Makes dm_get_md() and dm_get_from_kobject() have similar code.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

The following BUG_ON was hit when testing repeat creation and removal of
DM devices:

    kernel BUG at drivers/md/dm.c:2919!
    CPU: 7 PID: 750 Comm: systemd-udevd Not tainted 4.1.44
    Call Trace:
     [<ffffffff81649e8b>] dm_get_from_kobject+0x34/0x3a
     [<ffffffff81650ef1>] dm_attr_show+0x2b/0x5e
     [<ffffffff817b46d1>] ? mutex_lock+0x26/0x44
     [<ffffffff811df7f5>] sysfs_kf_seq_show+0x83/0xcf
     [<ffffffff811de257>] kernfs_seq_show+0x23/0x25
     [<ffffffff81199118>] seq_read+0x16f/0x325
     [<ffffffff811de994>] kernfs_fop_read+0x3a/0x13f
     [<ffffffff8117b625>] __vfs_read+0x26/0x9d
     [<ffffffff8130eb59>] ? security_file_permission+0x3c/0x44
     [<ffffffff8117bdb8>] ? rw_verify_area+0x83/0xd9
     [<ffffffff8117be9d>] vfs_read+0x8f/0xcf
     [<ffffffff81193e34>] ? __fdget_pos+0x12/0x41
     [<ffffffff8117c686>] SyS_read+0x4b/0x76
     [<ffffffff817b606e>] system_call_fastpath+0x12/0x71

The bug can be easily triggered, if an extra delay (e.g. 10ms) is added
between the test of DMF_FREEING & DMF_DELETING and dm_get() in
dm_get_from_kobject().

To fix it, we need to ensure the test of DMF_FREEING & DMF_DELETING and
dm_get() are done in an atomic way, so _minor_lock is used.

The other callers of dm_get() have also been checked to be OK: some
callers invoke dm_get() under _minor_lock, some callers invoke it under
_hash_lock, and dm_start_request() invoke it after increasing
md->open_count.

Cc: stable@vger.kernel.org
Signed-off-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

The structure srcu_struct can be very big, its size is proportional to the
value CONFIG_NR_CPUS. The Fedora kernel has CONFIG_NR_CPUS 8192, the field
io_barrier in the struct mapped_device has 84kB in the debugging kernel
and 50kB in the non-debugging kernel. The large size may result in failure
of the function kzalloc_node.

In order to avoid the allocation failure, we use the function
kvzalloc_node, this function falls back to vmalloc if a large contiguous
chunk of memory is not available. This patch also moves the field
io_barrier to the last position of struct mapped_device - the reason is
that on many processor architectures, short memory offsets result in
smaller code than long memory offsets - on x86-64 it reduces code size by
320 bytes.

Note to stable kernel maintainers - the kernels 4.11 and older don't have
the function kvzalloc_node, you can use the function vzalloc_node instead.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

Please do not apply this to mainline directly, instead please re-run the
coccinelle script shown below and apply its output.

For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't harmful, and changing them results in
churn.

However, for some features, the read/write distinction is critical to
correct operation. To distinguish these cases, separate read/write
accessors must be used. This patch migrates (most) remaining
ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
coccinelle script:

----
// Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
// WRITE_ONCE()

// $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch

virtual patch

@ depends on patch @
expression E1, E2;
@@

- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)

@ depends on patch @
expression E;
@@

- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

atomic_t variables are currently used to implement reference
counters with the following properties:
 - counter is initialized to 1 using atomic_set()
 - a resource is freed upon counter reaching zero
 - once counter reaches zero, its further
   increments aren't allowed
 - counter schema uses basic atomic operations
   (set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable table_device.count is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NDavid Windsor <dwindsor@gmail.com>
Reviewed-by: NHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: NElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

We already have a queue_is_rq_based helper to check if a request_queue
is request based, so we can remove the flag for it.
Acked-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The size of struct dm_name_list is different on 32-bit and 64-bit
kernels (so "(nl + 1)" differs between 32-bit and 64-bit kernels).

