Define REQ_OP_ZONE_APPEND to append-write sectors to a zone of a zoned
block device. This is a no-merge write operation.

A zone append write BIO must:
* Target a zoned block device
* Have a sector position indicating the start sector of the target zone
* The target zone must be a sequential write zone
* The BIO must not cross a zone boundary
* The BIO size must not be split to ensure that a single range of LBAs
  is written with a single command.

Implement these checks in generic_make_request_checks() using the
helper function blk_check_zone_append(). To avoid write append BIO
splitting, introduce the new max_zone_append_sectors queue limit
attribute and ensure that a BIO size is always lower than this limit.
Export this new limit through sysfs and check these limits in bio_full().

Also when a LLDD can't dispatch a request to a specific zone, it
will return BLK_STS_ZONE_RESOURCE indicating this request needs to
be delayed, e.g.  because the zone it will be dispatched to is still
write-locked. If this happens set the request aside in a local list
to continue trying dispatching requests such as READ requests or a
WRITE/ZONE_APPEND requests targetting other zones. This way we can
still keep a high queue depth without starving other requests even if
one request can't be served due to zone write-locking.

Finally, make sure that the bio sector position indicates the actual
write position as indicated by the device on completion.
Signed-off-by: NKeith Busch <kbusch@kernel.org>
[ jth: added zone-append specific add_page and merge_page helpers ]
Signed-off-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Rename __bio_add_pc_page() to bio_add_hw_page() and explicitly pass in a
max_sectors argument.

This max_sectors argument can be used to specify constraints from the
hardware.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
[ jth: rebased and made public for blk-map.c ]
Signed-off-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NDaniel Wagner <dwagner@suse.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

blk_queue_zone_is_seq() and blk_queue_zone_no() have not been called with
CONFIG_BLK_DEV_ZONED disabled until now.

The introduction of REQ_OP_ZONE_APPEND will change this, so we need to
provide noop fallbacks for the !CONFIG_BLK_DEV_ZONED case.
Signed-off-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Sync dio could be big, or may take long time in discard or in case of
IO failure.

We have prevented task hung in submit_bio_wait() and blk_execute_rq(),
so apply the same trick for prevent task hung from happening in sync dio.

Add helper of blk_io_schedule() and use io_schedule_timeout() to prevent
task hung warning.
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Cc: Salman Qazi <sqazi@google.com>
Cc: Jesse Barnes <jsbarnes@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

gendisk can't be gone when there is IO activity, so not hold
part0's refcount in IO path.
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@infradead.org>
Cc: Yufen Yu <yuyufen@huawei.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hou Tao <houtao1@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Put all fields accessed in IO path together at the beginning
of the struct, so that all can be fetched in single cacheline.
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@infradead.org>
Cc: Yufen Yu <yuyufen@huawei.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hou Tao <houtao1@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The seqcount of 'nr_sects_seq' is only needed in case of 32bit SMP,
so define it just for 32bit SMP.
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@infradead.org>
Cc: Yufen Yu <yuyufen@huawei.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hou Tao <houtao1@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

delete_partition() clears the cached last_lookup partition. However the
.last_lookup cache may be overwritten by one IO path after it is cleared
from delete_partition(). Then another IO path may use the cached deleting
partition after hd_struct_free() is called, then use-after-free is triggered
on the cached partition.

Fixes the issue by the following approach:

1) always get the partition's refcount via hd_struct_try_get() before
setting .last_lookup

2) move clearing .last_lookup from delete_partition() to hd_struct_free()
which is the release handle of the partition's percpu-refcount, so that no
IO path can cache deleteing partition via .last_lookup.

It is one candidate approach of Yufen's patch[1] which adds overhead
in fast path by indirect lookup which may introduce one extra cacheline
in IO path. Also this patch relies on percpu-refcount's protection, and
it is easier to understand and verify.

