I'm seeing the attached message generated from this line:
btrfs_debug_in_rcu(fs_info,
"btrfs_map_bio: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
bio_op(bio), bio->bi_opf, (u64)bio->bi_iter.bi_sector,
(u_long)dev->bdev->bd_dev, rcu_str_deref(dev->name), dev->devid,
bio->bi_iter.bi_size);
in submit_stripe_bio(). I'm not sure exactly why, but I suspect
rcu_str_deref() is the point from where it is generated.
Note that the mount succeeds.
This code was introduced by:
commit 672d599041c862dd61a1576c32e946ef0d77aa34
Author: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxxxxx>
Date: Thu Aug 2 16:19:07 2018 +0900
David
---
=============================
WARNING: suspicious RCU usage
4.18.0-fscache+ #540 Not tainted
-----------------------------
fs/btrfs/volumes.c:6114 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by mount/3194:
#0: 0000000072604777 (&fc->fs_type->s_umount_key#54/1){+.+.}, at: alloc_super+0xa4/0x313
stack backtrace:
CPU: 2 PID: 3194 Comm: mount Not tainted 4.18.0-fscache+ #540
Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
Call Trace:
dump_stack+0x67/0x8e
btrfs_map_bio+0x282/0x321
btree_submit_bio_hook+0x71/0xa6
submit_one_bio+0x55/0x66
read_extent_buffer_pages+0x1ec/0x2ab
btree_read_extent_buffer_pages+0x6e/0x237
? alloc_extent_buffer+0x28f/0x2f2
read_tree_block+0x43/0x5e
open_ctree+0x139b/0x1ee4
btrfs_get_tree+0x357/0xa33
? selinux_fs_context_dup+0x2d/0x104
vfs_get_tree+0x7a/0x162
btrfs_mount_root+0x52/0x8b
btrfs_get_tree+0x4ab/0xa33
? vfs_parse_fs_string+0x5b/0x9e
vfs_get_tree+0x7a/0x162
do_mount+0x7f0/0x8b2
? memdup_user+0x3e/0x5a
ksys_mount+0x72/0x97
__x64_sys_mount+0x21/0x24
do_syscall_64+0x7d/0x1a0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f11b8365ada
Code: 48 8b 0d c9 a3 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 96 a3 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe0d9a5b98 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00005562bf7702a0 RCX: 00007f11b8365ada
RDX: 00005562bf77a620 RSI: 00005562bf7704a0 RDI: 00005562bf770480
RBP: 0000000000000000 R08: 0000000000000000 R09: 00007f11b8620c40
R10: 00000000c0ed0000 R11: 0000000000000246 R12: 00005562bf770480
R13: 00005562bf77a620 R14: 0000000000000000 R15: 00007f11b90f9184
