Re: [syzbot] [f2fs?] possible deadlock in f2fs_fiemap

[Chao Yu]

On 2023/6/26 1:45, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    15e71592dbae Add linux-next specific files for 20230621
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=101c827b280000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b4e51841f618f374
> dashboard link: https://syzkaller.appspot.com/bug?extid=dd6352699b8027673b35
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/6b6464ef4887/disk-15e71592.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/81eba5775318/vmlinux-15e71592.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/bc7983587629/bzImage-15e71592.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+dd6352699b8027673b35@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> loop4: detected capacity change from 0 to 40427
> F2FS-fs (loop4): Found nat_bits in checkpoint
> F2FS-fs (loop4): Mounted with checkpoint version = 48b305e5
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.4.0-rc7-next-20230621-syzkaller #0 Not tainted
> ------------------------------------------------------
> syz-executor.4/7658 is trying to acquire lock:
> ffff888012869e20 (&mm->mmap_lock){++++}-{3:3}, at: __might_fault+0xb2/0x190 mm/memory.c:5716
>
> but task is already holding lock:
> ffff8880865b1a10 (&sb->s_type->i_mutex_key#23){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:771 [inline]
> ffff8880865b1a10 (&sb->s_type->i_mutex_key#23){+.+.}-{3:3}, at: f2fs_fiemap+0x1e3/0x1670 fs/f2fs/data.c:1998

This was caused by the patch
"f2fs: fix to avoid mmap vs set_compress_option case"
(https://lore.kernel.org/linux-f2fs-devel/20230529104709.2560779-1-chao@xxxxxxxxxx/)
which has been dropped.

#syz set subsystems: f2fs
#syz invalid