This mismatch caused some harmless difference in padding when using 32-bit
or 64-bit kernel. Commit 23d70c5e ("dm ioctl: report event number in
DM_LIST_DEVICES") added reporting event number in the output of
DM_LIST_DEVICES_CMD. This difference in padding makes it impossible for
userspace to determine the location of the event number (the location
would be different when running on 32-bit and 64-bit kernels).

Fix the padding by using offsetof(struct dm_name_list, name) instead of
sizeof(struct dm_name_list) to determine the location of entries.

Also, the ioctl version number is incremented to 37 so that userspace
can use the version number to determine that the event number is present
and correctly located.

In addition, a global event is now raised when a DM device is created,
removed, renamed or when table is swapped, so that the user can monitor
for device changes.
Reported-by: NEugene Syromiatnikov <esyr@redhat.com>
Fixes: 23d70c5e ("dm ioctl: report event number in DM_LIST_DEVICES")
Cc: stable@vger.kernel.org # 4.13
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Commit abebfbe2 ("dm: add ->flush() dax operation support") is
buggy. A DM device may be composed of multiple underlying devices and
all of them need to be flushed. That commit just routes the flush
request to the first device and ignores the other devices.

It could be fixed by adding more complex logic to the device mapper. But
there is only one implementation of the method pmem_dax_ops->flush - that
is pmem_dax_flush() - and it calls arch_wb_cache_pmem(). Consequently, we
don't need the pmem_dax_ops->flush abstraction at all, we can call
arch_wb_cache_pmem() directly from dax_flush() because dax_dev->ops->flush
can't ever reach anything different from arch_wb_cache_pmem().

It should be also pointed out that for some uses of persistent memory it
is needed to flush only a very small amount of data (such as 1 cacheline),
and it would be overkill if we go through that device mapper machinery for
a single flushed cache line.

Fix this by removing the pmem_dax_ops->flush abstraction and call
arch_wb_cache_pmem() directly from dax_flush(). Also, remove the device
mapper code that forwards the flushes.

Fixes: abebfbe2 ("dm: add ->flush() dax operation support")
Cc: stable@vger.kernel.org
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Using the same rate limiting state for different kinds of messages
is wrong because this can cause a high frequency message to suppress
a report of a low frequency message. Hence use a unique rate limiting
state per message type.

Fixes: 71a16736 ("dm: use local printk ratelimit")
Cc: stable@vger.kernel.org
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Detected by sparse.

Fixes: 4e4cbee9 ("block: switch bios to blk_status_t")
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NLaurence Oberman <loberman@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

This way we don't need a block_device structure to submit I/O.  The
block_device has different life time rules from the gendisk and
request_queue and is usually only available when the block device node
is open.  Other callers need to explicitly create one (e.g. the lightnvm
passthrough code, or the new nvme multipathing code).

For the actual I/O path all that we need is the gendisk, which exists
once per block device.  But given that the block layer also does
partition remapping we additionally need a partition index, which is
used for said remapping in generic_make_request.

Note that all the block drivers generally want request_queue or
sometimes the gendisk, so this removes a layer of indirection all
over the stack.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

No functional change in this patch, just in preparation for
basing the inflight mechanism on the queue in question.
Reviewed-by: NBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

bio_integrity_trim inherent it's interface from bio_trim and accept
offset and size, but this API is error prone because data offset
must always be insync with bio's data offset. That is why we have
integrity update hook in bio_advance()

So only meaningful values are: offset == 0, sectors == bio_sectors(bio)
Let's just remove them completely.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Now all queues allocators come without abounce limit by default,
dm doesn't have to override this anymore.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

A target driver support zoned block devices and exposing it as such may
receive REQ_OP_ZONE_REPORT request for the user to determine the mapped
device zone configuration. To process properly such request, the target
driver may need to remap the zone descriptors provided in the report
reply. The helper function dm_remap_zone_report() does this generically
using only the target start offset and length and the start offset
within the target device.

