user/sven/linux.git/include/linux/elevator.h, branch v5.15.76

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

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

kyber: fix out of bounds access when preempted

2021-05-11T14:12:14Z

__blk_mq_sched_bio_merge() gets the ctx and hctx for the current CPU and passes the hctx to ->bio_merge(). kyber_bio_merge() then gets the ctx for the current CPU again and uses that to get the corresponding Kyber context in the passed hctx. However, the thread may be preempted between the two calls to blk_mq_get_ctx(), and the ctx returned the second time may no longer correspond to the passed hctx. This "works" accidentally most of the time, but it can cause us to read garbage if the second ctx came from an hctx with more ctx's than the first one (i.e., if ctx->index_hw[hctx->type] > hctx->nr_ctx). This manifested as this UBSAN array index out of bounds error reported by Jakub: UBSAN: array-index-out-of-bounds in ../kernel/locking/qspinlock.c:130:9 index 13106 is out of range for type 'long unsigned int [128]' Call Trace: dump_stack+0xa4/0xe5 ubsan_epilogue+0x5/0x40 __ubsan_handle_out_of_bounds.cold.13+0x2a/0x34 queued_spin_lock_slowpath+0x476/0x480 do_raw_spin_lock+0x1c2/0x1d0 kyber_bio_merge+0x112/0x180 blk_mq_submit_bio+0x1f5/0x1100 submit_bio_noacct+0x7b0/0x870 submit_bio+0xc2/0x3a0 btrfs_map_bio+0x4f0/0x9d0 btrfs_submit_data_bio+0x24e/0x310 submit_one_bio+0x7f/0xb0 submit_extent_page+0xc4/0x440 __extent_writepage_io+0x2b8/0x5e0 __extent_writepage+0x28d/0x6e0 extent_write_cache_pages+0x4d7/0x7a0 extent_writepages+0xa2/0x110 do_writepages+0x8f/0x180 __writeback_single_inode+0x99/0x7f0 writeback_sb_inodes+0x34e/0x790 __writeback_inodes_wb+0x9e/0x120 wb_writeback+0x4d2/0x660 wb_workfn+0x64d/0xa10 process_one_work+0x53a/0xa80 worker_thread+0x69/0x5b0 kthread+0x20b/0x240 ret_from_fork+0x1f/0x30 Only Kyber uses the hctx, so fix it by passing the request_queue to ->bio_merge() instead. BFQ and mq-deadline just use that, and Kyber can map the queues itself to avoid the mismatch. Fixes: a6088845c2bf ("block: kyber: make kyber more friendly with merging") Reported-by: Jakub Kicinski Signed-off-by: Omar Sandoval Link: https://lore.kernel.org/r/c7598605401a48d5cfeadebb678abd10af22b83f.1620691329.git.osandov@fb.com Signed-off-by: Jens Axboe

blk-mq: Improve performance of non-mq IO schedulers with multiple HW queues

2021-01-25T01:19:46Z

Currently when non-mq aware IO scheduler (BFQ, mq-deadline) is used for a queue with multiple HW queues, the performance it rather bad. The problem is that these IO schedulers use queue-wide locking and their dispatch function does not respect the hctx it is passed in and returns any request it finds appropriate. Thus locality of request access is broken and dispatch from multiple CPUs just contends on IO scheduler locks. For these IO schedulers there's little point in dispatching from multiple CPUs. Instead dispatch always only from a single CPU to limit contention. Below is a comparison of dbench runs on XFS filesystem where the storage is a raid card with 64 HW queues and to it attached a single rotating disk. BFQ is used as IO scheduler: clients MQ SQ MQ-Patched Amean 1 39.12 (0.00%) 43.29 * -10.67%* 36.09 * 7.74%* Amean 2 128.58 (0.00%) 101.30 * 21.22%* 96.14 * 25.23%* Amean 4 577.42 (0.00%) 494.47 * 14.37%* 508.49 * 11.94%* Amean 8 610.95 (0.00%) 363.86 * 40.44%* 362.12 * 40.73%* Amean 16 391.78 (0.00%) 261.49 * 33.25%* 282.94 * 27.78%* Amean 32 324.64 (0.00%) 267.71 * 17.54%* 233.00 * 28.23%* Amean 64 295.04 (0.00%) 253.02 * 14.24%* 242.37 * 17.85%* Amean 512 10281.61 (0.00%) 10211.16 * 0.69%* 10447.53 * -1.61%* Numbers are times so lower is better. MQ is stock 5.10-rc6 kernel. SQ is the same kernel with megaraid_sas.host_tagset_enable=0 so that the card advertises just a single HW queue. MQ-Patched is a kernel with this patch applied. You can see multiple hardware queues heavily hurt performance in combination with BFQ. The patch restores the performance. Signed-off-by: Jan Kara Reviewed-by: Ming Lei Signed-off-by: Jens Axboe

