bdev_get_queue() returns the request_queue associated with the
specified block_device.  blk_get_backing_dev_info() makes use of
bdev_get_queue() to determine the associated bdi given a block_device.

All the callers of bdev_get_queue() including
blk_get_backing_dev_info() assume that bdev_get_queue() may return
NULL and implement NULL handling; however, bdev_get_queue() requires
the passed in block_device is opened and attached to its gendisk.
Because an active gendisk always has a valid request_queue associated
with it, bdev_get_queue() can never return NULL and neither can
blk_get_backing_dev_info().

Make it clear that neither of the two functions can return NULL and
remove NULL handling from all the callers.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

blkcg->id is a unique id given to each blkcg; however, the
cgroup_subsys_state which each blkcg embeds already has ->serial_nr
which can be used for the same purpose.  Drop blkcg->id and replace
its uses with blkcg->css.serial_nr.  Rename cfq_cgroup->blkcg_id to
->blkcg_serial_nr and @id in check_blkcg_changed() to @serial_nr for
consistency.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Dan writes:

block/bsg.c:327 bsg_map_hdr() error: 'next_rq' dereferencing possible
ERR_PTR().

Fix this by setting next_rq to NULL, for the case where it can be
!= NULL but an error pointer.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

The blk_get_request function may fail in low-memory conditions or during
device removal (even if __GFP_WAIT is set). To distinguish between these
errors, modify the blk_get_request call stack to return the appropriate
ERR_PTR. Verify that all callers check the return status and consider
IS_ERR instead of a simple NULL pointer check.

For consistency, make a similar change to the blk_mq_alloc_request leg
of blk_get_request.  It may fail if the queue is dead, or the caller was
unwilling to wait.
Signed-off-by: NJoe Lawrence <joe.lawrence@stratus.com>
Acked-by: Jiri Kosina <jkosina@suse.cz> [for pktdvd]
Acked-by: Boaz Harrosh <bharrosh@panasas.com> [for osd]
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

The blk-core dead queue checks introduce an error scenario to
blk_get_request that returns NULL if the request queue has been
shutdown. This affects the behavior for __GFP_WAIT callers, who should
verify the return value before dereferencing.
Signed-off-by: NJoe Lawrence <joe.lawrence@stratus.com>
Acked-by: Jiri Kosina <jkosina@suse.cz> [for pktdvd]
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

The lvip[] array has "state->limit" elements so the condition here
should be >= instead of >.

Fixes: 6ceea22b ('partitions: add aix lvm partition support files')
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NPhilippe De Muyter <phdm@macqel.be>
Signed-off-by: NJens Axboe <axboe@fb.com>

Various subsystems can ask the bio subsystem to create a bio slab cache
with some free space before the bio.  This free space can be used for any
purpose.  Device mapper uses this per-bio-data feature to place some
target-specific and device-mapper specific data before the bio, so that
the target-specific data doesn't have to be allocated separately.

This per-bio-data mechanism is used in place of kmalloc, so we need the
allocated slab to have the same memory alignment as memory allocated
with kmalloc.

Change bio_find_or_create_slab() so that it uses ARCH_KMALLOC_MINALIGN
alignment when creating the slab cache.  This is needed so that dm-crypt
can use per-bio-data for encryption - the crypto subsystem assumes this
data will have the same alignment as kmalloc'ed memory.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Acked-by: NJens Axboe <axboe@fb.com>

While a queue is being destroyed, all the blkgs are destroyed and its
->root_blkg pointer is set to NULL.  If someone else starts to drain
while the queue is in this state, the following oops happens.