dm_remap_zone_report() will remap the start sector of all zones
reported. If the report includes sequential zones, the write pointer
position of these zones will also be remapped.
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

A REQ_OP_ZONE_REPORT bio is not a medium access command.  Its number of
sectors indicates the maximum size allowed for the report reply size and
not an amount of sectors accessed from the device.  REQ_OP_ZONE_REPORT
bios should thus not be split depending on the target device maximum I/O
length but passed as-is.  Note that it is the responsability of the
target to remap and format the report reply.
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

The REQ_OP_ZONE_RESET bio has no payload and zero sectors.  Its position
is the only information used to indicate the zone to reset on the
device.  Due to its zero length, this bio is not cloned and sent to the
target through the non-flush case in __split_and_process_bio().  Add an
additional case in that function to call __split_and_process_non_flush()
without checking the clone info size.
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Add the ability to poll on the /dev/mapper/control device.  The select
or poll function waits until any event happens on any dm device since
opening the /dev/mapper/control device.  When select or poll returns the
device as readable, we must close and reopen the device to wait for new
dm events.

Usage:
1. open the /dev/mapper/control device
2. scan the event numbers of all devices we are interested in and process
   them
3. call select, poll or epoll on the handle (it waits until some new event
   happens since opening the device)
4. close the /dev/mapper/control handle
5. go to step 1

The next commit allows to re-arm the polling without closing and
reopening the device.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NAndy Grover <agrover@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

This patch converts bioset_create() to not create a workqueue by
default, so alloctions will never trigger punt_bios_to_rescuer().  It
also introduces a new flag BIOSET_NEED_RESCUER which tells
bioset_create() to preserve the old behavior.

All callers of bioset_create() that are inside block device drivers,
are given the BIOSET_NEED_RESCUER flag.

biosets used by filesystems or other top-level users do not
need rescuing as the bio can never be queued behind other
bios.  This includes fs_bio_set, blkdev_dio_pool,
btrfs_bioset, xfs_ioend_bioset, and one allocated by
target_core_iblock.c.

biosets used by md/raid do not need rescuing as
their usage was recently audited and revised to never
risk deadlock.

It is hoped that most, if not all, of the remaining biosets
can end up being the non-rescued version.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Credit-to: Ming Lei <ming.lei@redhat.com> (minor fixes)
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

"flags" arguments are often seen as good API design as they allow
easy extensibility.
bioset_create_nobvec() is implemented internally as a variation in
flags passed to __bioset_create().

To support future extension, make the internal structure part of the
API.
i.e. add a 'flags' argument to bioset_create() and discard
bioset_create_nobvec().

Note that the bio_split allocations in drivers/md/raid* do not need
the bvec mempool - they should have used bioset_create_nobvec().
Suggested-by: NChristoph Hellwig <hch@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@infradead.org>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Allow device-mapper to route flush operations to the
per-target implementation. In order for the device stacking to work we
need a dax_dev and a pgoff relative to that device. This gives each
layer of the stack the information it needs to look up the operation
pointer for the next level.

This conceptually allows for an array of mixed device drivers with
varying flush implementations.
Reviewed-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

Allow device-mapper to route copy_from_iter operations to the
per-target implementation. In order for the device stacking to work we
need a dax_dev and a pgoff relative to that device. This gives each
layer of the stack the information it needs to look up the operation
pointer for the next level.

This conceptually allows for an array of mixed device drivers with
varying copy_from_iter implementations.
Reviewed-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

Replace bi_error with a new bi_status to allow for a clear conversion.
Note that device mapper overloaded bi_error with a private value, which
we'll have to keep arround at least for now and thus propagate to a
proper blk_status_t value.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

Turn the error paramter into a pointer so that target drivers can change
the value, and make sure only DM_ENDIO_* values are returned from the
methods.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Instead use the special DM_MAPIO_KILL return value to return -EIO just
like we do for the request based path.  Note that dm-log-writes returned
-ENOMEM in a few places, which now becomes -EIO instead.  No consumer
treats -ENOMEM special so this shouldn't be an issue (and it should
use a mempool to start with to make guaranteed progress).
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Commit b685d3d6 ("block: treat REQ_FUA and REQ_PREFLUSH as
synchronous") removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
definitions.  generic_make_request_checks() however strips REQ_FUA and
REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
write cache and thus write effectively becomes asynchronous which can
lead to performance regressions.

Fix the problem by making sure all bios which are synchronous are
properly marked with REQ_SYNC.

Fixes: b685d3d6 ("block: treat REQ_FUA and REQ_PREFLUSH as synchronous")
Cc: stable@vger.kernel.org
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

I/O errors triggered by multipathd incorrectly not enabling the no-flush
flag for DM_DEVICE_SUSPEND or DM_DEVICE_RESUME are hard to debug.  Add
more logging to make it easier to debug this.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Introduce an enumeration type for the queue mode.  This patch does
not change any functionality but makes the DM code easier to read.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Ensure that the assumptions about the caller holding suspend_lock
are checked at runtime if lockdep is enabled.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Now that all the producers and consumers of dax interfaces have been
converted to using dax_operations on a dax_device, remove the block
device direct_access enabling.
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

Arrange for dm to lookup the dax services available from member devices.
Update the dax-capable targets, linear and stripe, to route dax
operations to the underlying device. Changes the target-internal
->direct_access() method to more closely align with the dax_operations
->direct_access() calling convention.

Cc: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

A dm-crypt on dm-integrity device incorrectly advertises an integrity
profile on the DM crypt device.  It can be seen in the files
"/sys/block/dm-*/integrity/*" that both dm-integrity and dm-crypt target
advertise the integrity profile.  That is incorrect, only the
dm-integrity target should advertise the integrity profile.

A general problem in DM is that if we have a DM device that depends on
another device with an integrity profile, the upper device will always
advertise the integrity profile, even when the target driver doesn't
support handling integrity data.

Most targets don't support integrity data, so we provide a whitelist of
targets that support it (linear, delay and striped).  The targets that
support passing integrity data to the lower device are marked with the
flag DM_TARGET_PASSES_INTEGRITY.  The DM core will now advertise
integrity data on a DM device only if all the targets support the
integrity data.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

Allocate a dax_device to represent the capacity of a device-mapper
instance. Provide a ->direct_access() method via the new dax_operations
indirection that mirrors the functionality of the current direct_access
support via block_device_operations.  Once fs/dax.c has been converted
to use dax_operations the old dm_blk_direct_access() will be removed.

A new helper dm_dax_get_live_target() is introduced to separate some of
the dm-specifics from the direct_access implementation.

This enabling is only for the top-level dm representation to upper
layers. Converting target direct_access implementations is deferred to a
separate patch.

Cc: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

Copy & paste from the REQ_OP_WRITE_SAME code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently only dm and md/raid5 bios trigger
trace_block_bio_complete().  Now that we have bio_chain() and
bio_inc_remaining(), it is not possible, in general, for a driver to
know when the bio is really complete.  Only bio_endio() knows that.

So move the trace_block_bio_complete() call to bio_endio().

Now trace_block_bio_complete() pairs with trace_block_bio_queue().
Any bio for which a 'queue' event is traced, will subsequently
generate a 'complete' event.

There are a few cases where completion tracing is not wanted.
1/ If blk_update_request() has already generated a completion
   trace event at the 'request' level, there is no point generating
   one at the bio level too.  In this case the bi_sector and bi_size
   will have changed, so the bio level event would be wrong

2/ If the bio hasn't actually been queued yet, but is being aborted
   early, then a trace event could be confusing.  Some filesystems
   call bio_endio() but do not want tracing.

3/ The bio_integrity code interposes itself by replacing bi_end_io,
   then restoring it and calling bio_endio() again.  This would produce
   two identical trace events if left like that.

