1. Getting next index before continue branch.
2. Checking free bits when setting the target bits. Otherwise,
it may reuse the busying bits.
Signed-off-by: Nwuchi <wuchi.zero@gmail.com>
Reviewed-by: NMartin Wilck <mwilck@suse.com>
Link: https://lore.kernel.org/r/20220605145835.26916-1-wuchi.zero@gmail.com
Fixes: 9672b0d4 ("sbitmap: add __sbitmap_queue_get_batch()")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

sbitmap has been used in scsi for replacing atomic operations on
sdev->device_busy, so IOPS on some fast scsi storage can be improved.

However, sdev->device_busy can be changed in fast path, so we have to
allocate the sb->map statically. sdev->device_busy has been capped to 1024,
but some drivers may configure the default depth as < 8, then
cause each sbitmap word to hold only one bit. Finally 1024 * 128(
sizeof(sbitmap_word)) bytes is needed for sb->map, given it is order 5
allocation, sometimes it may fail.

Avoid the issue by using kvzalloc_node() for allocating sb->map.

Cc: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220316012708.354668-1-ming.lei@redhat.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Since __sbitmap_queue_get_shallow() was introduced in commit c05e6673
("sbitmap: add sbitmap_get_shallow() operation"), it has not been used.

Delete __sbitmap_queue_get_shallow() and rename public
__sbitmap_queue_get_shallow() -> sbitmap_queue_get_shallow() as it is odd
to have public __foo but no foo at all.
Signed-off-by: NJohn Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1644322024-105340-1-git-send-email-john.garry@huawei.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Only the last sbitmap_word can have different depth, and all the others
must have same depth of 1U << sb->shift, so not necessary to store it in
sbitmap_word, and it can be retrieved easily and efficiently by adding
one internal helper of __map_depth(sb, index).

Remove 'depth' field from sbitmap_word, then the annotation of
____cacheline_aligned_in_smp for 'word' isn't needed any more.

Not see performance effect when running high parallel IOPS test on
null_blk.

This way saves us one cacheline(usually 64 words) per each sbitmap_word.

Cc: Martin Wilck <martin.wilck@suse.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NMartin Wilck <mwilck@suse.com>
Reviewed-by: NJohn Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20220110072945.347535-1-ming.lei@redhat.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Commit 180dccb0 ("blk-mq: fix tag_get wait task can't be
awakened") will recalculate wake_batch when incrementing or decrementing
active_queues to avoid wake_batch > hctx_max_depth. At the same time, in
order to not affect performance as much as possible, the minimum wakeup
batch is set to 4. But when the QD is small (such as QD=1), if inc or dec
active_queues increases wakeup batch, that can lead to a hang:

Fix this problem with the following strategies:
QD          :  >= 32 | < 32
---------------------------------
wakeup batch:  8~4   | 3~1

Fixes: 180dccb0 ("blk-mq: fix tag_get wait task can't be awakened")
Link: https://lore.kernel.org/linux-block/78cafe94-a787-e006-8851-69906f0c2128@huawei.com/T/#tReported-by: NAlex Xu (Hello71) <alex_y_xu@yahoo.ca>
Signed-off-by: NLaibin Qiu <qiulaibin@huawei.com>
Tested-by: NAlex Xu (Hello71) <alex_y_xu@yahoo.ca>
Link: https://lore.kernel.org/r/20220127100047.1763746-1-qiulaibin@huawei.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

In case of shared tags, there might be more than one hctx which
allocates from the same tags, and each hctx is limited to allocate at
most:
        hctx_max_depth = max((bt->sb.depth + users - 1) / users, 4U);

tag idle detection is lazy, and may be delayed for 30sec, so there
could be just one real active hctx(queue) but all others are actually
idle and still accounted as active because of the lazy idle detection.
Then if wake_batch is > hctx_max_depth, driver tag allocation may wait
forever on this real active hctx.

Fix this by recalculating wake_batch when inc or dec active_queues.

Fixes: 0d2602ca ("blk-mq: improve support for shared tags maps")
Suggested-by: NMing Lei <ming.lei@redhat.com>
Suggested-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NLaibin Qiu <qiulaibin@huawei.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220113025536.1479653-1-qiulaibin@huawei.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

KCSAN complaints about the sbitmap hint update:

==================================================================
BUG: KCSAN: data-race in sbitmap_queue_clear / sbitmap_queue_clear

write to 0xffffe8ffffd145b8 of 4 bytes by interrupt on cpu 1:
 sbitmap_queue_clear+0xca/0xf0 lib/sbitmap.c:606
 blk_mq_put_tag+0x82/0x90
 __blk_mq_free_request+0x114/0x180 block/blk-mq.c:507
 blk_mq_free_request+0x2c8/0x340 block/blk-mq.c:541
 __blk_mq_end_request+0x214/0x230 block/blk-mq.c:565
 blk_mq_end_request+0x37/0x50 block/blk-mq.c:574
 lo_complete_rq+0xca/0x170 drivers/block/loop.c:541
 blk_complete_reqs block/blk-mq.c:584 [inline]
 blk_done_softirq+0x69/0x90 block/blk-mq.c:589
 __do_softirq+0x12c/0x26e kernel/softirq.c:558
 run_ksoftirqd+0x13/0x20 kernel/softirq.c:920
 smpboot_thread_fn+0x22f/0x330 kernel/smpboot.c:164
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30

write to 0xffffe8ffffd145b8 of 4 bytes by interrupt on cpu 0:
 sbitmap_queue_clear+0xca/0xf0 lib/sbitmap.c:606
 blk_mq_put_tag+0x82/0x90
 __blk_mq_free_request+0x114/0x180 block/blk-mq.c:507
 blk_mq_free_request+0x2c8/0x340 block/blk-mq.c:541
 __blk_mq_end_request+0x214/0x230 block/blk-mq.c:565
 blk_mq_end_request+0x37/0x50 block/blk-mq.c:574
 lo_complete_rq+0xca/0x170 drivers/block/loop.c:541
 blk_complete_reqs block/blk-mq.c:584 [inline]
 blk_done_softirq+0x69/0x90 block/blk-mq.c:589
 __do_softirq+0x12c/0x26e kernel/softirq.c:558
 run_ksoftirqd+0x13/0x20 kernel/softirq.c:920
 smpboot_thread_fn+0x22f/0x330 kernel/smpboot.c:164
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30

value changed: 0x00000035 -> 0x00000044

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10 Comm: ksoftirqd/0 Not tainted 5.15.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

which is a data race, but not an important one. This is just updating the
percpu alloc hint, and the reader of that hint doesn't ever require it to
be valid.

Just annotate it with data_race() to silence this one.