  NULL pointer dereference at 0000000000000028
  IP: [<ffffffff8144e944>] blk_throtl_drain+0x84/0x230
  PGD e4a1067 PUD b773067 PMD 0
  Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
  Modules linked in: cfq_iosched(-) [last unloaded: cfq_iosched]
  CPU: 1 PID: 537 Comm: bash Not tainted 3.16.0-rc3-work+ #2
  Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
  task: ffff88000e222250 ti: ffff88000efd4000 task.ti: ffff88000efd4000
  RIP: 0010:[<ffffffff8144e944>]  [<ffffffff8144e944>] blk_throtl_drain+0x84/0x230
  RSP: 0018:ffff88000efd7bf0  EFLAGS: 00010046
  RAX: 0000000000000000 RBX: ffff880015091450 RCX: 0000000000000001
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
  RBP: ffff88000efd7c10 R08: 0000000000000000 R09: 0000000000000001
  R10: ffff88000e222250 R11: 0000000000000000 R12: ffff880015091450
  R13: ffff880015092e00 R14: ffff880015091d70 R15: ffff88001508fc28
  FS:  00007f1332650740(0000) GS:ffff88001fa80000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
  CR2: 0000000000000028 CR3: 0000000009446000 CR4: 00000000000006e0
  Stack:
   ffffffff8144e8f6 ffff880015091450 0000000000000000 ffff880015091d80
   ffff88000efd7c28 ffffffff8144ae2f ffff880015091450 ffff88000efd7c58
   ffffffff81427641 ffff880015091450 ffffffff82401f00 ffff880015091450
  Call Trace:
   [<ffffffff8144ae2f>] blkcg_drain_queue+0x1f/0x60
   [<ffffffff81427641>] __blk_drain_queue+0x71/0x180
   [<ffffffff81429b3e>] blk_queue_bypass_start+0x6e/0xb0
   [<ffffffff814498b8>] blkcg_deactivate_policy+0x38/0x120
   [<ffffffff8144ec44>] blk_throtl_exit+0x34/0x50
   [<ffffffff8144aea5>] blkcg_exit_queue+0x35/0x40
   [<ffffffff8142d476>] blk_release_queue+0x26/0xd0
   [<ffffffff81454968>] kobject_cleanup+0x38/0x70
   [<ffffffff81454848>] kobject_put+0x28/0x60
   [<ffffffff81427505>] blk_put_queue+0x15/0x20
   [<ffffffff817d07bb>] scsi_device_dev_release_usercontext+0x16b/0x1c0
   [<ffffffff810bc339>] execute_in_process_context+0x89/0xa0
   [<ffffffff817d064c>] scsi_device_dev_release+0x1c/0x20
   [<ffffffff817930e2>] device_release+0x32/0xa0
   [<ffffffff81454968>] kobject_cleanup+0x38/0x70
   [<ffffffff81454848>] kobject_put+0x28/0x60
   [<ffffffff817934d7>] put_device+0x17/0x20
   [<ffffffff817d11b9>] __scsi_remove_device+0xa9/0xe0
   [<ffffffff817d121b>] scsi_remove_device+0x2b/0x40
   [<ffffffff817d1257>] sdev_store_delete+0x27/0x30
   [<ffffffff81792ca8>] dev_attr_store+0x18/0x30
   [<ffffffff8126f75e>] sysfs_kf_write+0x3e/0x50
   [<ffffffff8126ea87>] kernfs_fop_write+0xe7/0x170
   [<ffffffff811f5e9f>] vfs_write+0xaf/0x1d0
   [<ffffffff811f69bd>] SyS_write+0x4d/0xc0
   [<ffffffff81d24692>] system_call_fastpath+0x16/0x1b

776687bc ("block, blk-mq: draining can't be skipped even if
bypass_depth was non-zero") made it easier to trigger this bug by
making blk_queue_bypass_start() drain even when it loses the first
bypass test to blk_cleanup_queue(); however, the bug has always been
there even before the commit as blk_queue_bypass_start() could race
against queue destruction, win the initial bypass test but perform the
actual draining after blk_cleanup_queue() already destroyed all blkgs.

Fix it by skippping calling into policy draining if all the blkgs are
already gone.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NShirish Pargaonkar <spargaonkar@suse.com>
Reported-by: NSasha Levin <sasha.levin@oracle.com>
Reported-by: NJet Chen <jet.chen@intel.com>
Cc: stable@vger.kernel.org
Tested-by: NShirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently, cftypes added by cgroup_add_cftypes() are used for both the
unified default hierarchy and legacy ones and subsystems can mark each
file with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE if it has to
appear only on one of them.  This is quite hairy and error-prone.
Also, we may end up exposing interface files to the default hierarchy
without thinking it through.

cgroup_subsys will grow two separate cftype addition functions and
apply each only on the hierarchies of the matching type.  This will
allow organizing cftypes in a lot clearer way and encourage subsystems
to scrutinize the interface which is being exposed in the new default
hierarchy.

