In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Addresses-Coverity-ID: 1056543 ("Missing break in switch")
Addresses-Coverity-ID: 1056544 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Several block drivers call alloc_disk() followed by put_disk() if
something fails before device_add_disk() is called without calling
blk_cleanup_queue(). Make sure that also for this scenario a request
queue is dissociated from the cgroup controller. This patch avoids
that loading the parport_pc, paride and pf drivers triggers the
following kernel crash:

BUG: KASAN: null-ptr-deref in pi_init+0x42e/0x580 [paride]
Read of size 4 at addr 0000000000000008 by task modprobe/744
Call Trace:
dump_stack+0x9a/0xeb
kasan_report+0x139/0x350
pi_init+0x42e/0x580 [paride]
pf_init+0x2bb/0x1000 [pf]
do_one_initcall+0x8e/0x405
do_init_module+0xd9/0x2f2
load_module+0x3ab4/0x4700
SYSC_finit_module+0x176/0x1a0
do_syscall_64+0xee/0x2b0
entry_SYSCALL_64_after_hwframe+0x42/0xb7
Reported-by: Alexandru Moise <00moses.alexander00@gmail.com>
Fixes: a063057d ("block: Fix a race between request queue removal and the block cgroup controller") # v4.17
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Tested-by: Alexandru Moise <00moses.alexander00@gmail.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Alexandru Moise <00moses.alexander00@gmail.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch does not change any functionality.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Alexandru Moise <00moses.alexander00@gmail.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This new function will be used in a later patch to verify whether a
queue has been dissociated from the cgroup controller before being
released.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Alexandru Moise <00moses.alexander00@gmail.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Commit 12f5b931 ("blk-mq: Remove generation seqeunce") removed the
only seqcount_t and u64_stats_sync instances from <linux/blkdev.h> but
did not remove the corresponding #include directives. Since these
include directives are no longer needed, remove them.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Hannes Reinecke <hare@suse.com>,
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Currently, we count the hctx as active after allocate driver tag
successfully. If a previously inactive hctx try to get tag first
time, it may fails and need to wait. However, due to the stale tag
->active_queues, the other shared-tags users are still able to
occupy all driver tags while there is someone waiting for tag.
Consequently, even if the previously inactive hctx is waked up, it
still may not be able to get a tag and could be starved.

To fix it, we count the hctx as active before try to allocate driver
tag, then when it is waiting the tag, the other shared-tag users
will reserve budget for it.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

In commit ed996a52 ("block: simplify and cleanup bvec pool
handling"), the value of the slab index is incremented by one in
bvec_alloc() after the allocation is done to indicate an index value of
0 does not need to be later freed.

bvec_nr_vecs() was not updated accordingly, and thus returns the wrong
value.  Decrement idx before performing the lookup.

Fixes: ed996a52 ("block: simplify and cleanup bvec pool handling")
Signed-off-by: Greg Edwards <gedwards@ddn.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull NVMe updates from Christoph:

"This should be the last round of NVMe updates before the 4.19 merge
 window opens.  It conatins support for write protected (aka read-only)
 namespaces from Chaitanya, two ANA fixes from Hannes and a fabrics
 fix from Tal Shorer."

* 'nvme-4.19' of git://git.infradead.org/nvme:
  nvme-fabrics: fix ctrl_loss_tmo < 0 to reconnect forever
  nvmet: add ns write protect support
  nvme: set gendisk read only based on nsattr
  nvme.h: add support for ns write protect definitions
  nvme.h: fixup ANA group descriptor format
  nvme: fixup crash on failed discovery

Remove the tailing backslash in macro BTREE_FLAG in btree.h
Signed-off-by: Shenghui Wang <shhuiw@foxmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The pr_err statement in the code for sysfs_attatch section would run
for various error codes, which maybe confusing.