Reported-by: syzbot+4f8bfd804b4a1f95b8f6@syzkaller.appspotmail.com
Acked-by: NMarco Elver <elver@google.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

sbitmap currently only supports clearing tags one-by-one, add a helper
that allows the caller to pass in an array of tags to clear.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The block layer tag allocation batching still calls into sbitmap to get
each tag, but we can improve on that. Add __sbitmap_queue_get_batch(),
which returns a mask of tags all at once, along with an offset for
those tags.

An example return would be 0xff, where bits 0..7 are set, with
tag_offset == 128. The valid tags in this case would be 128..135.

A batch is specific to an individual sbitmap_map, hence it cannot be
larger than that. The requested number of tags is automatically reduced
to the max that can be satisfied with a single map.

On failure, 0 is returned. Caller should fall back to single tag
allocation at that point/
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Fix some spelling mistakes in comments:
permanentely ==> permanently
wont ==> won't
remaning ==> remaining
succed ==> succeed
shouldnt ==> shouldn't
alpha-numeric ==> alphanumeric
storeing ==> storing
funtion ==> function
documenation ==> documentation
Determin ==> Determine
intepreted ==> interpreted
ammount ==> amount
obious ==> obvious
interupts ==> interrupts
occured ==> occurred
asssociated ==> associated
taking into acount ==> taking into account
squence ==> sequence
stil ==> still
contiguos ==> contiguous
matchs ==> matches

Link: https://lkml.kernel.org/r/20210607072555.12416-1-thunder.leizhen@huawei.comSigned-off-by: NZhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: NJacob Keller <jacob.e.keller@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Move code for calculating default shift into a public helper which can be
used by SCSI.

Link: https://lore.kernel.org/r/20210122023317.687987-7-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Tested-by: NSumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

SCSI's .device_busy will be converted to sbitmap and sbitmap_weight is
needed. Export the helper.

The only existing user of sbitmap_weight() uses it to find out how many
bits are set and not cleared. Align sbitmap_weight() meaning with this
usage model.

Link: https://lore.kernel.org/r/20210122023317.687987-6-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Tested-by: NSumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

Allocation hint should have belonged to sbitmap. Also, when sbitmap's depth
is high and there is no need to use mulitple wakeup queues, user can
benefit from percpu allocation hint too.

Move allocation hint into sbitmap, then SCSI device queue can benefit from
allocation hint when converting to plain sbitmap.

Convert vhost/scsi.c to use sbitmap allocation with percpu alloc hint. This
is more efficient than the previous approach.

Link: https://lore.kernel.org/r/20210122023317.687987-5-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: virtualization@lists.linux-foundation.org
Tested-by: NSumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

Add helpers for updating allocation hint so that we can avoid duplicate
code.

Prepare for moving allocation hint into sbitmap.

Link: https://lore.kernel.org/r/20210122023317.687987-4-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Tested-by: NSumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

Currently the allocation round_robin info is maintained by sbitmap_queue.

However, bit allocation really belongs to sbitmap. Move it there.

Link: https://lore.kernel.org/r/20210122023317.687987-3-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: virtualization@lists.linux-foundation.org
Tested-by: NSumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

__sbitmap_get_word() doesn't warp if it's starting from the beginning
(i.e. initial hint is 0). Instead of stashing the original hint just set
@wrap accordingly.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

sbitmap_deferred_clear() does CAS loop to propagate cleared bits,
replace it with equivalent atomic bitwise and. That's slightly faster
and makes wait-free instead of lock-free as before.

The atomic can be relaxed (i.e. barrier-less) because following
sbitmap_get*() deal with synchronisation, see comments in
sbitmap_queue_clear().

It's ok to cast to atomic_long_t, that's what bitops/lock.h does.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

map->swap_lock protects map->cleared from concurrent modification,
however sbitmap_deferred_clear() is already atomically drains it, so
it's guaranteed to not loose bits on concurrent
sbitmap_deferred_clear().

A one threaded tag heavy test on top of nullbk showed ~1.5% t-put
increase, and 3% -> 1% cycle reduction of sbitmap_get() according to perf.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Because of spinlocks and atomics sbitmap_deferred_clear() have to reload
&sb->map[index] on each access even though the map address won't change.
Pass in sbitmap_word instead of {sb, index}, so it's cached in a
variable. It also improves code generation of
sbitmap_find_bit_in_index().
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

sbitmap works by maintaining separate bitmaps of set and cleared bits.
The set bits are cleared in a batch, to save the burden of continuously
locking the "word" map to unset.

sbitmap_bitmap_show() only shows the set bits (in "word"), which is not
too much use, so mask out the cleared bits.

Fixes: ea86ea2c ("sbitmap: ammortize cost of clearing bits")
Signed-off-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Under heavy loads where the kyber I/O scheduler hits the token limits for
its scheduling domains, kyber can become stuck.  When active requests
complete, kyber may not be woken up leaving the I/O requests in kyber
stuck.

This stuck state is due to a race condition with kyber and the sbitmap
functions it uses to run a callback when enough requests have completed.
The running of a sbt_wait callback can race with the attempt to insert the
sbt_wait.  Since sbitmap_del_wait_queue removes the sbt_wait from the list
first then sets the sbq field to NULL, kyber can see the item as not on a
list but the call to sbitmap_add_wait_queue will see sbq as non-NULL. This
results in the sbt_wait being inserted onto the wait list but ws_active
doesn't get incremented.  So the sbitmap queue does not know there is a
waiter on a wait list.

Since sbitmap doesn't think there is a waiter, kyber may never be
informed that there are domain tokens available and the I/O never advances.
With the sbt_wait on a wait list, kyber believes it has an active waiter
so cannot insert a new waiter when reaching the domain's full state.

This race can be fixed by only adding the sbt_wait to the queue if the
sbq field is NULL.  If sbq is not NULL, there is already an action active
which will trigger the re-running of kyber.  Let it run and add the
sbt_wait to the wait list if still needing to wait.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NDavid Jeffery <djeffery@redhat.com>
Reported-by: NJohn Pittman <jpittman@redhat.com>
Tested-by: NJohn Pittman <jpittman@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Since the only caller of this function has been deleted, delete this one
also.
Signed-off-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

cmpxchg() with an immediate value could be replaced with less expensive
xchg(). The same true if new value don't _depend_ on the old one.