In preparation, this patch adds cgroup_add_legacy_cftypes() which
currently is a simple wrapper around cgroup_add_cftypes() and replaces
all cgroup_add_cftypes() usages with it.

While at it, this patch drops a completely spurious return from
__hugetlb_cgroup_file_init().

This patch doesn't introduce any functional differences.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Acked-by: NLi Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

Currently, cgroup_subsys->base_cftypes is used for both the unified
default hierarchy and legacy ones and subsystems can mark each file
with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE if it has to appear
only on one of them.  This is quite hairy and error-prone.  Also, we
may end up exposing interface files to the default hierarchy without
thinking it through.

cgroup_subsys will grow two separate cftype arrays and apply each only
on the hierarchies of the matching type.  This will allow organizing
cftypes in a lot clearer way and encourage subsystems to scrutinize
the interface which is being exposed in the new default hierarchy.

In preparation, this patch renames cgroup_subsys->base_cftypes to
cgroup_subsys->legacy_cftypes.  This patch is pure rename.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Acked-by: NLi Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

This reverts commit 254c4407.

It causes crashes with cryptsetup, even after a few iterations and
updates. Drop it for now.

This patch provides the compat BLKZEROOUT ioctl. The argument is a pointer
to two uint64_t values, so there is no need to translate it.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org	# 3.7+
Acked-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

While a queue is being destroyed, all the blkgs are destroyed and its
->root_blkg pointer is set to NULL.  If someone else starts to drain
while the queue is in this state, the following oops happens.

  NULL pointer dereference at 0000000000000028
  IP: [<ffffffff8144e944>] blk_throtl_drain+0x84/0x230
  PGD e4a1067 PUD b773067 PMD 0
  Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
  Modules linked in: cfq_iosched(-) [last unloaded: cfq_iosched]
  CPU: 1 PID: 537 Comm: bash Not tainted 3.16.0-rc3-work+ #2
  Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
  task: ffff88000e222250 ti: ffff88000efd4000 task.ti: ffff88000efd4000
  RIP: 0010:[<ffffffff8144e944>]  [<ffffffff8144e944>] blk_throtl_drain+0x84/0x230
  RSP: 0018:ffff88000efd7bf0  EFLAGS: 00010046
  RAX: 0000000000000000 RBX: ffff880015091450 RCX: 0000000000000001
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
  RBP: ffff88000efd7c10 R08: 0000000000000000 R09: 0000000000000001
  R10: ffff88000e222250 R11: 0000000000000000 R12: ffff880015091450
  R13: ffff880015092e00 R14: ffff880015091d70 R15: ffff88001508fc28
  FS:  00007f1332650740(0000) GS:ffff88001fa80000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
  CR2: 0000000000000028 CR3: 0000000009446000 CR4: 00000000000006e0
  Stack:
   ffffffff8144e8f6 ffff880015091450 0000000000000000 ffff880015091d80
   ffff88000efd7c28 ffffffff8144ae2f ffff880015091450 ffff88000efd7c58
   ffffffff81427641 ffff880015091450 ffffffff82401f00 ffff880015091450
  Call Trace:
   [<ffffffff8144ae2f>] blkcg_drain_queue+0x1f/0x60
   [<ffffffff81427641>] __blk_drain_queue+0x71/0x180
   [<ffffffff81429b3e>] blk_queue_bypass_start+0x6e/0xb0
   [<ffffffff814498b8>] blkcg_deactivate_policy+0x38/0x120
   [<ffffffff8144ec44>] blk_throtl_exit+0x34/0x50
   [<ffffffff8144aea5>] blkcg_exit_queue+0x35/0x40
   [<ffffffff8142d476>] blk_release_queue+0x26/0xd0
   [<ffffffff81454968>] kobject_cleanup+0x38/0x70
   [<ffffffff81454848>] kobject_put+0x28/0x60
   [<ffffffff81427505>] blk_put_queue+0x15/0x20
   [<ffffffff817d07bb>] scsi_device_dev_release_usercontext+0x16b/0x1c0
   [<ffffffff810bc339>] execute_in_process_context+0x89/0xa0
   [<ffffffff817d064c>] scsi_device_dev_release+0x1c/0x20
   [<ffffffff817930e2>] device_release+0x32/0xa0
   [<ffffffff81454968>] kobject_cleanup+0x38/0x70
   [<ffffffff81454848>] kobject_put+0x28/0x60
   [<ffffffff817934d7>] put_device+0x17/0x20
   [<ffffffff817d11b9>] __scsi_remove_device+0xa9/0xe0
   [<ffffffff817d121b>] scsi_remove_device+0x2b/0x40
   [<ffffffff817d1257>] sdev_store_delete+0x27/0x30
   [<ffffffff81792ca8>] dev_attr_store+0x18/0x30
   [<ffffffff8126f75e>] sysfs_kf_write+0x3e/0x50
   [<ffffffff8126ea87>] kernfs_fop_write+0xe7/0x170
   [<ffffffff811f5e9f>] vfs_write+0xaf/0x1d0
   [<ffffffff811f69bd>] SyS_write+0x4d/0xc0
   [<ffffffff81d24692>] system_call_fastpath+0x16/0x1b