blk-mq: remove the bio argument to ->prepare_request

2020-05-29T16:23:24Z

None of the I/O schedulers actually needs it. Signed-off-by: Christoph Hellwig Reviewed-by: Ming Lei Reviewed-by: Hannes Reinecke Reviewed-by: Johannes Thumshirn Reviewed-by: Bart Van Assche Reviewed-by: Daniel Wagner Signed-off-by: Jens Axboe

block: Introduce elevator features

2019-09-06T01:52:33Z

Introduce the definition of elevator features through the elevator_features flags in the elevator_type structure. Each flag can represent a feature supported by an elevator. The first feature defined by this patch is support for zoned block device sequential write constraint with the flag ELEVATOR_F_ZBD_SEQ_WRITE, which is implemented by the mq-deadline elevator using zone write locking. Other possible features are IO priorities, write hints, latency targets or single-LUN dual-actuator disks (for which the elevator could maintain one LBA ordered list per actuator). The required_elevator_features field is also added to the request_queue structure to allow a device driver to specify elevator feature flags that an elevator must support for the correct operation of the device (e.g. device drivers for zoned block devices can have the ELEVATOR_F_ZBD_SEQ_WRITE flag as a required feature). The helper function blk_queue_required_elevator_features() is defined for setting this new field. With these two new fields in place, the elevator functions elevator_match() and elevator_find() are modified to allow a user to set only an elevator with a set of features that satisfies the device required features. Elevators not matching the device requirements are not shown in the device sysfs queue/scheduler file to prevent their use. The "none" elevator can always be selected as before. Reviewed-by: Johannes Thumshirn Reviewed-by: Christoph Hellwig Reviewed-by: Ming Lei Signed-off-by: Damien Le Moal Signed-off-by: Jens Axboe

block: blk-mq: Remove blk_mq_sched_started_request and started_request

2019-07-23T13:25:09Z

blk_mq_sched_completed_request is a function that checks if the elevator related to the request has started_request implemented, but currently, none of the available IO schedulers implement started_request, so remove both. Signed-off-by: Marcos Paulo de Souza Signed-off-by: Jens Axboe

block: Fix elevator name declaration

2019-07-10T20:18:01Z

The elevator_name field in struct elevator_type is declared as an array of characters (ELV_NAME_MAX size) but in practice used as a string pointer with its initialization done statically within each elevator elevator_type structure declaration. Change the declaration of elevator_name to the more appropriate "const char *" type. Acked-by: Marcos Paulo de Souza Signed-off-by: Damien Le Moal Signed-off-by: Jens Axboe

block: Remove unused definitions

2019-07-10T20:18:01Z

The ELV_MQUEUE_XXX definitions in include/linux/elevator.h are unused since the removal of elevator_may_queue_fn in kernel 5.0. Remove these definitions and also remove the documentation of elevator_may_queue_fn in Documentiation/block/biodoc.txt. Acked-by: Marcos Paulo de Souza Signed-off-by: Damien Le Moal Signed-off-by: Jens Axboe

block: remove the bi_phys_segments field in struct bio

2019-06-20T16:29:22Z

We only need the number of segments in the blk-mq submission path. Remove the field from struct bio, and return it from a variant of blk_queue_split instead of that it can passed as an argument to those functions that need the value. This also means we stop recounting segments except for cloning and partial segments. To keep the number of arguments in this how path down remove pointless struct request_queue arguments from any of the functions that had it and grew a nr_segs argument. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe