WARNING in btrfs_add_link

Status: upstream: reported on 2026/10/02 14:54
Reported-by: syzbot+60ba5199442677a40b63@syzkaller.appspotmail.com
First crash: 5d03h, last: 5d03h
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in btrfs_add_link (3) prio:high btrfs -1 5 10d 39d 0/29 upstream: reported on 2026/08/29 06:51
upstream WARNING in btrfs_add_link btrfs -1 syz, C error unreliable 7 1430d 1450d 0/29 auto-obsoleted due to no activity on 2023/07/21 23:31
upstream WARNING in btrfs_add_link (2) btrfs -1 1 229d 225d 0/29 auto-obsoleted due to no activity on 2026/05/30 22:47
linux-5.15 WARNING in btrfs_add_link -1 1 1258d 1258d 0/3 auto-obsoleted due to no activity on 2023/08/23 09:04
linux-5.15 WARNING in btrfs_add_link (2) origin:lts-only -1 syz, C error 10 35d 802d 0/3 upstream: reported C repro on 2024/07/27 06:25

Sample crash report:
------------[ 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

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/02 14:54 linux-6.1.y 1a8763b93150 6d32eb1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in btrfs_add_link
* Struck through repros no longer work on HEAD.