776687bc ("block, blk-mq: draining can't be skipped even if
bypass_depth was non-zero") made it easier to trigger this bug by
making blk_queue_bypass_start() drain even when it loses the first
bypass test to blk_cleanup_queue(); however, the bug has always been
there even before the commit as blk_queue_bypass_start() could race
against queue destruction, win the initial bypass test but perform the
actual draining after blk_cleanup_queue() already destroyed all blkgs.

Fix it by skippping calling into policy draining if all the blkgs are
already gone.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NShirish Pargaonkar <spargaonkar@suse.com>
Reported-by: NSasha Levin <sasha.levin@oracle.com>
Reported-by: NJet Chen <jet.chen@intel.com>
Cc: stable@vger.kernel.org
Tested-by: NShirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

sane_behavior has been used as a development vehicle for the default
unified hierarchy.  Now that the default hierarchy is in place, the
flag became redundant and confusing as its usage is allowed on all
hierarchies.  There are gonna be either the default hierarchy or
legacy ones.  Let's make that clear by removing sane_behavior support
on non-default hierarchies.

This patch replaces cgroup_sane_behavior() with cgroup_on_dfl().  The
comment on top of CGRP_ROOT_SANE_BEHAVIOR is moved to on top of
cgroup_on_dfl() with sane_behavior specific part dropped.

On the default and legacy hierarchies w/o sane_behavior, this
shouldn't cause any behavior differences.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Acked-by: NLi Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>

Currently, the blkio subsystem attributes all of writeback IOs to the
root.  One of the issues is that there's no way to tell who originated
a writeback IO from block layer.  Those IOs are usually issued
asynchronously from a task which didn't have anything to do with
actually generating the dirty pages.  The memory subsystem, when
enabled, already keeps track of the ownership of each dirty page and
it's desirable for blkio to piggyback instead of adding its own
per-page tag.

cgroup now has a mechanism to express such dependency -
cgroup_subsys->depends_on.  This patch declares that blkcg depends on
memcg so that memcg is enabled automatically on the default hierarchy
when available.  Future changes will make blkcg map the memcg tag to
find out the cgroup to blame for writeback IOs.

As this means that a memcg may be made invisible, this patch also
implements css_reset() for memcg which resets its basic
configurations.  This implementation will probably need to be expanded
to cover other states which are used in the default hierarchy.

v2: blkcg's dependency on memcg is wrapped with CONFIG_MEMCG to avoid
    build failure.  Reported by kbuild test robot.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>

There is no inherent reason why the last put of a tag structure must be
the one for the Scsi_Host, as device model objects can be held for
arbitrary periods.  Merge blk_free_tags and __blk_free_tags into a single
funtion that just release a references and get rid of the BUG() when the
host reference wasn't the last.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Cc: stable@kernel.org
Signed-off-by: NJens Axboe <axboe@fb.com>

The original behaviour is to refuse to add a new page if the maximum
number of segments has been reached, regardless of the fact the page we
are going to add can be merged into the last segment or not.