[1] https://lore.kernel.org/linux-block/20200109013551.GB9655@ming.t460p/T/#tReported-by: NYufen Yu <yuyufen@huawei.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hou Tao <houtao1@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When we increase hardware queue count, blk_mq_update_queue_map will
reset the mapping between cpu and hardware queue base on the hardware
queue count(set->nr_hw_queues). The mapping cannot be reset if it
encounters error in blk_mq_realloc_hw_ctxs, but the fallback flow will
continue using it, then blk_mq_map_swqueue will touch a invalid memory,
because the mapping points to a wrong hctx.

blktest block/030:

null_blk: module loaded
Increasing nr_hw_queues to 8 fails, fallback to 1
==================================================================
BUG: KASAN: null-ptr-deref in blk_mq_map_swqueue+0x2f2/0x830
Read of size 8 at addr 0000000000000128 by task nproc/8541

CPU: 5 PID: 8541 Comm: nproc Not tainted 5.7.0-rc4-dbg+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
Call Trace:
dump_stack+0xa5/0xe6
__kasan_report.cold+0x65/0xbb
kasan_report+0x45/0x60
check_memory_region+0x15e/0x1c0
__kasan_check_read+0x15/0x20
blk_mq_map_swqueue+0x2f2/0x830
__blk_mq_update_nr_hw_queues+0x3df/0x690
blk_mq_update_nr_hw_queues+0x32/0x50
nullb_device_submit_queues_store+0xde/0x160 [null_blk]
configfs_write_file+0x1c4/0x250 [configfs]
__vfs_write+0x4c/0x90
vfs_write+0x14b/0x2d0
ksys_write+0xdd/0x180
__x64_sys_write+0x47/0x50
do_syscall_64+0x6f/0x310
entry_SYSCALL_64_after_hwframe+0x49/0xb3
Signed-off-by: NWeiping Zhang <zhangweiping@didiglobal.com>
Tested-by: NBart van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Fixes: 1cd925d5 ("bdi: remove the name field in struct backing_dev_info")
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Instead just call the CDROM layer functionality directly.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The name is only printed for a not registered bdi in writeback.  Use the
device name there as is more useful anyway for the unlike case that the
warning triggers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Merge the _node vs normal version and drop the superflous gfp_t argument.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Split out a new bdi_set_owner helper to set the owner, and move the policy
for creating the bdi name back into genhd.c, where it belongs.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

bdi_register_va is only used by super.c, which can't be modular.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

All external users of device_create_vargs are gone, so remove it and
open code it in the only caller.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

rename blk_mq_alloc_rq_maps to blk_mq_alloc_map_and_requests,
this function allocs both map and request, make function name align
with funtion.
Signed-off-by: NWeiping Zhang <zhangweiping@didiglobal.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

rename __blk_mq_alloc_rq_map to __blk_mq_alloc_map_and_request,
actually it alloc both map and request, make function name
align with function.
Signed-off-by: NWeiping Zhang <zhangweiping@didiglobal.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Alloc new map and request for new hardware queue when increse
hardware queue count. Before this patch, it will show a
warning for each new hardware queue, but it's not enough, these
hctx have no maps and reqeust, when a bio was mapped to these
hardware queue, it will trigger kernel panic when get request
from these hctx.

Test environment:
 * A NVMe disk supports 128 io queues
 * 96 cpus in system

A corner case can always trigger this panic, there are 96
io queues allocated for HCTX_TYPE_DEFAULT type, the corresponding kernel
log: nvme nvme0: 96/0/0 default/read/poll queues. Now we set nvme write
queues to 96, then nvme will alloc others(32) queues for read, but
blk_mq_update_nr_hw_queues does not alloc map and request for these new
added io queues. So when process read nvme disk, it will trigger kernel
panic when get request from these hardware context.

Reproduce script:

nr=$(expr `cat /sys/block/nvme0n1/device/queue_count` - 1)
echo $nr > /sys/module/nvme/parameters/write_queues
echo 1 > /sys/block/nvme0n1/device/reset_controller
dd if=/dev/nvme0n1 of=/dev/null bs=4K count=1

