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2019-12-20sbitmap: only queue kyber's wait callback if not already activeDavid Jeffery1-1/+1
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: Omar Sandoval <osandov@fb.com> Signed-off-by: David Jeffery <djeffery@redhat.com> Reported-by: John Pittman <jpittman@redhat.com> Tested-by: John Pittman <jpittman@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-13sbitmap: Delete sbitmap_any_bit_clear()John Garry1-17/+0
Since the only caller of this function has been deleted, delete this one also. Signed-off-by: John Garry <john.garry@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-01sbitmap: Replace cmpxchg with xchgPavel Begunkov1-7/+3
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: Omar Sandoval <osandov@fb.com> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-06-05treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 328Thomas Gleixner1-12/+1
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: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexios Zavras <alexios.zavras@intel.com> Reviewed-by: Armijn Hemel <armijn@tjaldur.nl> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190530000435.923873561@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-23sbitmap: fix improper use of smp_mb__before_atomic()Andrea Parri1-1/+1
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: 6c0ca7ae292ad ("sbitmap: fix wakeup hang after sbq resize") Cc: stable@vger.kernel.org Reported-by: "Paul E. McKenney" <paulmck@linux.ibm.com> Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Reviewed-by: Ming 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: Jens Axboe <axboe@kernel.dk>
2019-03-25sbitmap: order READ/WRITE freed instance and setting clear bitMing Lei1-0/+11
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: ea86ea2cdced20057da ("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: Omar Sandoval <osandov@fb.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-01-15sbitmap: Protect swap_lock from hardirqMing Lei1-2/+3
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: Ming Lei <ming.lei@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-15sbitmap: Protect swap_lock from softirqsSteven Rostedt (VMware)1-10/+2
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: Clark Williams <williams@redhat.com> Fixes: 58ab5e32e6fd ("sbitmap: silence bogus lockdep IRQ warning") Fixes: ea86ea2cdced ("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: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-12-20sbitmap: add helpers for add/del wait queue handlingJens Axboe1-4/+26
After commit 5d2ee7122c73, 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: Ming Lei <ming.lei@redhat.com> Reviewed-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-11sbitmap: flush deferred clears for resize and shallow getsJens Axboe1-43/+51
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: Bart Van Assche <bvanassche@acm.org> Tested-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-12-09sbitmap: silence bogus lockdep IRQ warningJens Axboe1-0/+8
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_5d2ee7122c73_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: Ming Lei <ming.lei@redhat.com> Tested-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-30sbitmap: optimize wakeup checkJens Axboe1-0/+28
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: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-30sbitmap: ammortize cost of clearing bitsJens Axboe1-8/+73
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: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-11-29sbitmap: don't loop for find_next_zero_bit() for !round_robinJens Axboe1-8/+13
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: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-06-12treewide: kzalloc_node() -> kcalloc_node()Kees Cook1-1/+1
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: Kees Cook <keescook@chromium.org>
2018-05-24blk-mq: avoid starving tag allocation after allocating process migratesMing Lei1-14/+15
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: Omar Sandoval <osandov@fb.com> Signed-off-by: Ming 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: Jens Axboe <axboe@kernel.dk>
2018-05-14sbitmap: fix race in wait batch accountingJens Axboe1-10/+25
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: 6c0ca7ae292a ("sbitmap: fix wakeup hang after sbq resize") Reviewed-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-05-10sbitmap: warn if using smaller shallow depth than was setupOmar Sandoval1-0/+2
Make sure the user passed the right value to sbitmap_queue_min_shallow_depth(). Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-05-10sbitmap: fix missed wakeups caused by sbitmap_queue_get_shallow()Omar Sandoval1-9/+40
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: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-02-28sbitmap: use test_and_set_bit_lock()/clear_bit_unlock()Omar Sandoval1-5/+5
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: Tejun Heo <tj@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-12-22blk-mq: improve heavily contended tag caseJens Axboe1-1/+1
Even with a number of waitqueues, we can get into a situation where we are heavily contended on the waitqueue lock. I got a report on spc1 where we're spending seconds doing this. Arguably the use case is nasty, I reproduce it with one device and 1000 threads banging on the device. But that doesn't mean we shouldn't be handling it better. What ends up happening is that a thread will fail to get a tag, add itself to the waitqueue, and subsequently get woken up when a tag is freed - only to find itself going back to sleep on the waitqueue. Instead of waking all threads, use an exclusive wait and wake up our sbitmap batch count instead. This seems to work well for me (massive improvement for this use case), and it survives basic testing. But I haven't fully verified it yet. An additional improvement is running the queue and checking for a new tag BEFORE needing to add ourselves to the waitqueue. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-04-14sbitmap: add sbitmap_get_shallow() operationOmar Sandoval1-7/+68