E.g,

Run the command twice:
   echo 796b5c05-b03c-4bc7-9cbd-a8df5e8be891 > \
				/sys/block/bcache0/bcache/attach
   [the backing dev got attached on the first run]
   echo 796b5c05-b03c-4bc7-9cbd-a8df5e8be891 > \
				/sys/block/bcache0/bcache/attach

In dmesg, after the command run twice, we can get:
	bcache: bch_cached_dev_attach() Can't attach sda6: already attached
	bcache: __cached_dev_store() Can't attach 796b5c05-b03c-4bc7-9cbd-\
a8df5e8be891
               : cache set not found
The first statement in the message was right, but the second was
confusing.

bch_cached_dev_attach has various pr_ statements for various error
codes, except ENOENT.

After the change, rerun above command twice:
	echo 796b5c05-b03c-4bc7-9cbd-a8df5e8be891 > \
			/sys/block/bcache0/bcache/attach
	echo 796b5c05-b03c-4bc7-9cbd-a8df5e8be891 > \
			/sys/block/bcache0/bcache/attach

In dmesg we only got:
	bcache: bch_cached_dev_attach() Can't attach sda6: already attached
No confusing "cache set not found" message anymore.

And for some not exist SET-UUID:
	echo 796b5c05-b03c-4bc7-9cbd-a8df5e8be898 > \
			/sys/block/bcache0/bcache/attach
In dmesg we can get:
	bcache: __cached_dev_store() Can't attach 796b5c05-b03c-4bc7-9cbd-\
a8df5e8be898
	               : cache set not found
Signed-off-by: Shenghui Wang <shhuiw@foxmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Commit b1092c9a ("bcache: allow quick writeback when backing idle")
allows the writeback rate to be faster if there is no I/O request on a
bcache device. It works well if there is only one bcache device attached
to the cache set. If there are many bcache devices attached to a cache
set, it may introduce performance regression because multiple faster
writeback threads of the idle bcache devices will compete the btree level
locks with the bcache device who have I/O requests coming.

This patch fixes the above issue by only permitting fast writebac when
all bcache devices attached on the cache set are idle. And if one of the
bcache devices has new I/O request coming, minimized all writeback
throughput immediately and let PI controller __update_writeback_rate()
to decide the upcoming writeback rate for each bcache device.

Also when all bcache devices are idle, limited wrieback rate to a small
number is wast of thoughput, especially when backing devices are slower
non-rotation devices (e.g. SATA SSD). This patch sets a max writeback
rate for each backing device if the whole cache set is idle. A faster
writeback rate in idle time means new I/Os may have more available space
for dirty data, and people may observe a better write performance then.

Please note bcache may change its cache mode in run time, and this patch
still works if the cache mode is switched from writeback mode and there
is still dirty data on cache.

Fixes: Commit b1092c9a ("bcache: allow quick writeback when backing idle")
Cc: stable@vger.kernel.org #4.16+
Signed-off-by: Coly Li <colyli@suse.de>
Tested-by: Kai Krakow <kai@kaishome.de>
Tested-by: Stefan Priebe <s.priebe@profihost.ag>
Cc: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch tries to add code comments in bset.c, to make some
tricky code and designment to be more comprehensible. Most information
of this patch comes from the discussion between Kent and I, he
offers very informative details. If there is any mistake
of the idea behind the code, no doubt that's from me misrepresentation.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch updates code comment in bch_keylist_realloc() by fixing
incorrected function names, to make the code to be more comprehennsible.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch updates the code comment in struct cache with correct array
names, to make the code to be more comprehensible.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch adds a line of code comment in super.c:register_bdev(), to
make code to be more comprehensible.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

In bch_btree_node_get() the read-in btree node will be partially
prefetched into L1 cache for following bset iteration (if there is).
But if the btree node read is failed, the perfetch operations will
waste L1 cache space. This patch checkes whether read operation and
only does cache prefetch when read I/O succeeded.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

When writeback is not running, writeback rate should be 0, other value is
misleading. And the following dyanmic writeback rate debug parameters
should be 0 too,
	rate, proportional, integral, change
otherwise they are misleading when writeback is not running.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Greg KH suggests that normal code should not care about debugfs. Therefore
no matter successful or failed of debugfs_create_dir() execution, it is
unncessary to check its return value.

