[v6.1] WARNING in btrfs_add_link

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1a8763b93150 Linux 6.1.188
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13ee0bf5580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e5b41322189806a
dashboard link: https://syzkaller.appspot.com/bug?extid=60ba5199442677a40b63
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79d582e9ec4f/disk-1a8763b9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70e43b512b19/vmlinux-1a8763b9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7107d5b60093/Image-1a8763b9.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+60ba51...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 16107 at fs/btrfs/inode.c:6795 btrfs_add_link+0x7d0/0xa40 fs/btrfs/inode.c:6795
Modules linked in:
CPU: 0 PID: 16107 Comm: syz.8.2925 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : btrfs_add_link+0x7d0/0xa40 fs/btrfs/inode.c:6795
lr : btrfs_add_link+0x7d0/0xa40 fs/btrfs/inode.c:6795
sp : ffff800021d47320
x29: ffff800021d47420
x28: ffff0000e17d70a8 x27: 0000000000000107
x26: 0000000000000007 x25: dfff800000000000 x24: 0000000000000000
x23: 1fffe0001c2fae1f x22: ffff0000e17d70f8 x21: 0000000000000000
x20: 00000000ffffffe4 x19: ffff7000043a8e6c x18: 1fffe00033e6997e
x17: ffff8000153bd000 x16: ffff8000082dd284 x15: 0000000040000000
x14: 0000000000000001 x13: 1fffe00033e6c070 x12: 0000000000000000
x11: ff0080000a97ca20 x10: 0000000000000003 x9 : 2a63c418b8da4e00
x8 : 2a63c418b8da4e00 x7 : ffff80000825ab20 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000007 x1 : ffff800011d1dc80 x0 : ffff80018a036000
Call trace:
btrfs_add_link+0x7d0/0xa40 fs/btrfs/inode.c:6795
btrfs_create_new_inode+0x1464/0x20f8 fs/btrfs/inode.c:6731
btrfs_create_common+0x16c/0x240 fs/btrfs/inode.c:6866
btrfs_create+0x10c/0x130 fs/btrfs/inode.c:6906
lookup_open fs/namei.c:3533 [inline]
open_last_lookups fs/namei.c:3601 [inline]
path_openat+0xda8/0x27a0 fs/namei.c:3831
do_filp_open+0x198/0x38c fs/namei.c:3861
do_sys_openat2+0x134/0x3fc fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__arm64_sys_openat+0x11c/0x150 fs/open.c:1347
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 932
hardirqs last enabled at (931): [<ffff80000825abb4>] raw_spin_rq_unlock_irq kernel/sched/sched.h:1374 [inline]
hardirqs last enabled at (931): [<ffff80000825abb4>] finish_lock_switch+0xb0/0x1c8 kernel/sched/core.c:5005
hardirqs last disabled at (932): [<ffff800011bb2834>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last enabled at (564): [<ffff8000081ae3b4>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last enabled at (564): [<ffff8000081ae3b4>] handle_softirqs+0xb1c/0xc90 kernel/softirq.c:624
softirqs last disabled at (199): [<ffff800008020e6c>] __do_softirq+0x14/0x20 kernel/softirq.c:630
---[ end trace 0000000000000000 ]---
BTRFS info (device loop8: state A): dumping space info:
BTRFS info (device loop8: state A): space_info DATA+METADATA (sub-group id 0) has 6733824 free, is full
BTRFS info (device loop8: state A): space_info total=11534336, used=61440, pinned=20480, reserved=0, may_use=3080192, readonly=1638400 zone_unusable=0
BTRFS info (device loop8: state A): space_info SYSTEM (sub-group id 0) has 4186112 free, is not full
BTRFS info (device loop8: state A): space_info total=4194304, used=4096, pinned=4096, reserved=0, may_use=0, readonly=0 zone_unusable=0
BTRFS info (device loop8: state A): global_block_rsv: size 1441792 reserved 1441792
BTRFS info (device loop8: state A): trans_block_rsv: size 327680 reserved 327680
BTRFS info (device loop8: state A): chunk_block_rsv: size 0 reserved 0
BTRFS info (device loop8: state A): delayed_block_rsv: size 0 reserved 0
BTRFS info (device loop8: state A): delayed_refs_rsv: size 262144 reserved 262144
BTRFS: error (device loop8: state A) in btrfs_add_link:6795: errno=-28 No space left
BTRFS info (device loop8: state EA): forced readonly
BTRFS: error (device loop8: state EA) in btrfs_create_new_inode:6735: errno=-28 No space left


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