This patch converts dm-multipath target to request-based from bio-based.

Basically, the patch just converts the I/O unit from struct bio
to struct request.
In the course of the conversion, it also changes the I/O queueing
mechanism.  The change in the I/O queueing is described in details
as follows.

I/O queueing mechanism change
-----------------------------
In I/O submission, map_io(), there is no mechanism change from
bio-based, since the clone request is ready for retry as it is.
However, in I/O complition, do_end_io(), there is a mechanism change
from bio-based, since the clone request is not ready for retry.

In do_end_io() of bio-based, the clone bio has all needed memory
for resubmission.  So the target driver can queue it and resubmit
it later without memory allocations.
The mechanism has almost no overhead.

On the other hand, in do_end_io() of request-based, the clone request
doesn't have clone bios, so the target driver can't resubmit it
as it is.  To resubmit the clone request, memory allocation for
clone bios is needed, and it takes some overheads.
To avoid the overheads just for queueing, the target driver doesn't
queue the clone request inside itself.
Instead, the target driver asks dm core for queueing and remapping
the original request of the clone request, since the overhead for
queueing is just a freeing memory for the clone request.

As a result, the target driver doesn't need to record/restore
the information of the original request for resubmitting
the clone request.  So dm_bio_details in dm_mpath_io is removed.

multipath_busy()
---------------------
The target driver returns "busy", only when the following case:
  o The target driver will map I/Os, if map() function is called
  and
  o The mapped I/Os will wait on underlying device's queue due to
    their congestions, if map() function is called now.

In other cases, the target driver doesn't return "busy".
Otherwise, dm core will keep the I/Os and the target driver can't
do what it wants.
(e.g. the target driver can't map I/Os now, so wants to kill I/Os.)
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

This patch disables interrupt when taking map_lock to avoid
lockdep warnings in request-based dm.

request-based dm takes map_lock after taking queue_lock with
disabling interrupt:
  spin_lock_irqsave(queue_lock)
  q->request_fn() == dm_request_fn()
    => dm_get_table()
         => read_lock(map_lock)
while queue_lock could be (but isn't) taken in interrupt context.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Acked-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Request-based dm doesn't have barrier support yet.
So we need to set QUEUE_ORDERED_DRAIN only for bio-based dm.
Since the device type is decided at the first table loading time,
the flag set is deferred until then.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

This patch enables request-based dm.

o Request-based dm and bio-based dm coexist, since there are
  some target drivers which are more fitting to bio-based dm.
  Also, there are other bio-based devices in the kernel
  (e.g. md, loop).
  Since bio-based device can't receive struct request,
  there are some limitations on device stacking between
  bio-based and request-based.

                     type of underlying device
                   bio-based      request-based
   ----------------------------------------------
    bio-based         OK                OK
    request-based     --                OK

  The device type is recognized by the queue flag in the kernel,
  so dm follows that.

o The type of a dm device is decided at the first table binding time.
  Once the type of a dm device is decided, the type can't be changed.

o Mempool allocations are deferred to at the table loading time, since
  mempools for request-based dm are different from those for bio-based
  dm and needed mempool type is fixed by the type of table.

o Currently, request-based dm supports only tables that have a single
  target.  To support multiple targets, we need to support request
  splitting or prevent bio/request from spanning multiple targets.
  The former needs lots of changes in the block layer, and the latter
  needs that all target drivers support merge() function.
  Both will take a time.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

This patch adds core functions for request-based dm.

When struct mapped device (md) is initialized, md->queue has
an I/O scheduler and the following functions are used for
request-based dm as the queue functions:
    make_request_fn: dm_make_request()
    pref_fn:         dm_prep_fn()
    request_fn:      dm_request_fn()
    softirq_done_fn: dm_softirq_done()
    lld_busy_fn:     dm_lld_busy()
Actual initializations are done in another patch (PATCH 2).

Below is a brief summary of how request-based dm behaves, including:
  - making request from bio
  - cloning, mapping and dispatching request
  - completing request and bio
  - suspending md
  - resuming md

  bio to request
  ==============
  md->queue->make_request_fn() (dm_make_request()) calls __make_request()
  for a bio submitted to the md.
  Then, the bio is kept in the queue as a new request or merged into
  another request in the queue if possible.

