On Wed, Aug 27, 2025 at 6:45 AM Aleksandr Nogikh <nogikh@xxxxxxxxxx> wrote: > > I've bisected the problem to the following commit: > > commit 167f21a81a9c4dbd6970a4ee3853aecad405fa7f (HEAD) > Author: Joanne Koong <joannelkoong@xxxxxxxxx> > Date: Mon Jul 7 16:46:06 2025 -0700 > > mm: remove BDI_CAP_WRITEBACK_ACCT > > There are no users of BDI_CAP_WRITEBACK_ACCT now that fuse doesn't do > its own writeback accounting. This commit removes > BDI_CAP_WRITEBACK_ACCT. > > Joanne Koong, could you please take a look at the syzbot report below? Hi Aleksandr, Thanks for bisecting this. This is a duplicate of what Marek reported in [1]. His patch in [2] fixes the warning getting triggered. Marek, could you submit your patch formally to the mm tree so it could be picked up? Thanks, Joanne [1] https://lore.kernel.org/linux-fsdevel/a91010a8-e715-4f3d-9e22-e4c34efc0408@xxxxxxxxxxx/T/#u [2] https://lore.kernel.org/linux-fsdevel/a91010a8-e715-4f3d-9e22-e4c34efc0408@xxxxxxxxxxx/T/#m3aa6506ee7de302242e64861f8e2199f24e4ad46 > > On Fri, Aug 22, 2025 at 12:09 PM syzbot > <syzbot+0630e71306742d4b2aea@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 0f4c93f7eb86 Add linux-next specific files for 20250822 > > git tree: linux-next > > console output: https://syzkaller.appspot.com/x/log.txt?x=172c07bc580000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=21eed27c0deadb92 > > dashboard link: https://syzkaller.appspot.com/bug?extid=0630e71306742d4b2aea > > compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7 > > > > Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/669ede8f5d66/disk-0f4c93f7.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/50feda89fe89/vmlinux-0f4c93f7.xz > > kernel image: https://storage.googleapis.com/syzbot-assets/317a0d3516fb/bzImage-0f4c93f7.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+0630e71306742d4b2aea@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ------------[ cut here ]------------ > > WARNING: ./include/linux/backing-dev.h:243 at inode_to_wb include/linux/backing-dev.h:239 [inline], CPU#1: kworker/u8:6/2949 > > WARNING: ./include/linux/backing-dev.h:243 at __folio_start_writeback+0x9d5/0xb70 mm/page-writeback.c:3027, CPU#1: kworker/u8:6/2949 > > Modules linked in: > > CPU: 1 UID: 0 PID: 2949 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT(full) > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 > > Workqueue: writeback wb_workfn (flush-8:0) > > RIP: 0010:inode_to_wb include/linux/backing-dev.h:239 [inline] > > RIP: 0010:__folio_start_writeback+0x9d5/0xb70 mm/page-writeback.c:3027 > > Code: 28 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 ff e8 ce a2 29 00 49 8b 07 25 ff 3f 00 00 e9 1b fa ff ff e8 7c 04 c6 ff 90 <0f> 0b 90 e9 d6 fb ff ff e8 6e 04 c6 ff 48 c7 c7 a0 f8 5f 8e 4c 89 > > RSP: 0018:ffffc9000bb06ea0 EFLAGS: 00010293 > > RAX: ffffffff81fad344 RBX: ffffea00050de8c0 RCX: ffff88802ee29e00 > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 > > RBP: ffffc9000bb07010 R08: ffffc9000bb06f97 R09: 0000000000000000 > > R10: ffffc9000bb06f80 R11: fffff52001760df3 R12: ffffea00050de8c8 > > R13: 0000000000000000 R14: ffff888023060880 R15: ffff888023060660 > > FS: 0000000000000000(0000) GS:ffff8881258c3000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00007f7354907000 CR3: 000000000e338000 CR4: 00000000003526f0 > > Call Trace: > > <TASK> > > __block_write_full_folio+0x75f/0xe10 fs/buffer.c:1928 > > blkdev_writepages+0xd1/0x170 block/fops.c:484 > > do_writepages+0x32e/0x550 mm/page-writeback.c:2604 > > __writeback_single_inode+0x145/0xff0 fs/fs-writeback.c:1680 > > writeback_sb_inodes+0x6c7/0x1010 fs/fs-writeback.c:1976 > > __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:2047 > > wb_writeback+0x44f/0xaf0 fs/fs-writeback.c:2158 > > wb_check_old_data_flush fs/fs-writeback.c:2262 [inline] > > wb_do_writeback fs/fs-writeback.c:2315 [inline] > > wb_workfn+0xaef/0xef0 fs/fs-writeback.c:2343 > > process_one_work kernel/workqueue.c:3236 [inline] > > process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319 > > worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400 > > kthread+0x711/0x8a0 kernel/kthread.c:463 > > ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148 > > 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. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > > > syzbot will keep track of this issue. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > > > If the report is already addressed, let syzbot know by replying with: > > #syz fix: exact-commit-title > > > > If you want to overwrite report's subsystems, reply with: > > #syz set subsystems: new-subsystem > > (See the list of subsystem names on the web dashboard) > > > > If the report is a duplicate of another one, reply with: > > #syz dup: exact-subject-of-another-report > > > > If you want to undo deduplication, reply with: > > #syz undup > >
