linux/block/elevator.c, branch v5.14

blk: Fix lock inversion between ioc lock and bfqd lock

2021-06-25T00:43:55Z

Lockdep complains about lock inversion between ioc->lock and bfqd->lock: bfqd -> ioc: put_io_context+0x33/0x90 -> ioc->lock grabbed blk_mq_free_request+0x51/0x140 blk_put_request+0xe/0x10 blk_attempt_req_merge+0x1d/0x30 elv_attempt_insert_merge+0x56/0xa0 blk_mq_sched_try_insert_merge+0x4b/0x60 bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed blk_mq_sched_insert_requests+0xd6/0x2b0 blk_mq_flush_plug_list+0x154/0x280 blk_finish_plug+0x40/0x60 ext4_writepages+0x696/0x1320 do_writepages+0x1c/0x80 __filemap_fdatawrite_range+0xd7/0x120 sync_file_range+0xac/0xf0 ioc->bfqd: bfq_exit_icq+0xa3/0xe0 -> bfqd->lock grabbed put_io_context_active+0x78/0xb0 -> ioc->lock grabbed exit_io_context+0x48/0x50 do_exit+0x7e9/0xdd0 do_group_exit+0x54/0xc0 To avoid this inversion we change blk_mq_sched_try_insert_merge() to not free the merged request but rather leave that upto the caller similarly to blk_mq_sched_try_merge(). And in bfq_insert_requests() we make sure to free all the merged requests after dropping bfqd->lock. Fixes: aee69d78dec0 ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler") Reviewed-by: Ming Lei Acked-by: Paolo Valente Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20210623093634.27879-3-jack@suse.cz Signed-off-by: Jens Axboe

block: Remove unnecessary elevator operation checks

2021-06-18T14:51:48Z

The insert_requests and dispatch_request elevator operations are mandatory for the correct execution of an elevator, and all implemented elevators (bfq, kyber and mq-deadline) implement them. As a result, there is no need to check for these operations before calling them when a queue has an elevator set. This simplifies the code in __blk_mq_sched_dispatch_requests() and blk_mq_sched_insert_request(). To avoid out-of-tree elevators to crash the kernel in case of bad implementation, add a check in elv_register() to verify that these operations are implemented. A small, probably not significant, IOPS improvement of 0.1% is observed with this patch applied (4.117 MIOPS to 4.123 MIOPS, average of 20 fio runs doing 4K random direct reads with psync and 32 jobs). Signed-off-by: Damien Le Moal Reviewed-by: Johannes Thumshirn Link: https://lore.kernel.org/r/20210618015922.713999-1-damien.lemoal@wdc.com Signed-off-by: Jens Axboe

blk-mq: improve the blk_mq_init_allocated_queue interface

2021-06-11T17:53:02Z

Don't return the passed in request_queue but a normal error code, and drop the elevator_init argument in favor of just calling elevator_init_mq directly from dm-rq. Signed-off-by: Christoph Hellwig Reviewed-by: Chaitanya Kulkarni Link: https://lore.kernel.org/r/20210602065345.355274-3-hch@lst.de Signed-off-by: Jens Axboe

blk-mq: set default elevator as deadline in case of hctx shared tagset

2021-04-07T16:15:23Z

Yanhui found that write performance is degraded a lot after applying hctx shared tagset on one test machine with megaraid_sas. And turns out it is caused by none scheduler which becomes default elevator caused by hctx shared tagset patchset. Given more scsi HBAs will apply hctx shared tagset, and the similar performance exists for them too. So keep previous behavior by still using default mq-deadline for queues which apply hctx shared tagset, just like before. Fixes: 32bc15afed04 ("blk-mq: Facilitate a shared sbitmap per tagset") Reported-by: Yanhui Ma Cc: John Garry Cc: Hannes Reinecke Signed-off-by: Ming Lei Reviewed-by: Martin K. Petersen Reviewed-by: Bart Van Assche Reviewed-by: John Garry Link: https://lore.kernel.org/r/20210406031933.767228-1-ming.lei@redhat.com Signed-off-by: Jens Axboe

block: fix comment and add lockdep assert

2020-10-09T18:34:06Z

After commit b89f625e28d4 ("block: don't release queue's sysfs lock during switching elevator"), whole elevator register and unregister function are covered by sysfs_lock. So, remove wrong comment and add lockdep assert. Signed-off-by: Yufen Yu Signed-off-by: Jens Axboe

block: use helper function to test queue register

2020-10-09T18:34:06Z

We have defined common interface blk_queue_registered() to test QUEUE_FLAG_REGISTERED. Just use it. Signed-off-by: Yufen Yu Signed-off-by: Jens Axboe

block: remove redundant mq check

2020-10-09T18:34:06Z

elv_support_iosched() will check queue_is_mq() for us. So, remove the redundant check to clean code. Signed-off-by: Yufen Yu Signed-off-by: Jens Axboe

block: invoke blk_mq_exit_sched no matter whether have .exit_sched

2020-10-09T18:34:06Z

We will register debugfs for scheduler no matter whether it have defined callback funciton .exit_sched. So, blk_mq_exit_sched() is always needed to unregister debugfs. Also, q->elevator should be set as NULL after exiting scheduler. For now, since all register scheduler have defined .exit_sched, it will not cause any actual problem. But It will be more reasonable to do this change. Signed-off-by: Yufen Yu Signed-off-by: Jens Axboe

block: elevator: delete duplicated word and fix typos

2020-07-31T22:29:47Z

Drop the repeated word "the". Fix typos of "features" and "specified". Signed-off-by: Randy Dunlap Cc: Jens Axboe Cc: linux-block@vger.kernel.org Signed-off-by: Jens Axboe

Merge branch 'for-linus' into for-5.5/block

2019-11-07T19:27:19Z

Pull on for-linus to resolve what otherwise would have been a conflict with the cgroups rstat patchset from Tejun. * for-linus: (942 commits) blkcg: make blkcg_print_stat() print stats only for online blkgs nvme: change nvme_passthru_cmd64 to explicitly mark rsvd nvme-multipath: fix crash in nvme_mpath_clear_ctrl_paths nvme-rdma: fix a segmentation fault during module unload iocost: don't nest spin_lock_irq in ioc_weight_write() io_uring: ensure we clear io_kiocb->result before each issue um-ubd: Entrust re-queue to the upper layers nvme-multipath: remove unused groups_only mode in ana log nvme-multipath: fix possible io hang after ctrl reconnect io_uring: don't touch ctx in setup after ring fd install io_uring: Fix leaked shadow_req Linux 5.4-rc5 riscv: cleanup do_trap_break nbd: verify socket is supported during setup ata: libahci_platform: Fix regulator_get_optional() misuse nbd: handle racing with error'ed out commands nbd: protect cmd->status with cmd->lock io_uring: fix bad inflight accounting for SETUP_IOPOLL|SETUP_SQTHREAD io_uring: used cached copies of sq->dropped and cq->overflow ARM: dts: stm32: relax qspi pins slew-rate for stm32mp157 ...