In the second block, atomic_cmpxchg() return value isn't checked, so
after atomic_cmpxchg() ->  atomic_xchg() conversion it could be replaced
with atomic_set(). Comparison with atomic_read() in the second chunk was
left as an optimisation (if that was the initial intention).
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license v2 as published
  by the free software foundation this program is distributed in the
  hope that it will be useful but without any warranty without even
  the implied warranty of merchantability or fitness for a particular
  purpose see the gnu general public license for more details you
  should have received a copy of the gnu general public license along
  with this program if not see https www gnu org licenses

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 2 file(s).
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NAlexios Zavras <alexios.zavras@intel.com>
Reviewed-by: NArmijn Hemel <armijn@tjaldur.nl>
Reviewed-by: NKate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: NAllison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190530000435.923873561@linutronix.deSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This barrier only applies to the read-modify-write operations; in
particular, it does not apply to the atomic_set() primitive.

Replace the barrier with an smp_mb().

Fixes: 6c0ca7ae ("sbitmap: fix wakeup hang after sbq resize")
Cc: stable@vger.kernel.org
Reported-by: N"Paul E. McKenney" <paulmck@linux.ibm.com>
Reported-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NAndrea Parri <andrea.parri@amarulasolutions.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: linux-block@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Inside sbitmap_queue_clear(), once the clear bit is set, it will be
visiable to allocation path immediately. Meantime READ/WRITE on old
associated instance(such as request in case of blk-mq) may be
out-of-order with the setting clear bit, so race with re-allocation
may be triggered.

Adds one memory barrier for ordering READ/WRITE of the freed associated
instance with setting clear bit for avoiding race with re-allocation.

The following kernel oops triggerd by block/006 on aarch64 may be fixed:

[  142.330954] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000330
[  142.338794] Mem abort info:
[  142.341554]   ESR = 0x96000005
[  142.344632]   Exception class = DABT (current EL), IL = 32 bits
[  142.350500]   SET = 0, FnV = 0
[  142.353544]   EA = 0, S1PTW = 0
[  142.356678] Data abort info:
[  142.359528]   ISV = 0, ISS = 0x00000005
[  142.363343]   CM = 0, WnR = 0
[  142.366305] user pgtable: 64k pages, 48-bit VAs, pgdp = 000000002a3c51c0
[  142.372983] [0000000000000330] pgd=0000000000000000, pud=0000000000000000
[  142.379777] Internal error: Oops: 96000005 [#1] SMP
[  142.384613] Modules linked in: null_blk ib_isert iscsi_target_mod ib_srpt target_core_mod ib_srp scsi_transport_srp vfat fat rpcrdma sunrpc rdma_ucm ib_iser rdma_cm iw_cm libiscsi ib_umad scsi_transport_iscsi ib_ipoib ib_cm mlx5_ib ib_uverbs ib_core sbsa_gwdt crct10dif_ce ghash_ce ipmi_ssif sha2_ce ipmi_devintf sha256_arm64 sg sha1_ce ipmi_msghandler ip_tables xfs libcrc32c mlx5_core sdhci_acpi mlxfw ahci_platform at803x sdhci libahci_platform qcom_emac mmc_core hdma hdma_mgmt i2c_dev [last unloaded: null_blk]
[  142.429753] CPU: 7 PID: 1983 Comm: fio Not tainted 5.0.0.cki #2
[  142.449458] pstate: 00400005 (nzcv daif +PAN -UAO)
[  142.454239] pc : __blk_mq_free_request+0x4c/0xa8
[  142.458830] lr : blk_mq_free_request+0xec/0x118
[  142.463344] sp : ffff00003360f6a0
[  142.466646] x29: ffff00003360f6a0 x28: ffff000010e70000
[  142.471941] x27: ffff801729a50048 x26: 0000000000010000
[  142.477232] x25: ffff00003360f954 x24: ffff7bdfff021440
[  142.482529] x23: 0000000000000000 x22: 00000000ffffffff
[  142.487830] x21: ffff801729810000 x20: 0000000000000000
[  142.493123] x19: ffff801729a50000 x18: 0000000000000000
[  142.498413] x17: 0000000000000000 x16: 0000000000000001
[  142.503709] x15: 00000000000000ff x14: ffff7fe000000000
[  142.509003] x13: ffff8017dcde09a0 x12: 0000000000000000
[  142.514308] x11: 0000000000000001 x10: 0000000000000008
[  142.519597] x9 : ffff8017dcde09a0 x8 : 0000000000002000
[  142.524889] x7 : ffff8017dcde0a00 x6 : 000000015388f9be
[  142.530187] x5 : 0000000000000001 x4 : 0000000000000000
[  142.535478] x3 : 0000000000000000 x2 : 0000000000000000
[  142.540777] x1 : 0000000000000001 x0 : ffff00001041b194
[  142.546071] Process fio (pid: 1983, stack limit = 0x000000006460a0ea)
[  142.552500] Call trace:
[  142.554926]  __blk_mq_free_request+0x4c/0xa8
[  142.559181]  blk_mq_free_request+0xec/0x118
[  142.563352]  blk_mq_end_request+0xfc/0x120
[  142.567444]  end_cmd+0x3c/0xa8 [null_blk]
[  142.571434]  null_complete_rq+0x20/0x30 [null_blk]
[  142.576194]  blk_mq_complete_request+0x108/0x148
[  142.580797]  null_handle_cmd+0x1d4/0x718 [null_blk]
[  142.585662]  null_queue_rq+0x60/0xa8 [null_blk]
[  142.590171]  blk_mq_try_issue_directly+0x148/0x280
[  142.594949]  blk_mq_try_issue_list_directly+0x9c/0x108
[  142.600064]  blk_mq_sched_insert_requests+0xb0/0xd0
[  142.604926]  blk_mq_flush_plug_list+0x16c/0x2a0
[  142.609441]  blk_flush_plug_list+0xec/0x118
[  142.613608]  blk_finish_plug+0x3c/0x4c
[  142.617348]  blkdev_direct_IO+0x3b4/0x428
[  142.621336]  generic_file_read_iter+0x84/0x180
[  142.625761]  blkdev_read_iter+0x50/0x78
[  142.629579]  aio_read.isra.6+0xf8/0x190
[  142.633409]  __io_submit_one.isra.8+0x148/0x738
[  142.637912]  io_submit_one.isra.9+0x88/0xb8
[  142.642078]  __arm64_sys_io_submit+0xe0/0x238
[  142.646428]  el0_svc_handler+0xa0/0x128
[  142.650238]  el0_svc+0x8/0xc
[  142.653104] Code: b9402a63 f9000a7f 3100047f 540000a0 (f9419a81)
[  142.659202] ---[ end trace 467586bc175eb09d ]---

Fixes: ea86ea2c ("sbitmap: ammortize cost of clearing bits")
Reported-and-bisected_and_tested-by: Yi Zhang <yi.zhang@redhat.com>
Cc: Yi Zhang <yi.zhang@redhat.com>
Cc: "jianchao.wang" <jianchao.w.wang@oracle.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Because we may call blk_mq_get_driver_tag() directly from
blk_mq_dispatch_rq_list() without holding any lock, then HARDIRQ may
come and the above DEADLOCK is triggered.

