linux-kernel - [syzbot] [btrfs?] WARNING in __cow_file_range

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Message-ID: <68dd8512.050a0220.25d7ab.077a.GAE@google.com>
Date: Wed, 01 Oct 2025 12:46:26 -0700
From: syzbot <syzbot+e74e4a74c03733ebac54@...kaller.appspotmail.com>
To: clm@...com, dsterba@...e.com, josef@...icpanda.com, 
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [btrfs?] WARNING in __cow_file_range_inline

Hello,

syzbot found the following issue on:

HEAD commit:    fec734e8d564 Merge tag 'riscv-for-linus-v6.17-rc8' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1073b142580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=e74e4a74c03733ebac54
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-fec734e8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9cf7097db7bd/vmlinux-fec734e8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ca6d872c8346/bzImage-fec734e8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e74e4a74c03733ebac54@...kaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
BTRFS: device fsid e417788f-7a09-42b2-9266-8ddc5d5d35d2 devid 1 transid 8 /dev/loop0 (7:0) scanned by syz.0.0 (5360)
BTRFS info (device loop0): first mount of filesystem e417788f-7a09-42b2-9266-8ddc5d5d35d2
BTRFS info (device loop0): using xxhash64 (xxhash64-generic) checksum algorithm
BTRFS warning (device loop0): space cache v1 is being deprecated and will be removed in a future release, please use -o space_cache=v2
BTRFS info (device loop0): rebuilding free space tree
BTRFS info (device loop0): disabling free space tree
BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE (0x1)
BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2)
BTRFS info (device loop0): setting nodatasum
BTRFS info (device loop0): allowing degraded mounts
BTRFS info (device loop0): enabling disk space caching
BTRFS info (device loop0): force clearing of disk cache
BTRFS info (device loop0): force zlib compression, level 3
------------[ cut here ]------------
BTRFS: Transaction aborted (error -28)
WARNING: CPU: 0 PID: 5360 at fs/btrfs/inode.c:635 __cow_file_range_inline+0xdc4/0x1260 fs/btrfs/inode.c:635
Modules linked in:
CPU: 0 UID: 0 PID: 5360 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__cow_file_range_inline+0xdc4/0x1260 fs/btrfs/inode.c:635
Code: 00 e8 10 94 da fd 84 c0 74 29 e8 57 f1 f3 fd e9 6d 01 00 00 e8 4d f1 f3 fd 90 48 c7 c7 20 dd ed 8b 44 89 e6 e8 fd 80 b7 fd 90 <0f> 0b 90 90 e9 72 fc ff ff e8 6e a5 b0 07 41 89 c7 31 ff 89 c6 e8
RSP: 0018:ffffc9000d556680 EFLAGS: 00010246
RAX: 10ba3533504e6700 RBX: 0000000000000000 RCX: 0000000000100000
RDX: ffffc9000e17a000 RSI: 0000000000034014 RDI: 0000000000034015
RBP: ffffc9000d556870 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1c3a234 R12: 00000000ffffffe4
R13: 1ffff1100641d3c8 R14: ffff8880320e9e40 R15: ffff888052e34001
FS:  00007ff11f0e36c0(0000) GS:ffff88808d007000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000440 CR3: 0000000043940000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 cow_file_range_inline+0x2fc/0x3d0 fs/btrfs/inode.c:692
 cow_file_range+0x449/0x10a0 fs/btrfs/inode.c:1297
 btrfs_run_delalloc_range+0x3f9/0xf80 fs/btrfs/inode.c:2352
 writepage_delalloc+0xf06/0x1a60 fs/btrfs/extent_io.c:1435
 extent_writepage fs/btrfs/extent_io.c:1779 [inline]
 extent_write_cache_pages fs/btrfs/extent_io.c:2463 [inline]
 btrfs_writepages+0x12df/0x22c0 fs/btrfs/extent_io.c:2596
 do_writepages+0x32e/0x550 mm/page-writeback.c:2634
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 filemap_fdatawrite_range+0x1a5/0x250 mm/filemap.c:437
 btrfs_fdatawrite_range fs/btrfs/file.c:3859 [inline]
 start_ordered_ops fs/btrfs/file.c:1518 [inline]
 btrfs_sync_file+0x3a1/0x1160 fs/btrfs/file.c:1600
 generic_write_sync include/linux/fs.h:3043 [inline]
 btrfs_do_write_iter+0x59a/0x710 fs/btrfs/file.c:1470
 iter_file_splice_write+0x975/0x10e0 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x101/0x160 fs/splice.c:1161
 splice_direct_to_actor+0x5a5/0xcc0 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0x181/0x270 fs/splice.c:1230
 do_sendfile+0x4da/0x7e0 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1417
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff11e18eec9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff11f0e3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007ff11e3e5fa0 RCX: 00007ff11e18eec9
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000006
RBP: 00007ff11e211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000040001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff11e3e6038 R14: 00007ff11e3e5fa0 R15: 00007ffcc89ac948
 </TASK>


---
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