[ 8040.805626] ------------[ cut here ]------------
[ 8040.805627] WARNING: CPU: 82 PID: 12921 at block/blk-mq.c:2578 blk_mq_map_swqueue+0x2b6/0x2c0
[ 8040.805627] Modules linked in: nvme nvme_core nf_conntrack_netlink xt_addrtype br_netfilter overlay xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nft_counter nf_nat_tftp nf_conntrack_tftp nft_masq nf_tables_set nft_fib_inet nft_f
ib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack tun bridge nf_defrag_ipv6 nf_defrag_ipv4 stp llc ip6_tables ip_tables nft_compat rfkill ip_set nf_tables nfne
tlink sunrpc intel_rapl_msr intel_rapl_common skx_edac nfit libnvdimm x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass ipmi_ssif crct10dif_pclmul crc32_pclmul iTCO_wdt iTCO_vendor_support ghash_clmulni_intel intel_
cstate intel_uncore raid0 joydev intel_rapl_perf ipmi_si pcspkr mei_me ioatdma sg ipmi_devintf mei i2c_i801 dca lpc_ich ipmi_msghandler acpi_power_meter acpi_pad xfs libcrc32c sd_mod ast i2c_algo_bit drm_vram_helper drm_ttm_helper ttm d
rm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops
[ 8040.805637]  ahci drm i40e libahci crc32c_intel libata t10_pi wmi dm_mirror dm_region_hash dm_log dm_mod [last unloaded: nvme_core]
[ 8040.805640] CPU: 82 PID: 12921 Comm: kworker/u194:2 Kdump: loaded Tainted: G        W         5.6.0-rc5.78317c+ #2
[ 8040.805640] Hardware name: Inspur SA5212M5/YZMB-00882-104, BIOS 4.0.9 08/27/2019
[ 8040.805641] Workqueue: nvme-reset-wq nvme_reset_work [nvme]
[ 8040.805642] RIP: 0010:blk_mq_map_swqueue+0x2b6/0x2c0
[ 8040.805643] Code: 00 00 00 00 00 41 83 c5 01 44 39 6d 50 77 b8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b bb 98 00 00 00 89 d6 e8 8c 81 03 00 eb 83 <0f> 0b e9 52 ff ff ff 0f 1f 00 0f 1f 44 00 00 41 57 48 89 f1 41 56
[ 8040.805643] RSP: 0018:ffffba590d2e7d48 EFLAGS: 00010246
[ 8040.805643] RAX: 0000000000000000 RBX: ffff9f013e1ba800 RCX: 000000000000003d
[ 8040.805644] RDX: ffff9f00ffff6000 RSI: 0000000000000003 RDI: ffff9ed200246d90
[ 8040.805644] RBP: ffff9f00f6a79860 R08: 0000000000000000 R09: 000000000000003d
[ 8040.805645] R10: 0000000000000001 R11: ffff9f0138c3d000 R12: ffff9f00fb3a9008
[ 8040.805645] R13: 000000000000007f R14: ffffffff96822660 R15: 000000000000005f
[ 8040.805645] FS:  0000000000000000(0000) GS:ffff9f013fa80000(0000) knlGS:0000000000000000
[ 8040.805646] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 8040.805646] CR2: 00007f7f397fa6f8 CR3: 0000003d8240a002 CR4: 00000000007606e0
[ 8040.805647] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 8040.805647] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 8040.805647] PKRU: 55555554
[ 8040.805647] Call Trace:
[ 8040.805649]  blk_mq_update_nr_hw_queues+0x31b/0x390
[ 8040.805650]  nvme_reset_work+0xb4b/0xeab [nvme]
[ 8040.805651]  process_one_work+0x1a7/0x370
[ 8040.805652]  worker_thread+0x1c9/0x380
[ 8040.805653]  ? max_active_store+0x80/0x80
[ 8040.805655]  kthread+0x112/0x130
[ 8040.805656]  ? __kthread_parkme+0x70/0x70
[ 8040.805657]  ret_from_fork+0x35/0x40
[ 8040.805658] ---[ end trace b5f13b1e73ccb5d3 ]---
[ 8229.365135] BUG: kernel NULL pointer dereference, address: 0000000000000004
[ 8229.365165] #PF: supervisor read access in kernel mode
[ 8229.365178] #PF: error_code(0x0000) - not-present page
[ 8229.365191] PGD 0 P4D 0
[ 8229.365201] Oops: 0000 [#1] SMP PTI
[ 8229.365212] CPU: 77 PID: 13024 Comm: dd Kdump: loaded Tainted: G        W         5.6.0-rc5.78317c+ #2
[ 8229.365232] Hardware name: Inspur SA5212M5/YZMB-00882-104, BIOS 4.0.9 08/27/2019
[ 8229.365253] RIP: 0010:blk_mq_get_tag+0x227/0x250
[ 8229.365265] Code: 44 24 04 44 01 e0 48 8b 74 24 38 65 48 33 34 25 28 00 00 00 75 33 48 83 c4 40 5b 5d 41 5c 41 5d 41 5e c3 48 8d 68 10 4c 89 ef <44> 8b 60 04 48 89 ee e8 dd f9 ff ff 83 f8 ff 75 c8 e9 67 fe ff ff
[ 8229.365304] RSP: 0018:ffffba590e977970 EFLAGS: 00010246
[ 8229.365317] RAX: 0000000000000000 RBX: ffff9f00f6a79860 RCX: ffffba590e977998
[ 8229.365333] RDX: 0000000000000000 RSI: ffff9f012039b140 RDI: ffffba590e977a38
[ 8229.365349] RBP: 0000000000000010 R08: ffffda58ff94e190 R09: ffffda58ff94e198
[ 8229.365365] R10: 0000000000000011 R11: ffff9f00f6a79860 R12: 0000000000000000
[ 8229.365381] R13: ffffba590e977a38 R14: ffff9f012039b140 R15: 0000000000000001
[ 8229.365397] FS:  00007f481c230580(0000) GS:ffff9f013f940000(0000) knlGS:0000000000000000
[ 8229.365415] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 8229.365428] CR2: 0000000000000004 CR3: 0000005f35e26004 CR4: 00000000007606e0
[ 8229.365444] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 8229.365460] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 8229.365476] PKRU: 55555554
[ 8229.365484] Call Trace:
[ 8229.365498]  ? finish_wait+0x80/0x80
[ 8229.365512]  blk_mq_get_request+0xcb/0x3f0
[ 8229.365525]  blk_mq_make_request+0x143/0x5d0
[ 8229.365538]  generic_make_request+0xcf/0x310
[ 8229.365553]  ? scan_shadow_nodes+0x30/0x30
[ 8229.365564]  submit_bio+0x3c/0x150
[ 8229.365576]  mpage_readpages+0x163/0x1a0
[ 8229.365588]  ? blkdev_direct_IO+0x490/0x490
[ 8229.365601]  read_pages+0x6b/0x190
[ 8229.365612]  __do_page_cache_readahead+0x1c1/0x1e0
[ 8229.365626]  ondemand_readahead+0x182/0x2f0
[ 8229.365639]  generic_file_buffered_read+0x590/0xab0
[ 8229.365655]  new_sync_read+0x12a/0x1c0
[ 8229.365666]  vfs_read+0x8a/0x140
[ 8229.365676]  ksys_read+0x59/0xd0
[ 8229.365688]  do_syscall_64+0x55/0x1d0
[ 8229.365700]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NWeiping Zhang <zhangweiping@didiglobal.com>
Tested-by: NWeiping Zhang <zhangweiping@didiglobal.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