Unfortunately, when the system runs under heavy memory fragmentation
conditions, a driver may try to add multiple pages to the last segment.
The original code won't accept them and EBUSY will be reported to
userspace.

This patch modifies the function so it refuses to add a page only in case
the latter starts a new segment and the maximum number of segments has
already been reached.

The bug can be easily reproduced with the st driver:

1) set CONFIG_SCSI_MPT2SAS_MAX_SGE or CONFIG_SCSI_MPT3SAS_MAX_SGE  to 16
2) modprobe st buffer_kbs=1024
3) #dd if=/dev/zero of=/dev/st0 bs=1M count=10
   dd: error writing `/dev/st0': Device or resource busy

[ming.lei@canonical.com: update bi_iter.bi_size before recounting segments]
Signed-off-by: NMaurizio Lombardi <mlombard@redhat.com>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NDongsu Park <dongsu.park@profitbricks.com>
Tested-by: NJet Chen <jet.chen@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

After the SG_IO ioctl was copied into the block layer and
later into the bsg driver, subtle differences emerged.

One difference is the way injected commands are queued through
the block layer (i.e. this is not SCSI device queueing nor SATA
NCQ). Summarizing:
  - SG_IO on block layer device: blk_exec*(at_head=false)
  - sg device SG_IO: at_head=true
  - bsg device SG_IO: at_head=true

Some time ago Boaz Harrosh introduced a sg v4 flag called
BSG_FLAG_Q_AT_TAIL to override the bsg driver default. A
recent patch titled: "sg: add SG_FLAG_Q_AT_TAIL flag"
allowed the sg driver default to be overridden. This patch
allows a SG_IO ioctl sent to a block layer device to have
its default overridden.

ChangeLog:
    - introduce SG_FLAG_Q_AT_HEAD flag in sg.h to cause
      commands that are injected via a block layer
      device SG_IO ioctl to set at_head=true
    - make comments clearer about queueing in sg.h since the
      header is used both by the sg device and block layer
      device implementations of the SG_IO ioctl.
    - introduce BSG_FLAG_Q_AT_HEAD in bsg.h for compatibility
      (it does nothing) and update comments.
Signed-off-by: NDouglas Gilbert <dgilbert@interlog.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: NJens Axboe <axboe@fb.com>

SG_GET_RESERVED_SIZE and SG_SET_RESERVED_SIZE ioctls access a reserved
buffer in bytes as int type.  The value needs to be capped at the request
queue's max_sectors.  But integer overflow is not correctly handled in
the calculation when converting max_sectors from sectors to bytes.
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: linux-scsi@vger.kernel.org
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

BLKSECTGET ioctl loads the request queue's max_sectors as unsigned
short value to the argument pointer.  So if the max_sector is greater
than USHRT_MAX, the upper 16 bits of that is just discarded.

In such case, USHRT_MAX is more preferable than the lower 16 bits of
max_sectors.
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: linux-scsi@vger.kernel.org
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

Adding function documentation and fixing kerneldoc warnings
('field: description' uniformization).

Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NJens Axboe <axboe@fb.com>

checkpatch fixing:
WARNING: Missing a blank line after declarations
WARNING: space prohibited between function name and open parenthesis '('
ERROR: spaces required around that '<' (ctx:VxV)

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NJens Axboe <axboe@fb.com>

Also add no prefix pr_fmt to avoid any future default format update

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NJens Axboe <axboe@fb.com>

kcalloc manages count*sizeof overflow.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NJens Axboe <axboe@fb.com>

Commit 08778795 ("block: Fix nr_vecs for inline integrity vectors") from
Martin introduces the function bip_integrity_vecs(get the useful vectors)
to fix the issue about nr_vecs for inline integrity vectors that reported
by David Milburn.

