipath ontop of fast blk-mq devices
(e.g. NVMe) because the top-level old-style request_queue was severely
limited by the queue_lock.

The second step offered here enables stacking a blk-mq request_queue
ontop of the underlying blk-mq device(s).  This unlocks significant
performance gains on fast blk-mq devices, Keith Busch tested on his NVMe
testbed and offered this really positive news:

 "Just providing a performance update. All my fio tests are getting
  roughly equal performance whether accessed through the raw block
  device or the multipath device mapper (~470k IOPS). I could only push
  ~20% of the raw iops through dm before this conversion, so this latest
  tree is looking really solid from a performance standpoint."
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Tested-by: NKeith Busch <keith.busch@intel.com>

There is no need for DM to export a wrapper around the already exported
blk_lld_busy().
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Currently the cleanup of all error cases are open-coded.  Introduce a
common exit path and labels.
Signed-off-by: NJohannes Thumshirn <morbidrsa@gmail.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

For blk-mq request-based DM the responsibility of allocating a cloned
request is transfered from DM core to the target type.  Doing so
enables the cloned request to be allocated from the appropriate
blk-mq request_queue's pool (only the DM target, e.g. multipath, can
know which block device to send a given cloned request to).

Care was taken to preserve compatibility with old-style block request
completion that requires request-based DM _not_ acquire the clone
request's queue lock in the completion path.  As such, there are now 2
different request-based DM target_type interfaces:
1) the original .map_rq() interface will continue to be used for
   non-blk-mq devices -- the preallocated clone request is passed in
   from DM core.
2) a new .clone_and_map_rq() and .release_clone_rq() will be used for
   blk-mq devices -- blk_get_request() and blk_put_request() are used
   respectively from these hooks.

dm_table_set_type() was updated to detect if the request-based target is
being stacked on blk-mq devices, if so DM_TYPE_MQ_REQUEST_BASED is set.
DM core disallows switching the DM table's type after it is set.  This
means that there is no mixing of non-blk-mq and blk-mq devices within
the same request-based DM table.

[This patch was started by Keith and later heavily modified by Mike]
Tested-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Switch to having request-based DM enqueue all prep'ed requests into work
processed by another thread.  This allows request-based DM to invoke
block APIs that assume interrupt enabled context (e.g. blk_get_request)
and is a prerequisite for adding blk-mq support to request-based DM.

The new kernel thread is only initialized for request-based DM devices.

multipath_map() is now always in irq enabled context so change multipath
spinlock (m->lock) locking to always disable interrupts.
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

'queue_io' is set so that IO is queued while paths are being
initialized.  Clear queue_io in __choose_pgpath if there are no valid
paths, since there are obviously no paths that can be initialized.
Otherwise IOs to the device will back up.
Signed-off-by: NBenjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

pg_ready() is not comprehensive in its logic and only serves to
obfuscate code.  Replace pg_ready() with the appropriate logic in
multipath_map().
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Commit e8099177 ("dm mpath: push back requests instead of queueing")
modified multipath_busy() to return true if !pg_ready().  pg_ready()
checks the current state of the multipath device and may return false
even if a new IO is needed to change the state.

Bart Van Assche reported that he had multipath IO lockup when he was
performing cable pull tests.  Analysis showed that the multipath
device had a single path group with both paths active, but that the
path group itself was not active.  During the multipath device state
transitions 'queue_io' got set but nothing could clear it.  Clearing
'queue_io' only happens in __choose_pgpath(), but it won't be called
if multipath_busy() returns true due to pg_ready() returning false
when 'queue_io' is set.

As such the !pg_ready() check in multipath_busy() is wrong because new
IO will not be sent to multipath target and the multipath state change
won't happen.  That results in multipath IO lockup.

The intent of multipath_busy() is to avoid unnecessary cycles of
dequeue + request_fn + requeue if it is known that the multipath
device will requeue.

Such "busy" situations would be:
  - path group is being activated
  - there is no path and the multipath is setup to requeue if no path

Fix multipath_busy() to return "busy" early only for these specific
situations.
Reported-by: NBart Van Assche <bvanassche@acm.org>
Tested-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v3.15

Add DM core support for disabling WRITE SAME on first failure to both
request-based and bio-based targets.  The need to disable WRITE SAME
stems from SCSI enabling it by default but then disabling it when it
fails.  When SCSI does this it returns "permanent target failure, do
not retry" using -EREMOTEIO.  Update DM core to only disable WRITE SAME
on failure if the returned error is -EREMOTEIO.