blk_mq_realloc_tag_set_tags will update set->nr_hw_queues, so
save old set->nr_hw_queues before call this function.
Signed-off-by: NWeiping Zhang <zhangweiping@didiglobal.com>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Allocation:

__blk_mq_alloc_rq_map
	blk_mq_alloc_rq_map
		blk_mq_alloc_rq_map
			tags = blk_mq_init_tags : kzalloc_node:
			tags->rqs = kcalloc_node
			tags->static_rqs = kcalloc_node
	blk_mq_alloc_rqs
		p = alloc_pages_node
		tags->static_rqs[i] = p + offset;

Free:

blk_mq_free_rq_map
	kfree(tags->rqs);
	kfree(tags->static_rqs);
	blk_mq_free_tags
		kfree(tags);

The page allocated in blk_mq_alloc_rqs cannot be released,
so we should use blk_mq_free_map_and_requests here.

blk_mq_free_map_and_requests
	blk_mq_free_rqs
		__free_pages : cleanup for blk_mq_alloc_rqs
	blk_mq_free_rq_map : cleanup for blk_mq_alloc_rq_map
Signed-off-by: NWeiping Zhang <zhangweiping@didiglobal.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Pull in block-5.7 fixes for 5.8. Mostly to resolve a conflict with
the blk-iocost changes, but we also need the base of the bdi
use-after-free as well as we build on top of it.