  Cloning and Mapping
  ===================
  Cloning and mapping are done in md->queue->request_fn() (dm_request_fn()),
  when requests are dispatched after they are sorted by the I/O scheduler.

  dm_request_fn() checks busy state of underlying devices using
  target's busy() function and stops dispatching requests to keep them
  on the dm device's queue if busy.
  It helps better I/O merging, since no merge is done for a request
  once it is dispatched to underlying devices.

  Actual cloning and mapping are done in dm_prep_fn() and map_request()
  called from dm_request_fn().
  dm_prep_fn() clones not only request but also bios of the request
  so that dm can hold bio completion in error cases and prevent
  the bio submitter from noticing the error.
  (See the "Completion" section below for details.)

  After the cloning, the clone is mapped by target's map_rq() function
    and inserted to underlying device's queue using
    blk_insert_cloned_request().

  Completion
  ==========
  Request completion can be hooked by rq->end_io(), but then, all bios
  in the request will have been completed even error cases, and the bio
  submitter will have noticed the error.
  To prevent the bio completion in error cases, request-based dm clones
  both bio and request and hooks both bio->bi_end_io() and rq->end_io():
      bio->bi_end_io(): end_clone_bio()
      rq->end_io():     end_clone_request()

  Summary of the request completion flow is below:
  blk_end_request() for a clone request
    => blk_update_request()
       => bio->bi_end_io() == end_clone_bio() for each clone bio
          => Free the clone bio
          => Success: Complete the original bio (blk_update_request())
             Error:   Don't complete the original bio
    => blk_finish_request()
       => rq->end_io() == end_clone_request()
          => blk_complete_request()
             => dm_softirq_done()
                => Free the clone request
                => Success: Complete the original request (blk_end_request())
                   Error:   Requeue the original request

  end_clone_bio() completes the original request on the size of
  the original bio in successful cases.
  Even if all bios in the original request are completed by that
  completion, the original request must not be completed yet to keep
  the ordering of request completion for the stacking.
  So end_clone_bio() uses blk_update_request() instead of
  blk_end_request().
  In error cases, end_clone_bio() doesn't complete the original bio.
  It just frees the cloned bio and gives over the error handling to
  end_clone_request().

  end_clone_request(), which is called with queue lock held, completes
  the clone request and the original request in a softirq context
  (dm_softirq_done()), which has no queue lock, to avoid a deadlock
  issue on submission of another request during the completion:
      - The submitted request may be mapped to the same device
      - Request submission requires queue lock, but the queue lock
        has been held by itself and it doesn't know that

  The clone request has no clone bio when dm_softirq_done() is called.
  So target drivers can't resubmit it again even error cases.
  Instead, they can ask dm core for requeueing and remapping
  the original request in that cases.

  suspend
  =======
  Request-based dm uses stopping md->queue as suspend of the md.
  For noflush suspend, just stops md->queue.

  For flush suspend, inserts a marker request to the tail of md->queue.
  And dispatches all requests in md->queue until the marker comes to
  the front of md->queue.  Then, stops dispatching request and waits
  for the all dispatched requests to complete.
  After that, completes the marker request, stops md->queue and
  wake up the waiter on the suspend queue, md->wait.

  resume
  ======
  Starts md->queue.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

This patch contains a device-mapper mirror log module that forwards
requests to userspace for processing.

The structures used for communication between kernel and userspace are
located in include/linux/dm-log-userspace.h.  Due to the frequency,
diversity, and 2-way communication nature of the exchanges between
kernel and userspace, 'connector' was chosen as the interface for
communication.

The first log implementations written in userspace - "clustered-disk"
and "clustered-core" - support clustered shared storage.   A userspace
daemon (in the LVM2 source code repository) uses openAIS/corosync to
process requests in an ordered fashion with the rest of the nodes in the
cluster so as to prevent log state corruption.  Other implementations
with no association to LVM or openAIS/corosync, are certainly possible.

(Imagine if two machines are writing to the same region of a mirror.
They would both mark the region dirty, but you need a cluster-aware
entity that can handle properly marking the region clean when they are
done.  Otherwise, you might clear the region when the first machine is
done, not the second.)
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Currently, device-mapper maintains a separate instance of 'struct
queue_limits' for each table of each device.  When the configuration of
a device is to be changed, first its table is loaded and this structure
is populated, then the device is 'resumed' and the calculated
queue_limits are applied.