But it seems that bip_integrity_vecs() will return the wrong number if the
bio is not based on any bio_set for some reason(bio->bi_pool == NULL),
because in that case, the bip_inline_vecs[0] is malloced directly.  So
here we add the bip_max_vcnt to record the count of vector slots, and
cleanup the function bip_integrity_vecs().
Signed-off-by: NGu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently, blk-mq uses a percpu_counter to keep track of how many
usages are in flight.  The percpu_counter is drained while freezing to
ensure that no usage is left in-flight after freezing is complete.
blk_mq_queue_enter/exit() and blk_mq_[un]freeze_queue() implement this
per-cpu gating mechanism.

This type of code has relatively high chance of subtle bugs which are
extremely difficult to trigger and it's way too hairy to be open coded
in blk-mq.  percpu_ref can serve the same purpose after the recent
changes.  This patch replaces the open-coded per-cpu usage counting
and draining mechanism with percpu_ref.

blk_mq_queue_enter() performs tryget_live on the ref and exit()
performs put.  blk_mq_freeze_queue() kills the ref and waits until the
reference count reaches zero.  blk_mq_unfreeze_queue() revives the ref
and wakes up the waiters.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Keeping __blk_mq_drain_queue() as a separate function doesn't buy us
anything and it's gonna be further simplified.  Let's flatten it into
its caller.

This patch doesn't make any functional change.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

blk_mq freezing is entangled with generic bypassing which bypasses
blkcg and io scheduler and lets IO requests fall through the block
layer to the drivers in FIFO order.  This allows forward progress on
IOs with the advanced features disabled so that those features can be
configured or altered without worrying about stalling IO which may
lead to deadlock through memory allocation.

However, generic bypassing doesn't quite fit blk-mq.  blk-mq currently
doesn't make use of blkcg or ioscheds and it maps bypssing to
freezing, which blocks request processing and drains all the in-flight
ones.  This causes problems as bypassing assumes that request
processing is online.  blk-mq works around this by conditionally
allowing request processing for the problem case - during queue
initialization.

Another weirdity is that except for during queue cleanup, bypassing
started on the generic side prevents blk-mq from processing new
requests but doesn't drain the in-flight ones.  This shouldn't break
anything but again highlights that something isn't quite right here.

The root cause is conflating blk-mq freezing and generic bypassing
which are two different mechanisms.  The only intersecting purpose
that they serve is during queue cleanup.  Let's properly separate
blk-mq freezing from generic bypassing and simply use it where
necessary.

* request_queue->mq_freeze_depth is added and
  blk_mq_[un]freeze_queue() now operate on this counter instead of
  ->bypass_depth.  The replacement for QUEUE_FLAG_BYPASS isn't added
  but the counter is tested directly.  This will be further updated by
  later changes.

* blk_mq_drain_queue() is dropped and "__" prefix is dropped from
  blk_mq_freeze_queue().  Queue cleanup path now calls
  blk_mq_freeze_queue() directly.

* blk_queue_enter()'s fast path condition is simplified to simply
  check @q->mq_freeze_depth.  Previously, the condition was

	!blk_queue_dying(q) &&
	    (!blk_queue_bypass(q) || !blk_queue_init_done(q))

  mq_freeze_depth is incremented right after dying is set and
  blk_queue_init_done() exception isn't necessary as blk-mq doesn't
  start frozen, which only leaves the blk_queue_bypass() test which
  can be replaced by @q->mq_freeze_depth test.

This change simplifies the code and reduces confusion in the area.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently, both blk_queue_bypass_start() and blk_mq_freeze_queue()
skip queue draining if bypass_depth was already above zero.  The
assumption is that the one which bumped the bypass_depth should have
performed draining already; however, there's nothing which prevents a
new instance of bypassing/freezing from starting before the previous
one finishes draining.  The current code may allow the later
bypassing/freezing instances to complete while there still are
in-flight requests which haven't finished draining.