Commit ab53dcfb3e7b ("sbitmap: Protect swap_lock from hardirq") tries to
fix this issue by using 'spin_lock_bh', which isn't enough because we
complete request from hardirq context direclty in case of multiqueue.

Cc: Clark Williams <williams@redhat.com>
Fixes: ab53dcfb3e7b ("sbitmap: Protect swap_lock from hardirq")
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The swap_lock used by sbitmap has a chain with locks taken from softirq,
but the swap_lock is not protected from being preempted by softirqs.

A chain exists of:

 sbq->ws[i].wait -> dispatch_wait_lock -> swap_lock

Where the sbq->ws[i].wait lock can be taken from softirq context, which
means all locks below it in the chain must also be protected from
softirqs.
Reported-by: NClark Williams <williams@redhat.com>
Fixes: 58ab5e32 ("sbitmap: silence bogus lockdep IRQ warning")
Fixes: ea86ea2c ("sbitmap: amortize cost of clearing bits")
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

After commit 5d2ee712, users of sbitmap that need wait queue
handling must use the provided helpers. But we only added
prepare_to_wait()/finish_wait() style helpers, add the equivalent
add_wait_queue/list_del wrappers as we..

This is needed to ensure kyber plays by the sbitmap waitqueue
rules.
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We're missing a deferred clear off the shallow get, which can cause
a hang. Additionally, when we resize the sbitmap, we should also
flush deferred clears for good measure.

Ensure we have full coverage on batch clears, even for paths where
we would not be doing deferred clear. This makes it less error
prone for future additions.
Reported-by: NBart Van Assche <bvanassche@acm.org>
Tested-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Ming reports that lockdep spews the following trace. What this
essentially says is that the sbitmap swap_lock was used inconsistently
in IRQ enabled and disabled context, and that is usually indicative of a
bug that will cause a deadlock.

For this case, it's a false positive. The swap_lock is used from process
context only, when we swap the bits in the word and cleared mask. We
also end up doing that when we are getting a driver tag, from the
blk_mq_mark_tag_wait(), and from there we hold the waitqueue lock with
IRQs disabled. However, this isn't from an actual IRQ, it's still
process context.

In lieu of a better way to fix this, simply always disable interrupts
when grabbing the swap_lock if lockdep is enabled.

