Messages in this thread | | | Date | Thu, 28 Jan 2021 10:40:04 +0100 | From | Daniel Wagner <> | Subject | Re: [PATCH v2] nvme-multipath: Early exit if no path is available |
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On Thu, Jan 28, 2021 at 05:18:56PM +0800, Chao Leng wrote: > It is impossible to return NULL for nvme_next_ns(head, old).
block nvme0n1: no usable path - requeuing I/O block nvme0n1: no usable path - requeuing I/O block nvme0n1: no usable path - requeuing I/O block nvme0n1: no usable path - requeuing I/O block nvme0n1: no usable path - requeuing I/O block nvme0n1: no usable path - requeuing I/O BUG: kernel NULL pointer dereference, address: 0000000000000068 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 8000000ff67bc067 P4D 8000000ff67bc067 PUD ff9ac9067 PMD 0 Oops: 0000 [#1] SMP PTI CPU: 23 PID: 15759 Comm: dt.21.15 Kdump: loaded Tainted: G E 5.3.18-0.gc9fe679-default #1 SLE15-SP2 (unreleased) Hardware name: FUJITSU PRIMERGY RX2540 M2/D3289-B1, BIOS V5.0.0.11 R1.18.0 for D3289-B1x 02/06/2018 RIP: 0010:nvme_ns_head_make_request+0x1d1/0x430 [nvme_core] Code: 54 24 10 0f 84 c9 01 00 00 48 8b 54 24 10 48 83 ea 30 0f 84 ba 01 00 00 48 39 d0 0f 84 01 02 00 00 31 ff eb 05 48 39 d0 74 67 <48> 8b 72 68 83 e6 04 75 13 48 8b 72 68 83 e6 01 75 0a 48 8b 72 10 RSP: 0018:ffffa69d08017af8 EFLAGS: 00010246 RAX: ffff92f261d87800 RBX: ffff92fa555b0010 RCX: ffff92fa555bc570 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000001 R08: 0000000000001000 R09: 0000000000001000 R10: ffffa69d080179a8 R11: ffff92f264f0c1c0 R12: ffff92f264f7f000 R13: ffff92fa555b0000 R14: 0000000000000001 R15: 0000000000000000 FS: 00007f3962bae700(0000) GS:ffff92f29ffc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000068 CR3: 0000000fd69a2002 CR4: 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: generic_make_request+0x121/0x300 ? submit_bio+0x42/0x1c0 submit_bio+0x42/0x1c0 ext4_io_submit+0x49/0x60 [ext4] ext4_writepages+0x625/0xe90 [ext4] ? do_writepages+0x4b/0xe0 ? ext4_mark_inode_dirty+0x1d0/0x1d0 [ext4] do_writepages+0x4b/0xe0 ? __generic_file_write_iter+0x192/0x1c0 ? __filemap_fdatawrite_range+0xcb/0x100 __filemap_fdatawrite_range+0xcb/0x100 ? ext4_file_write_iter+0x128/0x3c0 [ext4] file_write_and_wait_range+0x5e/0xb0 __generic_file_fsync+0x22/0xb0 ext4_sync_file+0x1f7/0x3c0 [ext4] do_fsync+0x38/0x60 __x64_sys_fsync+0x10/0x20 do_syscall_64+0x5b/0x1e0 entry_SYSCALL_64_after_hwframe+0x44/0xa9
You can't see exactly where it dies but I followed the assembly to nvme_round_robin_path(). Maybe it's not the initial nvme_next_ns(head, old) which returns NULL but nvme_next_ns() is returning NULL eventually (list_next_or_null_rcu()).
And I have positive feedback, this patch fixes the above problem.
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