There are two functions called debugfs_create_dir() and check the return
value, which are bch_debug_init() and closure_debug_init(). This patch
changes these two functions from int to void type, and ignore return values
of debugfs_create_dir().

This patch does not fix exact bug, just makes things work as they should.
Signed-off-by: Coly Li <colyli@suse.de>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
Cc: Kai Krakow <kai@kaishome.de>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

kmem_cache_destroy has taken null pointer into account. So it is
safe to drop the null check before calling the function.
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

mempool_destroy has taken the null pointer into account. So it is safe
to remove the null check.
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

debugfs_remove_recursive has taken null pointer into account. So it is
safe to drop the null check before calling the function.
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

When the user supplies a ctrl_loss_tmo < 0, we warn them that this will
cause the fabrics layer to attempt reconnection forever.  However, in
reality the fabrics layer never attempts to reconnect because the
condition to test whether we should reconnect is backwards in this case.
Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

This patch implements the Namespace Write Protect feature described in
"NVMe TP 4005a Namespace Write Protect". In this version, we implement
No Write Protect and Write Protect states for target ns which can be
toggled by set-features commands from the host side.

For write-protect state transition, we need to flush the ns specified
as a part of command so we also add helpers for carrying out synchronous
flush operations.
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
[hch: fixed an incorrect endianess conversion, minor cleanups]
Signed-off-by: Christoph Hellwig <hch@lst.de>

NVMe 1.3 TP 4005 introduces new filed (NSATTR). This field indicates
whether given namespace is write protected or not. This patch sets the
gendisk associated with the namespace to read only based on the identify
namespace nsattr field.
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Add various definitions from NVMe 1.3 TP 4005.
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

ANA Phase 3 draft had the 'reserved' field in the group descriptor
format set to '23:17' (so that the first namespace identifier started
at byte 24), but that got move with the approved TP to '31:17'
(so that the first namespace identifier started at byte 32).
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

This patch does not change any functionality but avoids that gcc
reports the following warnings when building with W=1:

block/cfq-iosched.c: In function ?cfq_back_seek_max_store?:
block/cfq-iosched.c:4741:13: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (__data < (MIN))      \
             ^
block/cfq-iosched.c:4756:1: note: in expansion of macro ?STORE_FUNCTION?
 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
 ^~~~~~~~~~~~~~
block/cfq-iosched.c: In function ?cfq_slice_idle_store?:
block/cfq-iosched.c:4741:13: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (__data < (MIN))      \
             ^
block/cfq-iosched.c:4759:1: note: in expansion of macro ?STORE_FUNCTION?
 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
 ^~~~~~~~~~~~~~
block/cfq-iosched.c: In function ?cfq_group_idle_store?:
block/cfq-iosched.c:4741:13: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (__data < (MIN))      \
             ^
block/cfq-iosched.c:4760:1: note: in expansion of macro ?STORE_FUNCTION?
 STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
 ^~~~~~~~~~~~~~
block/cfq-iosched.c: In function ?cfq_low_latency_store?:
block/cfq-iosched.c:4741:13: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (__data < (MIN))      \
             ^
block/cfq-iosched.c:4765:1: note: in expansion of macro ?STORE_FUNCTION?
 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
 ^~~~~~~~~~~~~~
block/cfq-iosched.c: In function ?cfq_slice_idle_us_store?:
block/cfq-iosched.c:4775:13: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (__data < (MIN))      \
             ^
block/cfq-iosched.c:4782:1: note: in expansion of macro ?USEC_STORE_FUNCTION?
 USEC_STORE_FUNCTION(cfq_slice_idle_us_store, &cfqd->cfq_slice_idle, 0, UINT_MAX);
 ^~~~~~~~~~~~~~~~~~~
block/cfq-iosched.c: In function ?cfq_group_idle_us_store?:
block/cfq-iosched.c:4775:13: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (__data < (MIN))      \
             ^
block/cfq-iosched.c:4783:1: note: in expansion of macro ?USEC_STORE_FUNCTION?
 USEC_STORE_FUNCTION(cfq_group_idle_us_store, &cfqd->cfq_group_idle, 0, UINT_MAX);
 ^~~~~~~~~~~~~~~~~~~
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch avoids that gcc complains about fall-through when building
with W=1.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