[  100.967642] ================start test sanity/001================
[  101.238280] null: module loaded
[  106.093735]
[  106.094012] =====================================================
[  106.094854] WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
[  106.095759] 4.20.0-rc3_5d2ee712_for-next+ #1 Not tainted
[  106.096551] -----------------------------------------------------
[  106.097386] fio/1043 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
[  106.098231] 000000004c43fa71
(&(&sb->map[i].swap_lock)->rlock){+.+.}, at: sbitmap_get+0xd5/0x22c
[  106.099431]
[  106.099431] and this task is already holding:
[  106.100229] 000000007eec8b2f
(&(&hctx->dispatch_wait_lock)->rlock){....}, at:
blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.101630] which would create a new lock dependency:
[  106.102326]  (&(&hctx->dispatch_wait_lock)->rlock){....} ->
(&(&sb->map[i].swap_lock)->rlock){+.+.}
[  106.103553]
[  106.103553] but this new dependency connects a SOFTIRQ-irq-safe lock:
[  106.104580]  (&sbq->ws[i].wait){..-.}
[  106.104582]
[  106.104582] ... which became SOFTIRQ-irq-safe at:
[  106.105751]   _raw_spin_lock_irqsave+0x4b/0x82
[  106.106284]   __wake_up_common_lock+0x119/0x1b9
[  106.106825]   sbitmap_queue_wake_up+0x33f/0x383
[  106.107456]   sbitmap_queue_clear+0x4c/0x9a
[  106.108046]   __blk_mq_free_request+0x188/0x1d3
[  106.108581]   blk_mq_free_request+0x23b/0x26b
[  106.109102]   scsi_end_request+0x345/0x5d7
[  106.109587]   scsi_io_completion+0x4b5/0x8f0
[  106.110099]   scsi_finish_command+0x412/0x456
[  106.110615]   scsi_softirq_done+0x23f/0x29b
[  106.111115]   blk_done_softirq+0x2a7/0x2e6
[  106.111608]   __do_softirq+0x360/0x6ad
[  106.112062]   run_ksoftirqd+0x2f/0x5b
[  106.112499]   smpboot_thread_fn+0x3a5/0x3db
[  106.113000]   kthread+0x1d4/0x1e4
[  106.113457]   ret_from_fork+0x3a/0x50
[  106.113969]
[  106.113969] to a SOFTIRQ-irq-unsafe lock:
[  106.114672]  (&(&sb->map[i].swap_lock)->rlock){+.+.}
[  106.114674]
[  106.114674] ... which became SOFTIRQ-irq-unsafe at:
[  106.116000] ...
[  106.116003]   _raw_spin_lock+0x33/0x64
[  106.116676]   sbitmap_get+0xd5/0x22c
[  106.117134]   __sbitmap_queue_get+0xe8/0x177
[  106.117731]   __blk_mq_get_tag+0x1e6/0x22d
[  106.118286]   blk_mq_get_tag+0x1db/0x6e4
[  106.118756]   blk_mq_get_driver_tag+0x161/0x258
[  106.119383]   blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.120043]   blk_mq_do_dispatch_sched+0x23a/0x287
[  106.120607]   blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.121234]   __blk_mq_run_hw_queue+0x137/0x17e
[  106.121781]   __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.122366]   blk_mq_run_hw_queue+0x151/0x187
[  106.122887]   blk_mq_sched_insert_requests+0x13f/0x175
[  106.123492]   blk_mq_flush_plug_list+0x7d6/0x81b
[  106.124042]   blk_flush_plug_list+0x392/0x3d7
[  106.124557]   blk_finish_plug+0x37/0x4f
[  106.125019]   read_pages+0x3ef/0x430
[  106.125446]   __do_page_cache_readahead+0x18e/0x2fc
[  106.126027]   force_page_cache_readahead+0x121/0x133
[  106.126621]   page_cache_sync_readahead+0x35f/0x3bb
[  106.127229]   generic_file_buffered_read+0x410/0x1860
[  106.127932]   __vfs_read+0x319/0x38f
[  106.128415]   vfs_read+0xd2/0x19a
[  106.128817]   ksys_read+0xb9/0x135
[  106.129225]   do_syscall_64+0x140/0x385
[  106.129684]   entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.130292]
[  106.130292] other info that might help us debug this:
[  106.130292]
[  106.131226] Chain exists of:
[  106.131226]   &sbq->ws[i].wait -->
&(&hctx->dispatch_wait_lock)->rlock -->
&(&sb->map[i].swap_lock)->rlock
[  106.131226]
[  106.132865]  Possible interrupt unsafe locking scenario:
[  106.132865]
[  106.133659]        CPU0                    CPU1
[  106.134194]        ----                    ----
[  106.134733]   lock(&(&sb->map[i].swap_lock)->rlock);
[  106.135318]                                local_irq_disable();
[  106.136014]                                lock(&sbq->ws[i].wait);
[  106.136747]
lock(&(&hctx->dispatch_wait_lock)->rlock);
[  106.137742]   <Interrupt>
[  106.138110]     lock(&sbq->ws[i].wait);
[  106.138625]
[  106.138625]  *** DEADLOCK ***
[  106.138625]
[  106.139430] 3 locks held by fio/1043:
[  106.139947]  #0: 0000000076ff0fd9 (rcu_read_lock){....}, at:
hctx_lock+0x29/0xe8
[  106.140813]  #1: 000000002feb1016 (&sbq->ws[i].wait){..-.}, at:
blk_mq_dispatch_rq_list+0x4ad/0xd7c
[  106.141877]  #2: 000000007eec8b2f
(&(&hctx->dispatch_wait_lock)->rlock){....}, at:
blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.143267]
[  106.143267] the dependencies between SOFTIRQ-irq-safe lock and the
holding lock:
[  106.144351]  -> (&sbq->ws[i].wait){..-.} ops: 82 {
[  106.144926]     IN-SOFTIRQ-W at:
[  106.145314]                       _raw_spin_lock_irqsave+0x4b/0x82
[  106.146042]                       __wake_up_common_lock+0x119/0x1b9
[  106.146785]                       sbitmap_queue_wake_up+0x33f/0x383
[  106.147567]                       sbitmap_queue_clear+0x4c/0x9a
[  106.148379]                       __blk_mq_free_request+0x188/0x1d3
[  106.149148]                       blk_mq_free_request+0x23b/0x26b
[  106.149864]                       scsi_end_request+0x345/0x5d7
[  106.150546]                       scsi_io_completion+0x4b5/0x8f0
[  106.151367]                       scsi_finish_command+0x412/0x456
[  106.152157]                       scsi_softirq_done+0x23f/0x29b
[  106.152855]                       blk_done_softirq+0x2a7/0x2e6
[  106.153537]                       __do_softirq+0x360/0x6ad
[  106.154280]                       run_ksoftirqd+0x2f/0x5b
[  106.155020]                       smpboot_thread_fn+0x3a5/0x3db
[  106.155828]                       kthread+0x1d4/0x1e4
[  106.156526]                       ret_from_fork+0x3a/0x50
[  106.157267]     INITIAL USE at:
[  106.157713]                      _raw_spin_lock_irqsave+0x4b/0x82
[  106.158542]                      prepare_to_wait_exclusive+0xa8/0x215
[  106.159421]                      blk_mq_get_tag+0x34f/0x6e4
[  106.160186]                      blk_mq_get_request+0x48e/0xaef
[  106.160997]                      blk_mq_make_request+0x27e/0xbd2
[  106.161828]                      generic_make_request+0x4d1/0x873
[  106.162661]                      submit_bio+0x20c/0x253
[  106.163379]                      mpage_bio_submit+0x44/0x4b
[  106.164142]                      mpage_readpages+0x3c2/0x407
[  106.164919]                      read_pages+0x13a/0x430
[  106.165633]                      __do_page_cache_readahead+0x18e/0x2fc
[  106.166530]                      force_page_cache_readahead+0x121/0x133
[  106.167439]                      page_cache_sync_readahead+0x35f/0x3bb
[  106.168337]                      generic_file_buffered_read+0x410/0x1860
[  106.169255]                      __vfs_read+0x319/0x38f
[  106.169977]                      vfs_read+0xd2/0x19a
[  106.170662]                      ksys_read+0xb9/0x135
[  106.171356]                      do_syscall_64+0x140/0x385
[  106.172120]                      entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.173051]   }
[  106.173308]   ... key      at: [<ffffffff85094600>] __key.26481+0x0/0x40
[  106.174219]   ... acquired at:
[  106.174646]    _raw_spin_lock+0x33/0x64
[  106.175183]    blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.175843]    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.176518]    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.177262]    __blk_mq_run_hw_queue+0x137/0x17e
[  106.177900]    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.178591]    blk_mq_run_hw_queue+0x151/0x187
[  106.179207]    blk_mq_sched_insert_requests+0x13f/0x175
[  106.179926]    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.180571]    blk_flush_plug_list+0x392/0x3d7
[  106.181187]    blk_finish_plug+0x37/0x4f
[  106.181737]    __se_sys_io_submit+0x171/0x304
[  106.182346]    do_syscall_64+0x140/0x385
[  106.182895]    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.183607]
[  106.183830] -> (&(&hctx->dispatch_wait_lock)->rlock){....} ops: 1 {
[  106.184691]    INITIAL USE at:
[  106.185119]                    _raw_spin_lock+0x33/0x64
[  106.185838]                    blk_mq_dispatch_rq_list+0x4c1/0xd7c
[  106.186697]                    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.187551]                    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.188481]                    __blk_mq_run_hw_queue+0x137/0x17e
[  106.189307]                    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.190189]                    blk_mq_run_hw_queue+0x151/0x187
