[syzbot] [btrfs?] WARNING in btrfs_use_block_rsv

[syzbot] [btrfs?] WARNING in btrfs_use_block_rsv

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    3b35375f19fe Merge tag 'irq-urgent-2023-08-26' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1156791fa80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=67db137b0441ab96
dashboard link: https://syzkaller.appspot.com/bug?extid=10d5b62a8d7046b86d22
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1767c1e0680000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=146903b0680000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-3b35375f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/34c4f640b690/vmlinux-3b35375f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/58c9c2459f41/bzImage-3b35375f.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/501d7ead33fe/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+10d5b62a8d7046b86d22@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 5212 at fs/btrfs/block-rsv.c:515 btrfs_use_block_rsv+0x688/0x7f0 fs/btrfs/block-rsv.c:515
Modules linked in:
CPU: 1 PID: 5212 Comm: kworker/u17:1 Not tainted 6.5.0-rc7-syzkaller-00182-g3b35375f19fe #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: btrfs-endio-write btrfs_work_helper
RIP: 0010:btrfs_use_block_rsv+0x688/0x7f0 fs/btrfs/block-rsv.c:515
Code: 89 ea 83 e2 07 38 d0 7f 0c 84 c0 74 08 48 89 ef e8 ed 42 47 fe 0f b6 73 5a ba e4 ff ff ff 48 c7 c7 00 e4 b7 8a e8 b8 b8 ba fd <0f> 0b e9 a3 fd ff ff e8 8c f7 f3 fd 49 8d 9d 80 04 00 00 e9 1c fb
RSP: 0018:ffffc90003737030 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff8880323ba608 RCX: 0000000000000000
RDX: ffff888029a1c4c0 RSI: ffffffff814be3c6 RDI: 0000000000000001
RBP: ffff8880323ba662 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 000000002d2d2d2d R12: 0000000000001000
R13: ffff88801fb84000 R14: 0000000000000001 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88806b700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020d41000 CR3: 00000000219e2000 CR4: 0000000000350ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 btrfs_alloc_tree_block+0x1dd/0x1420 fs/btrfs/extent-tree.c:4883
 __btrfs_cow_block+0x3ce/0x18e0 fs/btrfs/ctree.c:546
 btrfs_cow_block+0x2f1/0x820 fs/btrfs/ctree.c:712
 btrfs_search_slot+0x12a0/0x30e0 fs/btrfs/ctree.c:2194
 btrfs_lookup_file_extent+0xcb/0x110 fs/btrfs/file-item.c:270
 btrfs_drop_extents+0x433/0x2bd0 fs/btrfs/file.c:250
 insert_reserved_file_extent+0x3a8/0x940 fs/btrfs/inode.c:3057
 insert_ordered_extent_file_extent fs/btrfs/inode.c:3164 [inline]
 btrfs_finish_one_ordered+0x1443/0x2240 fs/btrfs/inode.c:3268
 btrfs_work_helper+0x20b/0xba0 fs/btrfs/async-thread.c:314
 process_one_work+0xaa2/0x16f0 kernel/workqueue.c:2600
 worker_thread+0x687/0x1110 kernel/workqueue.c:2751
 kthread+0x33a/0x430 kernel/kthread.c:389
 ret_from_fork+0x2c/0x70 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this issue. See:
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If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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If you want to overwrite bug's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

Re: [syzbot] [btrfs?] WARNING in btrfs_use_block_rsv

[syzbot]

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

Re: [syzbot] [btrfs?] WARNING in btrfs_use_block_rsv

[Anand Jain]

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

Re: [syzbot] [btrfs?] WARNING in btrfs_use_block_rsv

[David Sterba]

On Sun, Nov 26, 2023 at 06:59:41AM +0800, Anand Jain wrote:
> 
> 
> 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.

I think it's because of changed timing or it can be an inconclusive
bisect. Things around space handling depend on timing, the test would
need to be run a few times to be sure.

The report provides an image so it may be good to analyze if it's scaled
properly or if the reproducer does something strange.

> -------------------
> 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);
>          }
> ----------

Re: [syzbot] [btrfs?] WARNING in btrfs_use_block_rsv

[Aleksandr Nogikh]

On Tue, Nov 28, 2023 at 5:47 PM David Sterba <dsterba@suse.cz> wrote:
>
> On Sun, Nov 26, 2023 at 06:59:41AM +0800, Anand Jain wrote:
> >
> >
> > 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.
>
> I think it's because of changed timing or it can be an inconclusive
> bisect. Things around space handling depend on timing, the test would
> need to be run a few times to be sure.
>
> The report provides an image so it may be good to analyze if it's scaled
> properly or if the reproducer does something strange.

Bisection log itself looks reasonable.

One other case to consider is that "btrfs: support cloned-device mount
capability" just helped surface the problem. Syzbot can only bisect
for the revision at which the reproducer started/stopped working and,
even though we try to minimize the reproducer (*), it may still rely
on some functionality that's not related to the actual bug. One of the
possibilities here is that the slightly changed validation rules in
btrfs_validate_super() allowed syzkaller to trigger a problem
somewhere else.

(*) We don't do it for filesystem images themselves as it does not
make very much sense -- in almost all cases by zeroing/dropping bytes
syzkaller just breaks the image and the reproducer stops working.
Without knowing the underlying fs image structure in detail it just
doesn't work as intended.

-- 
Aleksandr
>
> > -------------------
> > 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);
> >          }
> > ----------
>
> --
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