I am currently running a large bare metal instance (i3.metal)
on EC2 with 72 cores, 512GB of RAM and NVME drives, with a
4.18 kernel. I have a workload that simulates a database
workload and I am running into lockup issues when writeback
throttling is enabled,with the hung task detector also
kicking in.

Crash dumps show that most CPUs (up to 50 of them) are
all trying to get the wbt wait queue lock while trying to add
themselves to it in __wbt_wait (see stack traces below).

[    0.948118] CPU: 45 PID: 0 Comm: swapper/45 Not tainted 4.14.51-62.38.amzn1.x86_64 #1
[    0.948119] Hardware name: Amazon EC2 i3.metal/Not Specified, BIOS 1.0 10/16/2017
[    0.948120] task: ffff883f7878c000 task.stack: ffffc9000c69c000
[    0.948124] RIP: 0010:native_queued_spin_lock_slowpath+0xf8/0x1a0
[    0.948125] RSP: 0018:ffff883f7fcc3dc8 EFLAGS: 00000046
[    0.948126] RAX: 0000000000000000 RBX: ffff887f7709ca68 RCX: ffff883f7fce2a00
[    0.948128] RDX: 000000000000001c RSI: 0000000000740001 RDI: ffff887f7709ca68
[    0.948129] RBP: 0000000000000002 R08: 0000000000b80000 R09: 0000000000000000
[    0.948130] R10: ffff883f7fcc3d78 R11: 000000000de27121 R12: 0000000000000002
[    0.948131] R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000000
[    0.948132] FS:  0000000000000000(0000) GS:ffff883f7fcc0000(0000) knlGS:0000000000000000
[    0.948134] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.948135] CR2: 000000c424c77000 CR3: 0000000002010005 CR4: 00000000003606e0
[    0.948136] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    0.948137] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    0.948138] Call Trace:
[    0.948139]  <IRQ>
[    0.948142]  do_raw_spin_lock+0xad/0xc0
[    0.948145]  _raw_spin_lock_irqsave+0x44/0x4b
[    0.948149]  ? __wake_up_common_lock+0x53/0x90
[    0.948150]  __wake_up_common_lock+0x53/0x90
[    0.948155]  wbt_done+0x7b/0xa0
[    0.948158]  blk_mq_free_request+0xb7/0x110
[    0.948161]  __blk_mq_complete_request+0xcb/0x140
[    0.948166]  nvme_process_cq+0xce/0x1a0 [nvme]
[    0.948169]  nvme_irq+0x23/0x50 [nvme]
[    0.948173]  __handle_irq_event_percpu+0x46/0x300
[    0.948176]  handle_irq_event_percpu+0x20/0x50
[    0.948179]  handle_irq_event+0x34/0x60
[    0.948181]  handle_edge_irq+0x77/0x190
[    0.948185]  handle_irq+0xaf/0x120
[    0.948188]  do_IRQ+0x53/0x110
[    0.948191]  common_interrupt+0x87/0x87
[    0.948192]  </IRQ>
....
[    0.311136] CPU: 4 PID: 9737 Comm: run_linux_amd64 Not tainted 4.14.51-62.38.amzn1.x86_64 #1
[    0.311137] Hardware name: Amazon EC2 i3.metal/Not Specified, BIOS 1.0 10/16/2017
[    0.311138] task: ffff883f6e6a8000 task.stack: ffffc9000f1ec000
[    0.311141] RIP: 0010:native_queued_spin_lock_slowpath+0xf5/0x1a0
[    0.311142] RSP: 0018:ffffc9000f1efa28 EFLAGS: 00000046
[    0.311144] RAX: 0000000000000000 RBX: ffff887f7709ca68 RCX: ffff883f7f722a00