[  106.190989]                    blk_mq_sched_insert_requests+0x13f/0x175
[  106.191902]                    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.192739]                    blk_flush_plug_list+0x392/0x3d7
[  106.193535]                    blk_finish_plug+0x37/0x4f
[  106.194269]                    __se_sys_io_submit+0x171/0x304
[  106.195059]                    do_syscall_64+0x140/0x385
[  106.195794]                    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.196705]  }
[  106.196950]  ... key      at: [<ffffffff84880620>] __key.51231+0x0/0x40
[  106.197853]  ... acquired at:
[  106.198270]    lock_acquire+0x280/0x2f3
[  106.198806]    _raw_spin_lock+0x33/0x64
[  106.199337]    sbitmap_get+0xd5/0x22c
[  106.199850]    __sbitmap_queue_get+0xe8/0x177
[  106.200450]    __blk_mq_get_tag+0x1e6/0x22d
[  106.201035]    blk_mq_get_tag+0x1db/0x6e4
[  106.201589]    blk_mq_get_driver_tag+0x161/0x258
[  106.202237]    blk_mq_dispatch_rq_list+0x5b9/0xd7c
[  106.202902]    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.203572]    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.204316]    __blk_mq_run_hw_queue+0x137/0x17e
[  106.204956]    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.205649]    blk_mq_run_hw_queue+0x151/0x187
[  106.206269]    blk_mq_sched_insert_requests+0x13f/0x175
[  106.206997]    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.207644]    blk_flush_plug_list+0x392/0x3d7
[  106.208264]    blk_finish_plug+0x37/0x4f
[  106.208814]    __se_sys_io_submit+0x171/0x304
[  106.209415]    do_syscall_64+0x140/0x385
[  106.209965]    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.210684]
[  106.210904]
[  106.210904] the dependencies between the lock to be acquired
[  106.210905]  and SOFTIRQ-irq-unsafe lock:
[  106.212541] -> (&(&sb->map[i].swap_lock)->rlock){+.+.} ops: 1969 {
[  106.213393]    HARDIRQ-ON-W at:
[  106.213840]                     _raw_spin_lock+0x33/0x64
[  106.214570]                     sbitmap_get+0xd5/0x22c
[  106.215282]                     __sbitmap_queue_get+0xe8/0x177
[  106.216086]                     __blk_mq_get_tag+0x1e6/0x22d
[  106.216876]                     blk_mq_get_tag+0x1db/0x6e4
[  106.217627]                     blk_mq_get_driver_tag+0x161/0x258
[  106.218465]                     blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.219326]                     blk_mq_do_dispatch_sched+0x23a/0x287
[  106.220198]                     blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.221138]                     __blk_mq_run_hw_queue+0x137/0x17e
[  106.221975]                     __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.222874]                     blk_mq_run_hw_queue+0x151/0x187
[  106.223686]                     blk_mq_sched_insert_requests+0x13f/0x175
[  106.224597]                     blk_mq_flush_plug_list+0x7d6/0x81b
[  106.225444]                     blk_flush_plug_list+0x392/0x3d7
[  106.226255]                     blk_finish_plug+0x37/0x4f
[  106.227006]                     read_pages+0x3ef/0x430
[  106.227717]                     __do_page_cache_readahead+0x18e/0x2fc
[  106.228595]                     force_page_cache_readahead+0x121/0x133
[  106.229491]                     page_cache_sync_readahead+0x35f/0x3bb
[  106.230373]                     generic_file_buffered_read+0x410/0x1860
[  106.231277]                     __vfs_read+0x319/0x38f
[  106.231986]                     vfs_read+0xd2/0x19a
[  106.232666]                     ksys_read+0xb9/0x135
[  106.233350]                     do_syscall_64+0x140/0x385
[  106.234097]                     entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.235012]    SOFTIRQ-ON-W at:
[  106.235460]                     _raw_spin_lock+0x33/0x64
[  106.236195]                     sbitmap_get+0xd5/0x22c
[  106.236913]                     __sbitmap_queue_get+0xe8/0x177
[  106.237715]                     __blk_mq_get_tag+0x1e6/0x22d
[  106.238488]                     blk_mq_get_tag+0x1db/0x6e4
[  106.239244]                     blk_mq_get_driver_tag+0x161/0x258
[  106.240079]                     blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.240937]                     blk_mq_do_dispatch_sched+0x23a/0x287
[  106.241806]                     blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.242751]                     __blk_mq_run_hw_queue+0x137/0x17e
[  106.243579]                     __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.244469]                     blk_mq_run_hw_queue+0x151/0x187
[  106.245277]                     blk_mq_sched_insert_requests+0x13f/0x175
[  106.246191]                     blk_mq_flush_plug_list+0x7d6/0x81b
[  106.247044]                     blk_flush_plug_list+0x392/0x3d7
[  106.247859]                     blk_finish_plug+0x37/0x4f
[  106.248749]                     read_pages+0x3ef/0x430
[  106.249463]                     __do_page_cache_readahead+0x18e/0x2fc
[  106.250357]                     force_page_cache_readahead+0x121/0x133
[  106.251263]                     page_cache_sync_readahead+0x35f/0x3bb
[  106.252157]                     generic_file_buffered_read+0x410/0x1860
[  106.253084]                     __vfs_read+0x319/0x38f
[  106.253808]                     vfs_read+0xd2/0x19a
[  106.254488]                     ksys_read+0xb9/0x135
[  106.255186]                     do_syscall_64+0x140/0x385
[  106.255943]                     entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.256867]    INITIAL USE at:
[  106.257300]                    _raw_spin_lock+0x33/0x64
[  106.258033]                    sbitmap_get+0xd5/0x22c
[  106.258747]                    __sbitmap_queue_get+0xe8/0x177
[  106.259542]                    __blk_mq_get_tag+0x1e6/0x22d
[  106.260320]                    blk_mq_get_tag+0x1db/0x6e4
[  106.261072]                    blk_mq_get_driver_tag+0x161/0x258
[  106.261902]                    blk_mq_dispatch_rq_list+0x28e/0xd7c
[  106.262762]                    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.263626]                    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.264571]                    __blk_mq_run_hw_queue+0x137/0x17e
[  106.265409]                    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.266302]                    blk_mq_run_hw_queue+0x151/0x187
[  106.267111]                    blk_mq_sched_insert_requests+0x13f/0x175
[  106.268028]                    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.268878]                    blk_flush_plug_list+0x392/0x3d7
[  106.269694]                    blk_finish_plug+0x37/0x4f
[  106.270432]                    read_pages+0x3ef/0x430
[  106.271139]                    __do_page_cache_readahead+0x18e/0x2fc
[  106.272040]                    force_page_cache_readahead+0x121/0x133
[  106.272932]                    page_cache_sync_readahead+0x35f/0x3bb
[  106.273811]                    generic_file_buffered_read+0x410/0x1860
[  106.274709]                    __vfs_read+0x319/0x38f
[  106.275407]                    vfs_read+0xd2/0x19a
[  106.276074]                    ksys_read+0xb9/0x135
[  106.276764]                    do_syscall_64+0x140/0x385
[  106.277500]                    entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  106.278417]  }
[  106.278676]  ... key      at: [<ffffffff85094640>] __key.26212+0x0/0x40
[  106.279586]  ... acquired at:
[  106.280026]    lock_acquire+0x280/0x2f3
[  106.280559]    _raw_spin_lock+0x33/0x64
[  106.281101]    sbitmap_get+0xd5/0x22c
[  106.281610]    __sbitmap_queue_get+0xe8/0x177
[  106.282221]    __blk_mq_get_tag+0x1e6/0x22d
[  106.282809]    blk_mq_get_tag+0x1db/0x6e4
[  106.283368]    blk_mq_get_driver_tag+0x161/0x258
[  106.284018]    blk_mq_dispatch_rq_list+0x5b9/0xd7c
[  106.284685]    blk_mq_do_dispatch_sched+0x23a/0x287
[  106.285371]    blk_mq_sched_dispatch_requests+0x379/0x3fc
[  106.286135]    __blk_mq_run_hw_queue+0x137/0x17e
[  106.286806]    __blk_mq_delay_run_hw_queue+0x80/0x25f
[  106.287515]    blk_mq_run_hw_queue+0x151/0x187
[  106.288149]    blk_mq_sched_insert_requests+0x13f/0x175
[  106.289041]    blk_mq_flush_plug_list+0x7d6/0x81b
[  106.289912]    blk_flush_plug_list+0x392/0x3d7
[  106.290590]    blk_finish_plug+0x37/0x4f
[  106.291238]    __se_sys_io_submit+0x171/0x304
[  106.291864]    do_syscall_64+0x140/0x385
[  106.292534]    entry_SYSCALL_64_after_hwframe+0x49/0xbe
Reported-by: NMing Lei <ming.lei@redhat.com>
Tested-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Even if we have no waiters on any of the sbitmap_queue wait states, we
still have to loop every entry to check. We do this for every IO, so
the cost adds up.