Fix it by draining regardless of bypass_depth.  We still skip draining
from blk_queue_bypass_start() while the queue is initializing to avoid
introducing excessive delays during boot.  INIT_DONE setting is moved
above the initial blk_queue_bypass_end() so that bypassing attempts
can't slip inbetween.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

blk-mq uses a percpu_counter to keep track of how many usages are in
flight.  The percpu_counter is drained while freezing to ensure that
no usage is left in-flight after freezing is complete.

blk_mq_queue_enter/exit() and blk_mq_[un]freeze_queue() implement this
per-cpu gating mechanism; unfortunately, it contains a subtle bug -
smp_wmb() in blk_mq_queue_enter() doesn't prevent prevent the cpu from
fetching @q->bypass_depth before incrementing @q->mq_usage_counter and
if freezing happens inbetween the caller can slip through and freezing
can be complete while there are active users.

Use smp_mb() instead so that bypass_depth and mq_usage_counter
modifications and tests are properly interlocked.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently it calls __blk_mq_run_hw_queue(), which depends on the
CPU placement being correct. This means it's not possible to call
blk_mq_start_hw_queues(q) from a context that is correct for all
queues, leading to triggering the

WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask));

in __blk_mq_run_hw_queue().
Reported-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Another restriction inherited for NVMe - those devices don't support
SG lists that have "gaps" in them. Gaps refers to cases where the
previous SG entry doesn't end on a page boundary. For NVMe, all SG
entries must start at offset 0 (except the first) and end on a page
boundary (except the last).
Signed-off-by: NJens Axboe <axboe@fb.com>

This reverts commit b5097e95.

The original commit is buggy, we do use the registration functions
at runtime, for instance when loading IO schedulers through sysfs.
Reported-by: NDamien Wyart <damien.wyart@gmail.com>

This reverts commit a2d445d4.

The original commit is buggy, we do use the registration functions
at runtime for modular builds.

Hello,

So, this patch should do.  Joe, Vivek, can one of you guys please
verify that the oops goes away with this patch?

Jens, the original thread can be read at

  http://thread.gmane.org/gmane.linux.kernel/1720729

The fix converts blkg->refcnt from int to atomic_t.  It does some
overhead but it should be minute compared to everything else which is
going on and the involved cacheline bouncing, so I think it's highly
unlikely to cause any noticeable difference.  Also, the refcnt in
question should be converted to a perpcu_ref for blk-mq anyway, so the
atomic_t is likely to go away pretty soon anyway.

Thanks.

------- 8< -------
__blkg_release_rcu() may be invoked after the associated request_queue
is released with a RCU grace period inbetween.  As such, the function
and callbacks invoked from it must not dereference the associated
request_queue.  This is clearly indicated in the comment above the
function.

Unfortunately, while trying to fix a different issue, 2a4fd070
("blkcg: move bulk of blkcg_gq release operations to the RCU
callback") ignored this and added [un]locking of @blkg->q->queue_lock
to __blkg_release_rcu().  This of course can cause oops as the
request_queue may be long gone by the time this code gets executed.

