NVMe 上的页分配失败，在写回期间无法为 I/O 分配内存。

Issue

• NVMe 上的页分配失败，在写回期间无法为 I/O 分配内存。

kernel: SLUB: Unable to allocate memory on node -1 (gfp=0x20)
kernel:  cache: kmalloc-8192, object size: 8192, buffer size: 8192, default order: 3, min order: 1
kernel:  node 0: slabs: 132, objs: 489, free: 0
kernel: kworker/0:1H: page allocation failure: order:1, mode:0x204020
kernel: CPU: 0 PID: 480 Comm: kworker/0:1H Kdump: loaded Tainted: P           OE
kernel: Hardware name: HP HP Z4 G4 Workstation/81C5, BIOS P61 v01.70 10/10/2018
kernel: Workqueue: kblockd blk_mq_run_work_fn
kernel: Call Trace:
kernel: [<ffffffffa490e78e>] dump_stack+0x19/0x1b
kernel: [<ffffffffa439a130>] warn_alloc_failed+0x110/0x180
kernel: [<ffffffffa439ecb4>] __alloc_pages_nodemask+0x9b4/0xbb0
kernel: [<ffffffffa43e8868>] alloc_pages_current+0x98/0x110
kernel: [<ffffffffa43f3eec>] new_slab+0x2fc/0x310
kernel: [<ffffffffa43f577c>] ___slab_alloc+0x3ac/0x4f0
kernel: [<ffffffffc0202834>] ? nvme_queue_rq+0xb4/0x8d0 [nvme]
kernel: [<ffffffffa47a833c>] ? __domain_mapping+0x1dc/0x3b0
kernel: [<ffffffffc0202834>] ? nvme_queue_rq+0xb4/0x8d0 [nvme]
kernel: [<ffffffffa490b9d6>] __slab_alloc+0x40/0x5c
kernel: [<ffffffffa43f8670>] __kmalloc+0x1c0/0x230
kernel: [<ffffffffc0202834>] nvme_queue_rq+0xb4/0x8d0 [nvme]
kernel: [<ffffffffa42d849c>] ? update_curr+0x14c/0x1e0
kernel: [<ffffffffa45261e6>] blk_mq_dispatch_rq_list+0x96/0x640
kernel: [<ffffffffc037bcff>] ? xlog_state_do_callback+0x2af/0x2c0 [xfs]
kernel: [<ffffffffa45251c6>] ? flush_busy_ctx+0x46/0x90
kernel: [<ffffffffa452bad1>] blk_mq_sched_dispatch_requests+0x181/0x1c0
kernel: [<ffffffffa4524c92>] __blk_mq_run_hw_queue+0xa2/0xb0
kernel: [<ffffffffa4524ef5>] blk_mq_run_work_fn+0x15/0x20
kernel: [<ffffffffa42b312f>] process_one_work+0x17f/0x440
kernel: [<ffffffffa42b3df6>] worker_thread+0x126/0x3c0
kernel: [<ffffffffa42b3cd0>] ? manage_workers.isra.24+0x2a0/0x2a0
kernel: [<ffffffffa42bb161>] kthread+0xd1/0xe0
kernel: [<ffffffffa42bb090>] ? insert_kthread_work+0x40/0x40
kernel: [<ffffffffa492065d>] ret_from_fork_nospec_begin+0x7/0x21
kernel: [<ffffffffa42bb090>] ? insert_kthread_work+0x40/0x40