Shift a bit of the cost to the slow path, when we actually have waiters.
Wrap prepare_to_wait_exclusive() and finish_wait(), so we can maintain
an internal count of how many are currently active. Then we can simply
check this count in sbq_wake_ptr() and not have to loop if we don't
have any sleepers.

Convert the two users of sbitmap with waiting, blk-mq-tag and iSCSI.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

sbitmap maintains a set of words that we use to set and clear bits, with
each bit representing a tag for blk-mq. Even though we spread the bits
out and maintain a hint cache, one particular bit allocated will end up
being cleared in the exact same spot.

This introduces batched clearing of bits. Instead of clearing a given
bit, the same bit is set in a cleared/free mask instead. If we fail
allocating a bit from a given word, then we check the free mask, and
batch move those cleared bits at that time. This trades 64 atomic bitops
for 2 cmpxchg().

In a threaded poll test case, half the overhead of getting and clearing
tags is removed with this change. On another poll test case with a
single thread, performance is unchanged.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we aren't forced to do round robin tag allocation, just use the
allocation hint to find the index for the tag word, don't use it for the
offset inside the word. This avoids a potential extra round trip in the
bit looping, and since we're fetching this cacheline, we may as well
check the whole word from the start.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The kzalloc_node() function has a 2-factor argument form, kcalloc_node(). This
patch replaces cases of:

        kzalloc_node(a * b, gfp, node)

with:
        kcalloc_node(a * b, gfp, node)

as well as handling cases of:

        kzalloc_node(a * b * c, gfp, node)

with:

        kzalloc_node(array3_size(a, b, c), gfp, node)

as it's slightly less ugly than:

        kcalloc_node(array_size(a, b), c, gfp, node)

This does, however, attempt to ignore constant size factors like:

        kzalloc_node(4 * 1024, gfp, node)

though any constants defined via macros get caught up in the conversion.

Any factors with a sizeof() of "unsigned char", "char", and "u8" were
dropped, since they're redundant.

The Coccinelle script used for this was:

// Fix redundant parens around sizeof().
@@
type TYPE;
expression THING, E;
@@

(
  kzalloc_node(
-	(sizeof(TYPE)) * E
+	sizeof(TYPE) * E
  , ...)
|
  kzalloc_node(
-	(sizeof(THING)) * E
+	sizeof(THING) * E
  , ...)
)

// Drop single-byte sizes and redundant parens.
@@
expression COUNT;
typedef u8;
typedef __u8;
@@

(
  kzalloc_node(
-	sizeof(u8) * (COUNT)
+	COUNT
  , ...)
|
  kzalloc_node(
-	sizeof(__u8) * (COUNT)
+	COUNT
  , ...)
|
  kzalloc_node(
-	sizeof(char) * (COUNT)
+	COUNT
  , ...)
|
  kzalloc_node(
-	sizeof(unsigned char) * (COUNT)
+	COUNT
  , ...)
|
  kzalloc_node(
-	sizeof(u8) * COUNT
+	COUNT
  , ...)
|
  kzalloc_node(
-	sizeof(__u8) * COUNT
+	COUNT
  , ...)
|
  kzalloc_node(
-	sizeof(char) * COUNT
+	COUNT
  , ...)
|
  kzalloc_node(
-	sizeof(unsigned char) * COUNT
+	COUNT
  , ...)
)

// 2-factor product with sizeof(type/expression) and identifier or constant.
@@
type TYPE;
expression THING;
identifier COUNT_ID;
constant COUNT_CONST;
@@

(
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(TYPE) * (COUNT_ID)
+	COUNT_ID, sizeof(TYPE)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(TYPE) * COUNT_ID
+	COUNT_ID, sizeof(TYPE)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(TYPE) * (COUNT_CONST)
+	COUNT_CONST, sizeof(TYPE)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(TYPE) * COUNT_CONST
+	COUNT_CONST, sizeof(TYPE)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(THING) * (COUNT_ID)
+	COUNT_ID, sizeof(THING)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(THING) * COUNT_ID
+	COUNT_ID, sizeof(THING)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(THING) * (COUNT_CONST)
+	COUNT_CONST, sizeof(THING)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(THING) * COUNT_CONST
+	COUNT_CONST, sizeof(THING)
  , ...)
)

// 2-factor product, only identifiers.
@@
identifier SIZE, COUNT;
@@

- kzalloc_node
+ kcalloc_node
  (
-	SIZE * COUNT
+	COUNT, SIZE
  , ...)

// 3-factor product with 1 sizeof(type) or sizeof(expression), with
// redundant parens removed.
@@
expression THING;
identifier STRIDE, COUNT;
type TYPE;
@@

(
  kzalloc_node(
-	sizeof(TYPE) * (COUNT) * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  kzalloc_node(
-	sizeof(TYPE) * (COUNT) * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  kzalloc_node(
-	sizeof(TYPE) * COUNT * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  kzalloc_node(
-	sizeof(TYPE) * COUNT * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  kzalloc_node(
-	sizeof(THING) * (COUNT) * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
|
  kzalloc_node(
-	sizeof(THING) * (COUNT) * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
|
  kzalloc_node(
-	sizeof(THING) * COUNT * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
|
  kzalloc_node(
-	sizeof(THING) * COUNT * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
)

// 3-factor product with 2 sizeof(variable), with redundant parens removed.
@@
expression THING1, THING2;
identifier COUNT;
type TYPE1, TYPE2;
@@