Commit f84cb8a4 ("dm mpath: disable WRITE SAME if it fails")
implemented multipath specific disabling of WRITE SAME if it fails.
However, as that commit detailed, the multipath-only solution doesn't go
far enough if bio-based DM targets are stacked ontop of the
request-based dm-multipath target (as is commonly done using dm-linear
to support partitions on multipath devices, via kpartx).
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Acked-by: NMartin K. Petersen <martin.petersen@oracle.com>
Tested-by: NAlex Chen <alex.chen@huawei.com>

lockdep complains about a circular locking.  And indeed, we need to
release the lock before calling dm_table_run_md_queue_async().

As such, commit 4cdd2ad7 ("dm mpath: fix lock order inconsistency in
multipath_ioctl") must also be reverted in addition to fixing the
lock order in the other dm_table_run_md_queue_async() callers.
Reported-by: NBart van Assche <bvanassche@acm.org>
Tested-by: NBart van Assche <bvanassche@acm.org>
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Commit 3e9f1be1 ("dm mpath: remove process_queued_ios()") did not
consistently take the multipath device's spinlock (m->lock) before
calling dm_table_run_md_queue_async() -- which takes the q->queue_lock.

Found with code inspection using hint from reported lockdep warning.
Reported-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

The warning message "Unrecognised multipath message received" is
displayed in two different situations in multipath_message(): when the
number of arguments passed is invalid and when the string passed in
argv[0] is not recognized.

Make it easier to identify where the problem is by making these warnings
more specific with additional context for each case.
Signed-off-by: NJose Castillo <jcastillo@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

activate_path() is run without a lock, so the path might be
set to failed before activate_path() had a chance to run.
This patch add a check for ->active in activate_path() to
avoid unnecessary overhead by calling functions which are known
to be failing.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Return early for case when no path exists, and when the
pathgroup isn't ready. This eliminates the need for
extra nesting for the the common case.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NHannes Reinecke <hare@suse.de>

multipath_map() is now just a wrapper around map_io(), so we
can rename map_io() to multipath_map().
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Reviewed-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>

When multipath needs to requeue I/O in the block layer the per-request
context shouldn't be allocated, as it will be freed immediately
afterwards anyway.  Avoiding this memory allocation will reduce memory
pressure during requeuing.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Reviewed-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>

process_queued_ios() has served 3 functions:
  1) select pg and pgpath if none is selected
  2) start pg_init if requested
  3) dispatch queued IOs when pg is ready

Basically, a call to queue_work(process_queued_ios) can be replaced by
dm_table_run_md_queue_async(), which runs request queue and ends up
calling map_io(), which does 1), 2) and 3).

Exception is when !pg_ready() (which means either pg_init is running or
requested), then multipath_busy() prevents map_io() being called from
request_fn.

If pg_init is running, it should be ok as long as pg_init_done() does
the right thing when pg_init is completed, I.e.: restart pg_init if
!pg_ready() or call dm_table_run_md_queue_async() to kick map_io().

If pg_init is requested, we have to make sure the request is detected
and pg_init will be started.  pg_init is requested in 3 places:
  a) __choose_pgpath() in map_io()
  b) __choose_pgpath() in multipath_ioctl()
  c) pg_init retry in pg_init_done()
a) is ok because map_io() calls __pg_init_all_paths(), which does 2).
b) needs a call to __pg_init_all_paths(), which does 2).
c) needs a call to __pg_init_all_paths(), which does 2).

So this patch removes process_queued_ios() and ensures that
__pg_init_all_paths() is called at the appropriate locations.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Reviewed-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>

There is no reason why multipath needs to queue requests internally for
queue_if_no_path or pg_init; we should rather push them back onto the
request queue.

And while we're at it we can simplify the conditional statement in
map_io() to make it easier to read.

Since mpath no longer does internal queuing of I/O the table info no
longer emits the internal queue_size.  Instead it displays 1 if queuing
is being used or 0 if it is not.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Reviewed-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>

This patch moves condition checks as a preparation of following
patches and has no effect on behaviour.
process_queued_ios() is the only caller of __pg_init_all_paths()
and 2 condition checks are moved from outside to inside without
side effects.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Reviewed-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>

An invalid ioctl will never be valid, irrespective of whether multipath
has active paths or not.  So for invalid ioctls we do not have to wait
for multipath to activate any paths, but can rather return an error
code immediately.  This fix resolves numerous instances of:

 udevd[]: worker [] unexpectedly returned with status 0x0100

that have been seen during testing.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

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: NHannes Reinecke <hare@suse.de>
[patch header edited for clarity and typos by Mike Snitzer]
Signed-off-by: NMike Snitzer <snitzer@redhat.com>