linux-kernel - [syzbot] [ext4?] WARNING in ext4_split_convert

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Message-ID: <69741ffa.050a0220.1a75db.0328.GAE@google.com>
Date: Fri, 23 Jan 2026 17:27:22 -0800
From: syzbot <syzbot+e625b79bfdd66c067432@...kaller.appspotmail.com>
To: adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, tytso@....edu
Subject: [syzbot] [ext4?] WARNING in ext4_split_convert_extents

Hello,

syzbot found the following issue on:

HEAD commit:    d08c85ac8894 Add linux-next specific files for 20260119
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=171a1852580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ee3bfbe9e319ed0c
dashboard link: https://syzkaller.appspot.com/bug?extid=e625b79bfdd66c067432
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=121533fa580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12bc7b9a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/94cfdbd8a0c9/disk-d08c85ac.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f7ec0695ac29/vmlinux-d08c85ac.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ddc8307e03e3/bzImage-d08c85ac.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/6ddc9a8efbb6/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=14f96bfc580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e625b79bfdd66c067432@...kaller.appspotmail.com

------------[ cut here ]------------
WARNING: fs/ext4/extents.c:3486 at ext4_split_extent fs/ext4/extents.c:3485 [inline], CPU#1: kworker/u8:4/58
WARNING: fs/ext4/extents.c:3486 at ext4_split_convert_extents+0x13c2/0x1a10 fs/ext4/extents.c:3839, CPU#1: kworker/u8:4/58
Modules linked in:
CPU: 1 UID: 0 PID: 58 Comm: kworker/u8:4 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
RIP: 0010:ext4_split_extent fs/ext4/extents.c:3485 [inline]
RIP: 0010:ext4_split_convert_extents+0x13c2/0x1a10 fs/ext4/extents.c:3839
Code: 4c 8b 44 24 38 e8 be 85 fe ff 40 b5 01 4c 8b 64 24 18 49 81 fc 00 f0 ff ff 0f 87 19 ff ff ff e9 4e f0 ff ff e8 3f 8f 4a ff 90 <0f> 0b 90 49 bf 00 00 00 00 00 fc ff df 44 8b 6c 24 04 4c 8b 64 24
RSP: 0018:ffffc900015f7328 EFLAGS: 00010293
RAX: ffffffff82768aa1 RBX: dffffc0000000001 RCX: ffff88801cb99e40
RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000008
RBP: 0000000000000008 R08: ffff88802ba1269f R09: 0000000000000000
R10: ffff88802ba12690 R11: ffffed10057424d4 R12: 0000000000000010
R13: ffff888073634d01 R14: 0000000000000010 R15: 0000000000000100
FS:  0000000000000000(0000) GS:ffff888125cf2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000080 CR3: 000000000df3e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ext4_convert_unwritten_extents_endio fs/ext4/extents.c:3915 [inline]
 ext4_ext_handle_unwritten_extents fs/ext4/extents.c:3999 [inline]
 ext4_ext_map_blocks+0xde4/0x5560 fs/ext4/extents.c:4336
 ext4_map_create_blocks+0x11d/0x540 fs/ext4/inode.c:616
 ext4_map_blocks+0x759/0x1170 fs/ext4/inode.c:809
 ext4_convert_unwritten_extents+0x2a8/0x5d0 fs/ext4/extents.c:5038
 ext4_convert_unwritten_io_end_vec+0xff/0x170 fs/ext4/extents.c:5078
 ext4_end_io_end+0xc7/0x410 fs/ext4/page-io.c:200
 ext4_do_flush_completed_IO fs/ext4/page-io.c:291 [inline]
 ext4_end_io_rsv_work+0x262/0x330 fs/ext4/page-io.c:306
 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3279
 process_scheduled_works kernel/workqueue.c:3362 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3443
 kthread+0x389/0x480 kernel/kthread.c:467
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
This report is generated by a bot. It may contain errors.
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