Re: [syzbot] [btrfs?] kernel BUG in write_all_supers

[David Sterba]

On Thu, Mar 27, 2025 at 09:15:26AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    f6e0150b2003 Merge tag 'mtd/for-6.15' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1405d804580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=46a07195688b794b
> dashboard link: https://syzkaller.appspot.com/bug?extid=34122898a11ab689518a
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10d7abb0580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15d76198580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-f6e0150b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/7ade4c34c9b1/vmlinux-f6e0150b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/1fe37b97ec9d/bzImage-f6e0150b.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/1f4c759fe772/mount_0.gz
>   fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=1757abb0580000)
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+34122898a11ab689518a@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> BTRFS info (device loop0): using sha256 (sha256-avx2) checksum algorithm
> BTRFS info (device loop0): using free-space-tree
> assertion failed: folio_order(folio) == 0, in fs/btrfs/disk-io.c:3858

This is

ASSERT(folio_order(folio) == 0);

and the folio is from device->bdev->bd_mapping.