[    0.311145] RDX: 0000000000000035 RSI: 0000000000d80001 RDI: ffff887f7709ca68
[    0.311146] RBP: 0000000000000202 R08: 0000000000140000 R09: 0000000000000000
[    0.311147] R10: ffffc9000f1ef9d8 R11: 000000001a249fa0 R12: ffff887f7709ca68
[    0.311148] R13: ffffc9000f1efad0 R14: 0000000000000000 R15: ffff887f7709ca00
[    0.311149] FS:  000000c423f30090(0000) GS:ffff883f7f700000(0000) knlGS:0000000000000000
[    0.311150] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.311151] CR2: 00007feefcea4000 CR3: 0000007f7016e001 CR4: 00000000003606e0
[    0.311152] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    0.311153] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    0.311154] Call Trace:
[    0.311157]  do_raw_spin_lock+0xad/0xc0
[    0.311160]  _raw_spin_lock_irqsave+0x44/0x4b
[    0.311162]  ? prepare_to_wait_exclusive+0x28/0xb0
[    0.311164]  prepare_to_wait_exclusive+0x28/0xb0
[    0.311167]  wbt_wait+0x127/0x330
[    0.311169]  ? finish_wait+0x80/0x80
[    0.311172]  ? generic_make_request+0xda/0x3b0
[    0.311174]  blk_mq_make_request+0xd6/0x7b0
[    0.311176]  ? blk_queue_enter+0x24/0x260
[    0.311178]  ? generic_make_request+0xda/0x3b0
[    0.311181]  generic_make_request+0x10c/0x3b0
[    0.311183]  ? submit_bio+0x5c/0x110
[    0.311185]  submit_bio+0x5c/0x110
[    0.311197]  ? __ext4_journal_stop+0x36/0xa0 [ext4]
[    0.311210]  ext4_io_submit+0x48/0x60 [ext4]
[    0.311222]  ext4_writepages+0x810/0x11f0 [ext4]
[    0.311229]  ? do_writepages+0x3c/0xd0
[    0.311239]  ? ext4_mark_inode_dirty+0x260/0x260 [ext4]
[    0.311240]  do_writepages+0x3c/0xd0
[    0.311243]  ? _raw_spin_unlock+0x24/0x30
[    0.311245]  ? wbc_attach_and_unlock_inode+0x165/0x280
[    0.311248]  ? __filemap_fdatawrite_range+0xa3/0xe0
[    0.311250]  __filemap_fdatawrite_range+0xa3/0xe0
[    0.311253]  file_write_and_wait_range+0x34/0x90
[    0.311264]  ext4_sync_file+0x151/0x500 [ext4]
[    0.311267]  do_fsync+0x38/0x60
[    0.311270]  SyS_fsync+0xc/0x10
[    0.311272]  do_syscall_64+0x6f/0x170
[    0.311274]  entry_SYSCALL_64_after_hwframe+0x42/0xb7

In the original patch, wbt_done is waking up all the exclusive
processes in the wait queue, which can cause a thundering herd
if there is a large number of writer threads in the queue. The
original intention of the code seems to be to wake up one thread
only however, it uses wake_up_all() in __wbt_done(), and then
uses the following check in __wbt_wait to have only one thread
actually get out of the wait loop:

if (waitqueue_active(&rqw->wait) &&
            rqw->wait.head.next != &wait->entry)
                return false;

The problem with this is that the wait entry in wbt_wait is
define with DEFINE_WAIT, which uses the autoremove wakeup function.
That means that the above check is invalid - the wait entry will
have been removed from the queue already by the time we hit the
check in the loop.