(
  kzalloc_node(
-	sizeof(TYPE1) * sizeof(TYPE2) * COUNT
+	array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2))
  , ...)
|
  kzalloc_node(
-	sizeof(TYPE1) * sizeof(THING2) * (COUNT)
+	array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2))
  , ...)
|
  kzalloc_node(
-	sizeof(THING1) * sizeof(THING2) * COUNT
+	array3_size(COUNT, sizeof(THING1), sizeof(THING2))
  , ...)
|
  kzalloc_node(
-	sizeof(THING1) * sizeof(THING2) * (COUNT)
+	array3_size(COUNT, sizeof(THING1), sizeof(THING2))
  , ...)
|
  kzalloc_node(
-	sizeof(TYPE1) * sizeof(THING2) * COUNT
+	array3_size(COUNT, sizeof(TYPE1), sizeof(THING2))
  , ...)
|
  kzalloc_node(
-	sizeof(TYPE1) * sizeof(THING2) * (COUNT)
+	array3_size(COUNT, sizeof(TYPE1), sizeof(THING2))
  , ...)
)

// 3-factor product, only identifiers, with redundant parens removed.
@@
identifier STRIDE, SIZE, COUNT;
@@

(
  kzalloc_node(
-	(COUNT) * STRIDE * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  kzalloc_node(
-	COUNT * (STRIDE) * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  kzalloc_node(
-	COUNT * STRIDE * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  kzalloc_node(
-	(COUNT) * (STRIDE) * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  kzalloc_node(
-	COUNT * (STRIDE) * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  kzalloc_node(
-	(COUNT) * STRIDE * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  kzalloc_node(
-	(COUNT) * (STRIDE) * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  kzalloc_node(
-	COUNT * STRIDE * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
)

// Any remaining multi-factor products, first at least 3-factor products,
// when they're not all constants...
@@
expression E1, E2, E3;
constant C1, C2, C3;
@@

(
  kzalloc_node(C1 * C2 * C3, ...)
|
  kzalloc_node(
-	(E1) * E2 * E3
+	array3_size(E1, E2, E3)
  , ...)
|
  kzalloc_node(
-	(E1) * (E2) * E3
+	array3_size(E1, E2, E3)
  , ...)
|
  kzalloc_node(
-	(E1) * (E2) * (E3)
+	array3_size(E1, E2, E3)
  , ...)
|
  kzalloc_node(
-	E1 * E2 * E3
+	array3_size(E1, E2, E3)
  , ...)
)

// And then all remaining 2 factors products when they're not all constants,
// keeping sizeof() as the second factor argument.
@@
expression THING, E1, E2;
type TYPE;
constant C1, C2, C3;
@@

(
  kzalloc_node(sizeof(THING) * C2, ...)
|
  kzalloc_node(sizeof(TYPE) * C2, ...)
|
  kzalloc_node(C1 * C2 * C3, ...)
|
  kzalloc_node(C1 * C2, ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(TYPE) * (E2)
+	E2, sizeof(TYPE)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(TYPE) * E2
+	E2, sizeof(TYPE)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(THING) * (E2)
+	E2, sizeof(THING)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	sizeof(THING) * E2
+	E2, sizeof(THING)
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	(E1) * E2
+	E1, E2
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	(E1) * (E2)
+	E1, E2
  , ...)
|
- kzalloc_node
+ kcalloc_node
  (
-	E1 * E2
+	E1, E2
  , ...)
)
Signed-off-by: NKees Cook <keescook@chromium.org>

When the allocation process is scheduled back and the mapped hw queue is
changed, fake one extra wake up on previous queue for compensating wake
up miss, so other allocations on the previous queue won't be starved.

This patch fixes one request allocation hang issue, which can be
triggered easily in case of very low nr_request.

The race is as follows:

1) 2 hw queues, nr_requests are 2, and wake_batch is one

2) there are 3 waiters on hw queue 0

3) two in-flight requests in hw queue 0 are completed, and only two
   waiters of 3 are waken up because of wake_batch, but both the two
   waiters can be scheduled to another CPU and cause to switch to hw
   queue 1

4) then the 3rd waiter will wait for ever, since no in-flight request
   is in hw queue 0 any more.

5) this patch fixes it by the fake wakeup when waiter is scheduled to
   another hw queue

Cc: <stable@vger.kernel.org>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>

Modified commit message to make it clearer, and make it apply on
top of the 4.18 branch.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we have multiple callers of sbq_wake_up(), we can end up in a
situation where the wait_cnt will continually go more and more
negative. Consider the case where our wake batch is 1, hence
wait_cnt will start out as 1.

wait_cnt == 1

CPU0				CPU1
atomic_dec_return(), cnt == 0
				atomic_dec_return(), cnt == -1
				cmpxchg(-1, 0) (succeeds)
				[wait_cnt now 0]
cmpxchg(0, 1) (fails)

This ends up with wait_cnt being 0, we'll wakeup immediately
next time. Going through the same loop as above again, and
we'll have wait_cnt -1.

For the case where we have a larger wake batch, the only
difference is that the starting point will be higher. We'll
still end up with continually smaller batch wakeups, which
defeats the purpose of the rolling wakeups.

Always reset the wait_cnt to the batch value. Then it doesn't
matter who wins the race. But ensure that whomever does win
the race is the one that increments the ws index and wakes up
our batch count, loser gets to call __sbq_wake_up() again to
account his wakeups towards the next active wait state index.

Fixes: 6c0ca7ae ("sbitmap: fix wakeup hang after sbq resize")
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Make sure the user passed the right value to
sbitmap_queue_min_shallow_depth().
Acked-by: NPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The sbitmap queue wake batch is calculated such that once allocations
start blocking, all of the bits which are already allocated must be
enough to fulfill the batch counters of all of the waitqueues. However,
the shallow allocation depth can break this invariant, since we block
before our full depth is being utilized. Add
sbitmap_queue_min_shallow_depth(), which saves the minimum shallow depth
the sbq will use, and update sbq_calc_wake_batch() to take it into
account.
Acked-by: NPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

sbitmap_queue_get()/sbitmap_queue_clear() are used for
allocating/freeing a resource, so they should provide acquire/release
barrier semantics, respectively. sbitmap_get() currently contains a full
barrier, which is unnecessary, so use test_and_set_bit_lock() instead of
test_and_set_bit() (these are equivalent on x86_64). sbitmap_clear_bit()
does not imply any barriers, which is incorrect, as accesses of the
resource (e.g., request) could potentially get reordered to after the
clear_bit(). Introduce sbitmap_clear_bit_unlock() and use it for
sbitmap_queue_clear() (this only adds a compiler barrier on x86_64). The
other existing user of sbitmap_clear_bit() (the blk-mq software queue
pending map) is serialized through a spinlock and does not need this.
Reported-by: NTejun Heo <tj@kernel.org>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>