Re: [syzbot] WARNING in btrfs_add_link

[syzbot <syzbot+b531e31d583db14070d4@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    b229b6ca5abb Merge tag 'perf-tools-fixes-for-v6.1-2022-10-..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11afbf6a880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1d3548a4365ba17d
dashboard link: https://syzkaller.appspot.com/bug?extid=b531e31d583db14070d4
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=124ae5f6880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1008c991880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/24728b72a896/disk-b229b6ca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/10a3c40c60e1/vmlinux-b229b6ca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/69f963b02b7e/bzImage-b229b6ca.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/fefdce45ff1c/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b531e31d583db14070d4@syzkaller.appspotmail.com

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WARNING: CPU: 1 PID: 3605 at fs/btrfs/inode.c:6568 btrfs_add_link+0x862/0xca0 fs/btrfs/inode.c:6568
Modules linked in:
CPU: 0 PID: 3605 Comm: syz-executor377 Not tainted 6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
RIP: 0010:btrfs_add_link+0x862/0xca0 fs/btrfs/inode.c:6568
Code: 40 f8 da 8a 8b 54 24 08 31 c0 e8 7b 50 a7 06 e9 21 ff ff ff e8 8f 55 fd fd 48 c7 c7 40 f7 da 8a 44 89 e6 31 c0 e8 de f3 c4 fd <0f> 0b 41 b4 01 45 0f b6 c4 48 89 df 48 c7 c6 00 ff da 8a ba a8 19
RSP: 0018:ffffc90003cff460 EFLAGS: 00010246
RAX: ade94f10cf44a400 RBX: ffff888072095150 RCX: ffff888024b7ba80
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc90003cff588 R08: ffffffff816b8dfd R09: ffffed1017364f13
R10: ffffed1017364f13 R11: 1ffff11017364f12 R12: 00000000fffffff4
R13: 00000000fffffff4 R14: ffff8880720951a0 R15: 1ffff1100e412a34
FS:  0000555556786300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000557c351539e0 CR3: 0000000076ed0000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 btrfs_create_new_inode+0x1778/0x2270 fs/btrfs/inode.c:6504
 btrfs_create_common+0x2eb/0x420 fs/btrfs/inode.c:6639
 lookup_open fs/namei.c:3413 [inline]
 open_last_lookups fs/namei.c:3481 [inline]
 path_openat+0x12d0/0x2df0 fs/namei.c:3710
 do_filp_open+0x264/0x4f0 fs/namei.c:3740
 do_sys_openat2+0x124/0x4e0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_openat fs/open.c:1342 [inline]
 __se_sys_openat fs/open.c:1337 [inline]
 __x64_sys_openat+0x243/0x290 fs/open.c:1337
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f0d1504bdd9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007fff9971cc08 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f0d1504bdd9
RDX: 000000000000275a RSI: 00000000200001c0 RDI: 00000000ffffff9c
RBP: 00007fff9971cc40 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 00007f0d1508bf00 R14: 00007fff9971cc90 R15: 0000000000000001
 </TASK>