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Date:   Tue, 01 Aug 2023 22:35:31 -0700
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Subject: Re: [syzbot] [btrfs?] kernel BUG in prepare_to_merge
From:   syzbot <syzbot+ae97a827ae1c3336bbb4@syzkaller.appspotmail.com>
To:     clm@fb.com, dsterba@suse.com, josef@toxicpanda.com,
        linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, nogikh@google.com,
        quwenruo.btrfs@gmx.com, syzkaller-bugs@googlegroups.com
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Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in prepare_to_merge

------------[ cut here ]------------
BTRFS: Transaction aborted (error -117)
WARNING: CPU: 2 PID: 8050 at fs/btrfs/relocation.c:1946 prepare_to_merge+0x10e0/0x1460 fs/btrfs/relocation.c:1946
Modules linked in:
CPU: 2 PID: 8050 Comm: syz-executor.0 Not tainted 6.5.0-rc3-syzkaller-g8b6f9b585045 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:prepare_to_merge+0x10e0/0x1460 fs/btrfs/relocation.c:1946
Code: 8b 7e 50 44 89 e2 48 c7 c6 20 d8 b6 8a e8 28 1d 10 00 eb c1 e8 d1 83 00 fe be 8b ff ff ff 48 c7 c7 80 d7 b6 8a e8 f0 4b c7 fd <0f> 0b e9 bf fe ff ff 48 8b 7c 24 28 e8 af 93 53 fe e9 3e f5 ff ff
RSP: 0018:ffffc90022d4f6b0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff88804485e440 RCX: 0000000000000000
RDX: ffff888031a78480 RSI: ffffffff814c5346 RDI: 0000000000000001
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 000000002d2d2d2d R12: 0000000000000000
R13: 0000000000000084 R14: ffff88804485e3f0 R15: ffff88801d0eb000
FS:  00007f6a3df146c0(0000) GS:ffff88806b800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0a76ac56be CR3: 00000000300a1000 CR4: 0000000000350ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 relocate_block_group+0x8d1/0xe70 fs/btrfs/relocation.c:3779
 btrfs_relocate_block_group+0x714/0xd90 fs/btrfs/relocation.c:4117
 btrfs_relocate_chunk+0x143/0x440 fs/btrfs/volumes.c:3277
 __btrfs_balance fs/btrfs/volumes.c:4012 [inline]
 btrfs_balance+0x20fc/0x3ef0 fs/btrfs/volumes.c:4389
 btrfs_ioctl_balance fs/btrfs/ioctl.c:3604 [inline]
 btrfs_ioctl+0x1362/0x5cf0 fs/btrfs/ioctl.c:4637
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f6a3d27cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6a3df140c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6a3d39bf80 RCX: 00007f6a3d27cae9
RDX: 00000000200003c0 RSI: 00000000c4009420 RDI: 0000000000000005
RBP: 00007f6a3d2c847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f6a3d39bf80 R15: 00007ffd18ee1568
 </TASK>


Tested on:

commit:         8b6f9b58 btrfs: reject invalid reloc tree root keys
git tree:       https://github.com/adam900710/linux graceful_reloc_mismatch
console output: https://syzkaller.appspot.com/x/log.txt?x=115ab96ea80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=23c579cf0ae1addd
dashboard link: https://syzkaller.appspot.com/bug?extid=ae97a827ae1c3336bbb4
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.