On 2/11/21 7:38 AM, David Jeffery wrote: > When a stacked block device inserts a request into another block device > using blk_insert_cloned_request, the request's nr_phys_segments field gets > recalculated by a call to blk_recalc_rq_segments in > blk_cloned_rq_check_limits. But blk_recalc_rq_segments does not know how to > handle multi-segment discards. For disk types which can handle > multi-segment discards like nvme, this results in discard requests which > claim a single segment when it should report several, triggering a warning > in nvme and causing nvme to fail the discard from the invalid state. > > WARNING: CPU: 5 PID: 191 at drivers/nvme/host/core.c:700 nvme_setup_discard+0x170/0x1e0 [nvme_core] > ... > nvme_setup_cmd+0x217/0x270 [nvme_core] > nvme_loop_queue_rq+0x51/0x1b0 [nvme_loop] > __blk_mq_try_issue_directly+0xe7/0x1b0 > blk_mq_request_issue_directly+0x41/0x70 > ? blk_account_io_start+0x40/0x50 > dm_mq_queue_rq+0x200/0x3e0 > blk_mq_dispatch_rq_list+0x10a/0x7d0 > ? __sbitmap_queue_get+0x25/0x90 > ? elv_rb_del+0x1f/0x30 > ? deadline_remove_request+0x55/0xb0 > ? dd_dispatch_request+0x181/0x210 > __blk_mq_do_dispatch_sched+0x144/0x290 > ? bio_attempt_discard_merge+0x134/0x1f0 > __blk_mq_sched_dispatch_requests+0x129/0x180 > blk_mq_sched_dispatch_requests+0x30/0x60 > __blk_mq_run_hw_queue+0x47/0xe0 > __blk_mq_delay_run_hw_queue+0x15b/0x170 > blk_mq_sched_insert_requests+0x68/0xe0 > blk_mq_flush_plug_list+0xf0/0x170 > blk_finish_plug+0x36/0x50 > xlog_cil_committed+0x19f/0x290 [xfs] > xlog_cil_process_committed+0x57/0x80 [xfs] > xlog_state_do_callback+0x1e0/0x2a0 [xfs] > xlog_ioend_work+0x2f/0x80 [xfs] > process_one_work+0x1b6/0x350 > worker_thread+0x53/0x3e0 > ? process_one_work+0x350/0x350 > kthread+0x11b/0x140 > ? __kthread_bind_mask+0x60/0x60 > ret_from_fork+0x22/0x30 > > This patch fixes blk_recalc_rq_segments to be aware of devices which can > have multi-segment discards. It calculates the correct discard segment > count by counting the number of bio as each discard bio is considered its > own segment. Applied, thanks. -- Jens Axboe