To handle these, we introduce a flag BIO_TRACE_COMPLETION and only
produce the trace event when this is set.
We address point 1 above by clearing the flag in blk_update_request().
We address point 2 above by only setting the flag when
generic_make_request() is called.
We address point 3 above by clearing the flag after generating a
completion event.

When bio_split() is used on a bio, particularly in blk_queue_split(),
there is an extra complication.  A new bio is split off the front, and
may be handle directly without going through generic_make_request().
The old bio, which has been advanced, is passed to
generic_make_request(), so it will trigger a trace event a second
time.
Probably the best result when a split happens is to see a single
'queue' event for the whole bio, then multiple 'complete' events - one
for each component.  To achieve this was can:
- copy the BIO_TRACE_COMPLETION flag to the new bio in bio_split()
- avoid generating a 'queue' event if BIO_TRACE_COMPLETION is already set.
This way, the split-off bio won't create a queue event, the original
won't either even if it re-submitted to generic_make_request(),
but both will produce completion events, each for their own range.

So if generic_make_request() is called (which generates a QUEUED
event), then bi_endio() will create a single COMPLETE event for each
range that the bio is split into, unless the driver has explicitly
requested it not to.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Commit 79bd9959 ("blk: improve order of bio handling in generic_make_request()")
changed current->bio_list so that it did not contain *all* of the
queued bios, but only those submitted by the currently running
make_request_fn.

There are two places which walk the list and requeue selected bios,
and others that check if the list is empty.  These are no longer
correct.

So redefine current->bio_list to point to an array of two lists, which
contain all queued bios, and adjust various code to test or walk both
lists.
Signed-off-by: NNeilBrown <neilb@suse.com>
Fixes: 79bd9959 ("blk: improve order of bio handling in generic_make_request()")
Signed-off-by: NJens Axboe <axboe@fb.com>

sched/headers: Prepare to move signal wakeup & sigpending methods from <linux/sched.h> into <linux/sched/signal.h>

Fix up affected files that include this signal functionality via sched.h.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Commit df2cb6da ("block: Avoid deadlocks with bio allocation by
stacking drivers") created a workqueue for every bio set and code
in bio_alloc_bioset() that tries to resolve some low-memory deadlocks
by redirecting bios queued on current->bio_list to the workqueue if the
system is low on memory.  However other deadlocks (see below **) may
happen, without any low memory condition, because generic_make_request
is queuing bios to current->bio_list (rather than submitting them).

** the related dm-snapshot deadlock is detailed here:
https://www.redhat.com/archives/dm-devel/2016-July/msg00065.html

Fix this deadlock by redirecting any bios on current->bio_list to the
bio_set's rescue workqueue on every schedule() call.  Consequently,
when the process blocks on a mutex, the bios queued on
current->bio_list are dispatched to independent workqueus and they can
complete without waiting for the mutex to be available.

The structure blk_plug contains an entry cb_list and this list can contain
arbitrary callback functions that are called when the process blocks.
To implement this fix DM (ab)uses the onstack plug's cb_list interface
to get its flush_current_bio_list() called at schedule() time.

This fixes the snapshot deadlock - if the map method blocks,
flush_current_bio_list() will be called and it redirects bios waiting
on current->bio_list to appropriate workqueues.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1267650
Depends-on: df2cb6da ("block: Avoid deadlocks with bio allocation by stacking drivers")
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

.. at least for unprivileged users.  Before we called into the SCSI
ioctl code to allow excemptions for a few SCSI passthrough ioctls,
but this is pretty unsafe and except for this call dm knows nothing
about SCSI ioctls.

As the SCSI ioctl code is now optional, we really don't want to
drag it in for DM, and the exception is not very useful anyway.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NMike Snitzer <snitzer@redhat.com>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NJohannes Thumshirn <jthumshirn@kernel.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

We will want to have struct backing_dev_info allocated separately from
struct request_queue. As the first step add pointer to backing_dev_info
to request_queue and convert all users touching it. No functional
changes in this patch.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>