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Date:   Sun, 26 Nov 2023 06:59:41 +0800
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Subject: Re: [syzbot] [btrfs?] WARNING in btrfs_use_block_rsv
To:     syzbot <syzbot+10d5b62a8d7046b86d22@syzkaller.appspotmail.com>,
        clm@fb.com, dsterba@suse.com, josef@toxicpanda.com,
        linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
References: <0000000000004d4716060af08a45@google.com>
Content-Language: en-US
From:   Anand Jain <anand.jain@oracle.com>
In-Reply-To: <0000000000004d4716060af08a45@google.com>
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On 25/11/2023 10:08, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit a5b8a5f9f8355d27a4f8d0afa93427f16d2f3c1e
> Author: Anand Jain <anand.jain@oracle.com>
> Date:   Thu Sep 28 01:09:47 2023 +0000
> 
>      btrfs: support cloned-device mount capability
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1446d344e80000
> start commit:   d3fa86b1a7b4 Merge tag 'net-6.7-rc3' of git://git.kernel.o..
> git tree:       upstream
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=1646d344e80000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1246d344e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6ae1a4ee971a7305
> dashboard link: https://syzkaller.appspot.com/bug?extid=10d5b62a8d7046b86d22
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1431040ce80000
> 
> Reported-by: syzbot+10d5b62a8d7046b86d22@syzkaller.appspotmail.com
> Fixes: a5b8a5f9f835 ("btrfs: support cloned-device mount capability")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection


It is completely strange that this issue bisects to the commit
a5b8a5f9f835 ('btrfs: support cloned-device mount capability').
I am unable to reproduce this as well.

-------------------
WARNING: CPU: 1 PID: 58 at fs/btrfs/block-rsv.c:523 
btrfs_use_block_rsv+0x60d/0x860 fs/btrfs/block-rsv.c:523
<snap>
Call Trace:
  <TASK>
  btrfs_alloc_tree_block+0x1e0/0x12c0 fs/btrfs/extent-tree.c:5114
  btrfs_force_cow_block+0x3e5/0x19e0 fs/btrfs/ctree.c:563
  btrfs_cow_block+0x2b6/0xb30 fs/btrfs/ctree.c:741
  push_leaf_left+0x315/0x4d0 fs/btrfs/ctree.c:3485
  split_leaf+0x9c3/0x13b0 fs/btrfs/ctree.c:3681
  search_leaf fs/btrfs/ctree.c:1944 [inline]
  btrfs_search_slot+0x24ba/0x2fd0 fs/btrfs/ctree.c:2131
  btrfs_insert_empty_items+0xb6/0x1b0 fs/btrfs/ctree.c:4285
  btrfs_insert_empty_item fs/btrfs/ctree.h:657 [inline]
  insert_reserved_file_extent+0x7aa/0x950 fs/btrfs/inode.c:2907
  insert_ordered_extent_file_extent fs/btrfs/inode.c:3005 [inline]
  btrfs_finish_one_ordered+0x12dc/0x20d0 fs/btrfs/inode.c:3113
  btrfs_work_helper+0x210/0xbf0 fs/btrfs/async-thread.c:315
  process_one_work+0x886/0x15d0 kernel/workqueue.c:2630
  process_scheduled_works kernel/workqueue.c:2703 [inline]
  worker_thread+0x8b9/0x1290 kernel/workqueue.c:2784
  kthread+0x2c6/0x3a0 kernel/kthread.c:388
  ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
-----------------

btrfs_use_block_rsv()
<snap>
         /*
          * The global reserve still exists to save us from ourselves, 
so don't
          * warn_on if we are short on our delayed refs reserve.
          */
         if (block_rsv->type != BTRFS_BLOCK_RSV_DELREFS &&
             btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
                 static DEFINE_RATELIMIT_STATE(_rs,
                                 DEFAULT_RATELIMIT_INTERVAL * 10,
                                 /*DEFAULT_RATELIMIT_BURST*/ 1);
                 if (__ratelimit(&_rs))
                         WARN(1, KERN_DEBUG
                                 "BTRFS: block rsv %d returned %d\n",
                                 block_rsv->type, ret);
         }
----------


Thanks, Anand