* block-5.7:
  nvme: fix possible hang when ns scanning fails during error recovery
  nvme-pci: fix "slimmer CQ head update"
  bdi: add a ->dev_name field to struct backing_dev_info
  bdi: use bdi_dev_name() to get device name
  bdi: move bdi_dev_name out of line
  vboxsf: don't use the source name in the bdi name
  iocost: protect iocg->abs_vdebt with iocg->waitq.lock
  block: remove the bd_openers checks in blk_drop_partitions
  nvme: prevent double free in nvme_alloc_ns() error handling
  null_blk: Cleanup zoned device initialization
  null_blk: Fix zoned command handling
  block: remove unused header
  blk-iocost: Fix error on iocost_ioc_vrate_adj
  bdev: Reduce time holding bd_mutex in sync in blkdev_close()
  buffer: remove useless comment and WB_REASON_FREE_MORE_MEM, reason.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When the controller is reconnecting, the host fails I/O and admin
commands as the host cannot reach the controller. ns scanning may
revalidate namespaces during that period and it is wrong to remove
namespaces due to these failures as we may hang (see 205da243).

One command that may fail is nvme_identify_ns_descs. Since we return
success due to having ns identify descriptor list optional, we continue
to compare ns identifiers in nvme_revalidate_disk, obviously fail and
return -ENODEV to nvme_validate_ns, which will remove the namespace.

Exactly what we don't want to happen.

Fixes: 22802bf7 ("nvme: Namepace identification descriptor list is optional")
Tested-by: NAnton Eidelman <anton@lightbitslabs.com>
Signed-off-by: NSagi Grimberg <sagi@grimberg.me>
Reviewed-by: NKeith Busch <kbusch@kernel.org>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Pre-incrementing ->cq_head can't be done in memory because OOB value
can be observed by another context.

This devalues space savings compared to original code :-\

	$ ./scripts/bloat-o-meter ../vmlinux-000 ../obj/vmlinux
	add/remove: 0/0 grow/shrink: 0/4 up/down: 0/-32 (-32)
	Function                                     old     new   delta
	nvme_poll_irqdisable                         464     456      -8
	nvme_poll                                    455     447      -8
	nvme_irq                                     388     380      -8
	nvme_dev_disable                             955     947      -8

But the code is minimal now: one read for head, one read for q_depth,
one increment, one comparison, single instruction phase bit update and
one write for new head.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Reported-by: NJohn Garry <john.garry@huawei.com>
Tested-by: NJohn Garry <john.garry@huawei.com>
Fixes: e2a366a4 ("nvme-pci: slimmer CQ head update")
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Cache a copy of the name for the life time of the backing_dev_info
structure so that we can reference it even after unregistering.

Fixes: 68f23b89 ("memcg: fix a crash in wb_workfn when a device disappears")
Reported-by: NYufen Yu <yuyufen@huawei.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Use the common interface bdi_dev_name() to get device name.
Signed-off-by: NYufen Yu <yuyufen@huawei.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>

Add missing <linux/backing-dev.h> include BFQ
Signed-off-by: NJens Axboe <axboe@kernel.dk>

bdi_dev_name is not a fast path function, move it out of line.  This
prepares for using it from modular callers without having to export
an implementation detail like bdi_unknown_name.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Simplify the bdi name to mirror what we are doing elsewhere, and
drop them name in favor of just using a number.  This avoids a
potentially very long bdi name.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

abs_vdebt is an atomic_64 which tracks how much over budget a given cgroup
is and controls the activation of use_delay mechanism. Once a cgroup goes
over budget from forced IOs, it has to pay it back with its future budget.
The progress guarantee on debt paying comes from the iocg being active -
active iocgs are processed by the periodic timer, which ensures that as time
passes the debts dissipate and the iocg returns to normal operation.

However, both iocg activation and vdebt handling are asynchronous and a
sequence like the following may happen.