  general protection fault: 0000 [#1] SMP
  CPU: 21 PID: 30 Comm: rcuos/21 Not tainted 3.15.0 #1
  Hardware name: Stratus ftServer 6400/G7LAZ, BIOS BIOS Version 6.3:57 12/25/2013
  task: ffff880854021de0 ti: ffff88085403c000 task.ti: ffff88085403c000
  RIP: 0010:[<ffffffff8162e9e5>]  [<ffffffff8162e9e5>] _raw_spin_lock_irq+0x15/0x60
  RSP: 0018:ffff88085403fdf0  EFLAGS: 00010086
  RAX: 0000000000020000 RBX: 0000000000000010 RCX: 0000000000000000
  RDX: 000060ef80008248 RSI: 0000000000000286 RDI: 6b6b6b6b6b6b6b6b
  RBP: ffff88085403fdf0 R08: 0000000000000286 R09: 0000000000009f39
  R10: 0000000000020001 R11: 0000000000020001 R12: ffff88103c17a130
  R13: ffff88103c17a080 R14: 0000000000000000 R15: 0000000000000000
  FS:  0000000000000000(0000) GS:ffff88107fca0000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00000000006e5ab8 CR3: 000000000193d000 CR4: 00000000000407e0
  Stack:
   ffff88085403fe18 ffffffff812cbfc2 ffff88103c17a130 0000000000000000
   ffff88103c17a130 ffff88085403fec0 ffffffff810d1d28 ffff880854021de0
   ffff880854021de0 ffff88107fcaec58 ffff88085403fe80 ffff88107fcaec30
  Call Trace:
   [<ffffffff812cbfc2>] __blkg_release_rcu+0x72/0x150
   [<ffffffff810d1d28>] rcu_nocb_kthread+0x1e8/0x300
   [<ffffffff81091d81>] kthread+0xe1/0x100
   [<ffffffff8163813c>] ret_from_fork+0x7c/0xb0
  Code: ff 47 04 48 8b 7d 08 be 00 02 00 00 e8 55 48 a4 ff 5d c3 0f 1f 00 66 66 66 66 90 55 48 89 e5
  +fa 66 66 90 66 66 90 b8 00 00 02 00 <f0> 0f c1 07 89 c2 c1 ea 10 66 39 c2 75 02 5d c3 83 e2 fe 0f
  +b7
  RIP  [<ffffffff8162e9e5>] _raw_spin_lock_irq+0x15/0x60
   RSP <ffff88085403fdf0>

The request_queue locking was added because blkcg_gq->refcnt is an int
protected with the queue lock and __blkg_release_rcu() needs to put
the parent.  Let's fix it by making blkcg_gq->refcnt an atomic_t and
dropping queue locking in the function.

Given the general heavy weight of the current request_queue and blkcg
operations, this is unlikely to cause any noticeable overhead.
Moreover, blkcg_gq->refcnt is likely to be converted to percpu_ref in
the near future, so whatever (most likely negligible) overhead it may
add is temporary.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NJoe Lawrence <joe.lawrence@stratus.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Link: http://lkml.kernel.org/g/alpine.DEB.2.02.1406081816540.17948@jlaw-desktop.mno.stratus.com
Cc: stable@vger.kernel.org
Signed-off-by: NJens Axboe <axboe@fb.com>

This update fixes few issues in bt_get() function:

- list_empty(&wait.task_list) check is not protected;

- was_empty check is always true which results in *every* thread
  entering the loop resets bt_wait_state::wait_cnt counter rather
  than every bt->wake_cnt'th thread;

- 'bt_wait_state::wait_cnt' counter update is redundant, since
  it also gets reset in bt_clear_tag() function;

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAlexander Gordeev <agordeev@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This piece of code in bt_clear_tag() function is racy:

	bs = bt_wake_ptr(bt);
	if (bs && atomic_dec_and_test(&bs->wait_cnt)) {
		atomic_set(&bs->wait_cnt, bt->wake_cnt);
 		wake_up(&bs->wait);
	}

Since nothing prevents bt_wake_ptr() from returning the very
same 'bs' address on multiple CPUs, the following scenario is
possible:

    CPU1                                CPU2
    ----                                ----

0.  bs = bt_wake_ptr(bt);               bs = bt_wake_ptr(bt);
1.  atomic_dec_and_test(&bs->wait_cnt)
2.                                      atomic_dec_and_test(&bs->wait_cnt)
3.  atomic_set(&bs->wait_cnt, bt->wake_cnt);

If the decrement in [1] yields zero then for some amount of time
the decrement in [2] results in a negative/overflow value, which
is not expected. The follow-up assignment in [3] overwrites the
invalid value with the batch value (and likely prevents the issue
from being severe) which is still incorrect and should be a lesser.

Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAlexander Gordeev <agordeev@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Fix racy updates of shared blk_mq_bitmap_tags::wake_index
and blk_mq_hw_ctx::wake_index fields.

Cc: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: NAlexander Gordeev <agordeev@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

If we need to drain a queue we need to run all queues, even if they
are marked stopped to make sure the driver has a chance to error out
on all queued requests.

This fixes surprise removal with scsi-mq.
Reported-by: NBart Van Assche <bvanassche@acm.org>
Tested-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@fb.com>