This places restrictions on how userspace may process related devices,
where it is often advantageous to 'load' tables for several devices
at once before 'resuming' them together.  As the new queue_limits
only take effect after the 'resume', if they are changing and one
device uses another, the latter must be 'resumed' before the former
may be 'loaded'.

This patch moves the calculation of these queue_limits out of
the 'load' operation into 'resume'.  Since we are no longer
pre-calculating this struct, we no longer need to maintain copies
within our dm structs.

dm_set_device_limits() now passes the 'start' of the device's
data area (aka pe_start) as the 'offset' to blk_stack_limits().

init_valid_queue_limits() is replaced by blk_set_default_limits().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: martin.petersen@oracle.com
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

create_log_context() must use the logical_block_size from the log disk,
where the I/O happens, not the target's logical_block_size.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Add .iterate_devices to 'struct target_type' to allow a function to be
called for all devices in a DM target.  Implemented it for all targets
except those in dm-snap.c (origin and snapshot).

(The raid1 version number jumps to 1.12 because we originally reserved
1.1 to 1.11 for 'block_on_error' but ended up using 'handle_errors'
instead.)
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: martin.petersen@oracle.com

Copy the table's queue_limits to the DM device's request_queue.  This
properly initializes the queue's topology limits and also avoids having
to track the evolution of 'struct queue_limits' in
dm_table_set_restrictions()

Also fixes a bug that was introduced in dm_table_set_restrictions() via
commit ae03bf63.  In addition to
establishing 'bounce_pfn' in the queue's limits blk_queue_bounce_limit()
also performs an allocation to setup the ISA DMA pool.  This allocation
resulted in "sleeping function called from invalid context" when called
from dm_table_set_restrictions().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Use blk_stack_limits() to stack block limits (including topology) rather
than duplicate the equivalent within Device Mapper.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Impose necessary and sufficient conditions on a devices's table such
that any incoming bio which respects its logical_block_size can be
processed successfully.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Ensure I/O is aligned to the logical block size of target devices.

Rename check_device_area() to device_area_is_valid() for clarity and
establish the device limits including the logical block size prior to
calling it.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Add support for passing a 32 bit "cookie" into the kernel with the
DM_SUSPEND, DM_DEV_RENAME and DM_DEV_REMOVE ioctls.  The (unsigned)
value of this cookie is returned to userspace alongside the uevents
issued by these ioctls in the variable DM_COOKIE.

This means the userspace process issuing these ioctls can be notified
by udev after udev has completed any actions triggered.

To minimise the interface extension, we pass the cookie into the
kernel in the event_nr field which is otherwise unused when calling
these ioctls.  Incrementing the version number allows userspace to
determine in advance whether or not the kernel supports the cookie.
If the kernel does support this but userspace does not, there should
be no impact as the new variable will just get ignored.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Add a file named 'suspended' to each device-mapper device directory in
sysfs.  It holds the value 1 while the device is suspended.  Otherwise
it holds 0.
Signed-off-by: Peter Rajnoha <prajnoha@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Report any devices forgotten to be freed before a table is destroyed.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

This patch adds a service time oriented dynamic load balancer,
dm-service-time, which selects the path with the shortest estimated
service time for the incoming I/O.
The service time is estimated by dividing the in-flight I/O size
by a performance value of each path.

The performance value can be given as a table argument at the table
loading time.  If no performance value is given, all paths are
considered equal.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

This patch adds a dynamic load balancer, dm-queue-length, which
balances the number of in-flight I/Os across the paths.

The code is based on the patch posted by Stefan Bader:
https://www.redhat.com/archives/dm-devel/2005-October/msg00050.htmlSigned-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

This patch makes two additions to the dm path selector interface for
dynamic load balancers:
  o a new hook, start_io()
  o a new parameter 'nr_bytes' to select_path()/start_io()/end_io()
    to pass the size of the I/O

start_io() is called when a target driver actually submits I/O
to the selected path.
Path selectors can use it to start accounting of the I/O.
(e.g. counting the number of in-flight I/Os.)
The start_io hook is based on the patch posted by Stefan Bader:
https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html

nr_bytes, the size of the I/O, is so path selectors can take the
size of the I/O into account when deciding which path to use.
dm-service-time uses it to estimate service time, for example.
(Added the nr_bytes member to dm_mpath_io instead of using existing
 details.bi_size, since request-based dm patch deletes it.)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Send barrier requests when updating the exception area.