This operation supports the use case of limiting the number of bits that can be allocated for a given operation. Rather than setting aside some bits at the end of the bitmap, we can set aside bits in each word of the bitmap. This means we can keep the allocation hints spread out and support sbitmap_resize() nicely at the cost of lower granularity for the allowed depth. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-03-02kasan, sched/headers: Uninline kasan_enable/disable_current()Ingo Molnar1-0/+1
<linux/kasan.h> is a low level header that is included early in affected kernel headers. But it includes <linux/sched.h> which complicates the cleanup of sched.h dependencies. But kasan.h has almost no need for sched.h: its only use of scheduler functionality is in two inline functions which are not used very frequently - so uninline kasan_enable_current() and kasan_disable_current(). Also add a <linux/sched.h> dependency to a .c file that depended on kasan.h including it. This paves the way to remove the <linux/sched.h> include from kasan.h. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-01-27sbitmap: add helpers for dumping to a seq_fileOmar Sandoval1-0/+91
This is useful debugging information that will be used in the blk-mq debugfs directory. Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Omar Sandoval <osandov@fb.com> Changed 'weight' to 'busy'. Signed-off-by: Jens Axboe <axboe@fb.com>
2017-01-18sbitmap: fix wakeup hang after sbq resizeOmar Sandoval1-5/+30
When we resize a struct sbitmap_queue, we update the wakeup batch size, but we don't update the wait count in the struct sbq_wait_states. If we resized down from a size which could use a bigger batch size, these counts could be too large and cause us to miss necessary wakeups. To fix this, update the wait counts when we resize (ensuring some careful memory ordering so that it's safe w.r.t. concurrent clears). This also fixes a theoretical issue where two threads could end up bumping the wait count up by the batch size, which could also potentially lead to hangs. Reported-by: Martin Raiber <martin@urbackup.org> Fixes: e3a2b3f931f5 ("blk-mq: allow changing of queue depth through sysfs") Fixes: 2971c35f3588 ("blk-mq: bitmap tag: fix race on blk_mq_bitmap_tags::wake_cnt") Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-01-18sbitmap: use smp_mb__after_atomic() in sbq_wake_up()Omar Sandoval1-3/+10
We always do an atomic clear_bit() right before we call sbq_wake_up(), so we can use smp_mb__after_atomic(). While we're here, comment the memory barriers in here a little more. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-19sbitmap: initialize weight to zeroColin Ian King1-1/+1
Variable weight is not being initialized to zero before it is used to compute the weight sum. Ensure it is initialized to zero. Found with static analysis with cppcheck: [lib/sbitmap.c:177]: (error) Uninitialized variable: weight Signed-off-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17sbitmap: don't update the allocation hint on clear after resizeOmar Sandoval1-1/+1
If we have a bunch of high-numbered bits allocated and then we resize the struct sbitmap_queue, when those bits get cleared, we'll update the hint and then have to re-randomize it repeatedly. Avoid that by checking that the cleared bit is still a valid hint. No measurable performance difference in the common case. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17sbitmap: re-initialize allocation hints after resizeOmar Sandoval1-2/+7
After a struct sbitmap_queue is resized smaller, the allocation hints may still be set to bits beyond the new depth of the bitmap. This means that, for example, if the number of blk-mq tags is reduced through sysfs, more requests than the nominal queue depth may be in flight. It's tempting to fix this at resize time by doing a one-time reinitialization of the hints, but this can race with __sbitmap_queue_get() updating the hint. Instead, check the hint before we use it. This caused no measurable performance difference in my synthetic benchmarks. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17sbitmap: randomize initial alloc_hint valuesOmar Sandoval1-0/+6
In order to get good cache behavior from a sbitmap, we want each CPU to stick to its own cacheline(s) as much as possible. This might happen naturally as the bitmap gets filled up and the alloc_hint values spread out, but we really want this behavior from the start. blk-mq apparently intended to do this, but the code to do this was never wired up. Get rid of the dead code and make it part of the sbitmap library. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17sbitmap: push alloc policy into sbitmap_queueOmar Sandoval1-6/+8
Again, there's no point in passing this in every time. Make it part of struct sbitmap_queue and clean up the API. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17sbitmap: push per-cpu last_tag into sbitmap_queueOmar Sandoval1-1/+34
Allocating your own per-cpu allocation hint separately makes for an awkward API. Instead, allocate the per-cpu hint as part of the struct sbitmap_queue. There's no point for a struct sbitmap_queue without the cache, but you can still use a bare struct sbitmap. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17sbitmap: allocate wait queues on a specific nodeOmar Sandoval1-1/+1
The original bt_alloc() we converted from was using kzalloc(), not kzalloc_node(), to allocate the wait queues. This was probably an oversight, so fix it for sbitmap_queue_init_node(). Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-09-17blk-mq: abstract tag allocation out into sbitmap libraryOmar Sandoval1-0/+301
This is a generally useful data structure, so make it available to anyone else who might want to use it. It's also a nice cleanup separating the allocation logic from the rest of the tag handling logic. The code is behind a new Kconfig option, CONFIG_SBITMAP, which is only selected by CONFIG_BLOCK for now. This should be a complete noop functionality-wise. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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