[syzbot] BUG: spinlock bad magic in erofs_pcpubuf_growsize

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9c54130c Add linux-next specific files for 20210406
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1654617ed00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d125958c3995ddcd
dashboard link: https://syzkaller.appspot.com/bug?extid=d6a0e4b80bd39f54c2f6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=101a5786d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1147dd0ed00000

The issue was bisected to:

commit 997acaf6b4b59c6a9c259740312a69ea549cc684
Author: Mark Rutland <mark.rutland@xxxxxxx>
Date:   Mon Jan 11 15:37:07 2021 +0000

    lockdep: report broken irq restoration

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11d8d7aad00000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=13d8d7aad00000
console output: https://syzkaller.appspot.com/x/log.txt?x=15d8d7aad00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d6a0e4b80bd39f54c2f6@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 997acaf6b4b5 ("lockdep: report broken irq restoration")

loop0: detected capacity change from 0 to 31
BUG: spinlock bad magic on CPU#1, syz-executor062/8434
 lock: 0xffff8880b9c31d60, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
CPU: 1 PID: 8434 Comm: syz-executor062 Not tainted 5.12.0-rc6-next-20210406-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline]
 do_raw_spin_lock+0x216/0x2b0 kernel/locking/spinlock_debug.c:112
 erofs_pcpubuf_growsize+0x36f/0x620 fs/erofs/pcpubuf.c:83
 z_erofs_load_lz4_config+0x1ef/0x3e0 fs/erofs/decompressor.c:64
 erofs_read_superblock fs/erofs/super.c:331 [inline]
 erofs_fc_fill_super+0xe84/0x1d10 fs/erofs/super.c:499
 get_tree_bdev+0x440/0x760 fs/super.c:1293
 vfs_get_tree+0x89/0x2f0 fs/super.c:1498
 do_new_mount fs/namespace.c:2905 [inline]
 path_mount+0x132a/0x1fa0 fs/namespace.c:3235
 do_mount fs/namespace.c:3248 [inline]
 __do_sys_mount fs/namespace.c:3456 [inline]
 __se_sys_mount fs/namespace.c:3433 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3433
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x444f7a
Code: 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 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 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe1fa3c2a8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe1fa3c300 RCX: 0000000000444f7a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffe1fa3c2c0
RBP: 00007ffe1fa3c2c0 R08: 00007ffe1fa3c300 R09: 


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