Exception area updates need to be ordered w.r.t. data writes, so that
the writes are not reordered in hardware disk cache.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

If -EOPNOTSUPP was returned and the request was a barrier request, retry it
without barrier.

Retry all regions for now. Barriers are submitted only for one-region requests,
so it doesn't matter.  (In the future, retries can be limited to the actual
regions that failed.)
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Add another field, eopnotsupp_bits. It is subset of error_bits, representing
regions that returned -EOPNOTSUPP.  (The bit is set in both error_bits and
eopnotsupp_bits).

This value will be used in further patches.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Flush support for dm-snapshot target.

This patch just forwards the flush request to either the origin or the snapshot
device.  (It doesn't flush exception store metadata.)
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Flush support for dm-multipath target.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Flush support for dm-delay target.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Flush support for dm-crypt target.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Flush support for the stripe target.

This sets ti->num_flush_requests to the number of stripes and
remaps individual flush requests to the appropriate stripe devices.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Flush support for the linear target.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Pass empty barrier flushes to the targets in dm_flush().
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Move repeated dm_target_io initialisation inside alloc_tio().
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Introduce num_flush_requests for a target to set to say how many flush
instructions (empty barriers) it wants to receive.  These are sent by
__clone_and_map_empty_barrier with map_info->flush_request going from 0
to (num_flush_requests - 1).

Old targets without flush support won't receive any flush requests.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Remove the check that the size of the cloned bio is not zero because a
subsequent patch needs to send zero-sized barriers down this path.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

If the underlying device doesn't support barriers and dm receives a
barrier, it waits until all requests on that device drain so it no
longer needs to report -EOPNOTSUPP to the caller.

This patch deals with the confusing situation when moving a volume from
one physical device to another triggers an EOPNOTSUPP on a volume that
didn't report it before.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

With the following patches, more than one error can occur during
processing.  Change md->barrier_error so that only the first one is
recorded and returned to the caller.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

If barrier request was returned with DM_ENDIO_REQUEUE,
requeue it in dm_wq_work instead of dec_pending.

This allows us to correctly handle a situation when some targets
are asking for a requeue and other targets signal an error.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Make dm_flush return void.

The first error during flush is stored in md->barrier_error instead.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Fix a potential deadlock when creating multiple snapshots by holding a
reference to struct block_device for the whole lifecycle of every dm
device instead of obtaining it independently at each point it is needed.

bdget_disk() was called while the device was being suspended, in
dm_suspend().  However there could be other devices already suspended,
for example when creating additional snapshots of a device. bdget_disk()
can wait for IO and allocate memory resulting in waiting for the
already-suspended device - deadlock.

This patch changes the code so that it gets the reference to struct
block_device when struct mapped_device is allocated and initialized in
alloc_dev() where it is always OK to allocate memory or wait for I/O.
It drops the reference when it is destroyed in free_dev().  Thus there
is no call to bdget_disk() while any device is suspended.

Previously unlock_fs() was called only if bdev was held.  Now it is
called unconditionally, but the superfluous calls are harmless because
it returns immediately if the filesystem was not previously frozen.

This patch also now allows the device size to be changed in a
noflush suspend because the bdev is held.  This has no adverse effect.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Rename suspended_bdev to bdev.

This patch doesn't change any functionality, just renames the variable.
In the next patch, the variable will be used even for non-suspended device.

(Pre-requisite for the per-target barrier support patches.)
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

When snapshots are created using 'p' instead of 'P' as the
exception store type, the device-mapper table loading fails.

This patch makes the code case insensitive as intended and fixes some
regressions reported with device-mapper snapshots.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Use i_size_read() instead of reading i_size.

If someone changes the size of the device simultaneously, i_size_read
is guaranteed to return a valid value (either the old one or the new one).

i_size can return some intermediate invalid value (on 32-bit computers
with 64-bit i_size, the reads to both halves of i_size can be interleaved
with updates to i_size, resulting in garbage being returned).

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>