Secondly, auto-removing the wait entries also means that the wait
queue essentially gets reordered "randomly" (e.g. threads re-add
themselves in the order they got to run after being woken up).
Additionally, new requests entering wbt_wait might overtake requests
that were queued earlier, because the wait queue will be
(temporarily) empty after the wake_up_all, so the waitqueue_active
check will not stop them. This can cause certain threads to starve
under high load.

The fix is to leave the woken up requests in the queue and remove
them in finish_wait() once the current thread breaks out of the
wait loop in __wbt_wait. This will ensure new requests always
end up at the back of the queue, and they won't overtake requests
that are already in the wait queue. With that change, the loop
in wbt_wait is also in line with many other wait loops in the kernel.
Waking up just one thread drastically reduces lock contention, as
does moving the wait queue add/remove out of the loop.

A significant drop in lockdep's lock contention numbers is seen when
running the test application on the patched kernel.
Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The target loopback driver is a low-level driver for the SCSI subsystem,
and as such needs to depend on it.

Fixes: 8a39a047 ("target: don't depend on SCSI")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

When the initial discovery fails the subsystem hasn't been setup yet
in nvme_mpath_stop, and we can't dereference ctrl->subsys.

Fixes: 0d0b660f ("nvme: add ANA support")
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Return statements in functions returning bool should use true or false
instead of an integer value.

This code was detected with the help of Coccinelle.
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

A minor version number increase should not break backwards
compatibility.

Fixes: 3cb98f84 ("lightnvm: add minor version to generic geometry")
Reviewed-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull NVMe changes from Christoph:

"This contains the support for TP4004, Asymmetric Namespace Access,
 which makes NVMe multipathing usable in practice."

* 'nvme-4.19' of git://git.infradead.org/nvme:
  nvmet: use Retain Async Event bit to clear AEN
  nvmet: support configuring ANA groups
  nvmet: add minimal ANA support
  nvmet: track and limit the number of namespaces per subsystem
  nvmet: keep a port pointer in nvmet_ctrl
  nvme: add ANA support
  nvme: remove nvme_req_needs_failover
  nvme: simplify the API for getting log pages
  nvme.h: add ANA definitions
  nvme.h: add support for the log specific field
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull in 4.18-rc6 to get the NVMe core AEN change to avoid a
merge conflict down the line.
Signed-of-by: Jens Axboe <axboe@kernel.dk>

To avoid introducing problems like those fixed in commit f7068114
("sr: pass down correctly sized SCSI sense buffer"), this creates a macro
wrapper for scsi_execute() that verifies the size of the sense buffer
similar to what was done for command string sizes in commit 3756f640
("exec: avoid gcc-8 warning for get_task_comm").

Another solution could be to add a length argument to scsi_execute(),
but this function already takes a lot of arguments and Jens was not fond
of that approach.

Additionally, this moves the SCSI_SENSE_BUFFERSIZE definition into
scsi_device.h, and removes a redundant include for scsi_device.h from
scsi_cmnd.h.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

To support future compile-time sizeof() checks that will be able to
validate the length of sense buffers, this removes the only dynamically
allocated sense buffers in the tree by putting the 96 byte sense buffers
on the stack.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This removes more casts of struct request_sense and uses the standard
struct scsi_sense_hdr instead. This also fixes any possible stale values
since the prior code did not check the sense length.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This is already able to process the sense buffer, so remove the redundant
parsing during the failure path. This also fixes any possible stale values
since the prior code did not check the sense length.
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

There is a lot of needless struct request_sense usage in the CDROM
code. These can all be struct scsi_sense_hdr instead, to avoid any
confusion over their respective structure sizes. This patch is a lot
of noise changing "sense" to "sshdr", but the final code is more
readable to distinguish between "sense" meaning "struct request_sense"
and "sshdr" meaning "struct scsi_sense_hdr".
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>