1. The iocg is in the process of being deactivated by the periodic timer.

2. A bio enters ioc_rqos_throttle(), calls iocg_activate() which returns
   without anything because it still sees that the iocg is already active.

3. The iocg is deactivated.

4. The bio from #2 is over budget but needs to be forced. It increases
   abs_vdebt and goes over the threshold and enables use_delay.

5. IO control is enabled for the iocg's subtree and now IOs are attributed
   to the descendant cgroups and the iocg itself no longer issues IOs.

This leaves the iocg with stuck abs_vdebt - it has debt but inactive and no
further IOs which can activate it. This can end up unduly punishing all the
descendants cgroups.

The usual throttling path has the same issue - the iocg must be active while
throttled to ensure that future event will wake it up - and solves the
problem by synchronizing the throttling path with a spinlock. abs_vdebt
handling is another form of overage handling and shares a lot of
characteristics including the fact that it isn't in the hottest path.

This patch fixes the above and other possible races by strictly
synchronizing abs_vdebt and use_delay handling with iocg->waitq.lock.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NVlad Dmitriev <vvd@fb.com>
Cc: stable@vger.kernel.org # v5.4+
Fixes: e1518f63 ("blk-iocost: Don't let merges push vtime into the future")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Instead just call the CDROM layer functionality directly.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Instead just call the CDROM layer functionality directly, and turn the
hot mess in isofs_get_last_session into remotely readable code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Instead just call the CDROM layer functionality directly.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Factor out a version of the CDROMMULTISESSION ioctl handler that can
be called directly from kernel space.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Factor out a version of the CDROMREADTOCENTRY ioctl handler that can
be called directly from kernel space.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Give the cdrom_read_tocentry function and ide_ prefix to not conflict
with the soon to be added generic function.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Add a pointer to the CDROM information structure to struct gendisk.
This will allow various removable media file systems to call directly
into the CDROM layer instead of abusing ioctls with kernel pointers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Wrapping numbers in strings is used by some to work around bit-width issues in
some enviroments. The problem isn't innate to json and the workaround seems to
cause more integration problems than help. Let's drop the string wrapping.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This is to help external tools to decide whether iocost_monitor has all its
requirements met or not based on the exit status of an -i0 run.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

On each IO completion, iocost decides whether the IO met or missed its latency
target. Currently, the targets are fixed numbers per IO type. While this can be
good enough for loose latency targets way higher than typical completion
latencies, the effect of IO size makes it difficult to tighten the latency
target - a target adequate for 4k IOs might be too tight for 512k IOs and
vice-versa.

iocost already has all the necessary information to account for different IO
sizes when testing whether the latency target is met as iocost can calculate the
size vtime cost of a given IO. This patch updates the completion path to
calculate the size vtime cost of the IO, deduct the nsec equivalent from the
observed latency and use the adjusted value to decide whether the target is met.

This makes latency targets independent from IO size and enables determining
adequate latency targets with fixed size fio runs.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Andy Newell <newella@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The use_delay mechanism was introduced by blk-iolatency to hold memory
allocators accountable for the reclaim and other shared IOs they cause. The
duration of the delay is dynamically balanced between iolatency increasing the
value on each target miss and it auto-decaying as time passes and threads get
delayed on it.

While this works well for iolatency, iocost's control model isn't compatible
with it. There is no repeated "violation" events which can be balanced against
auto-decaying. iocost instead knows how much a given cgroup is over budget and
wants to prevent that cgroup from issuing IOs while over budget. Until now,
iocost has been adding the cost of force-issued IOs. However, this doesn't
reflect the amount which is already over budget and is simply not enough to
counter the auto-decaying allowing anon-memory leaking low priority cgroup to
go over its alloted share of IOs.

As auto-decaying doesn't make much sense for iocost, this patch introduces a
different mode of operation for use_delay - when blkcg_set_delay() are used
insted of blkcg_add/use_delay(), the delay duration is not auto-decayed until it
is explicitly cleared with blkcg_clear_delay(). iocost is updated to keep the
delay duration synchronized to the budget overage amount.

With this change, iocost can effectively police cgroups which generate
significant amount of force-issued IOs.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>