Re: WARNING in btrfs_run_delayed_refs

[Qu Wenruo]

On 2021/9/15 上午10:56, Hao Sun wrote:
> Qu Wenruo <quwenruo.btrfs@xxxxxxx> 于2021年9月15日周三 上午10:20写道：
> > On 2021/9/15 上午10:14, Hao Sun wrote:
> > > Hello,
> > >
> > > When using Healer to fuzz the latest Linux kernel, the following crash
> > > was triggered.
> > >
> > > HEAD commit: 6880fa6c5660 Linux 5.15-rc1
> > > git tree: upstream
> > > console output:
> > > https://drive.google.com/file/d/1gd0dl74MyvvVAYqsCDKSGmcfpZszD0kt/view?usp=sharing
> > > kernel config: https://drive.google.com/file/d/1rUzyMbe5vcs6khA3tL9EHTLJvsUdWcgB/view?usp=sharing
> > > C reproducer: https://drive.google.com/file/d/1WKQukijOJ7D0NYk1iKf47FESjYfAjrlz/view?usp=sharing
> > > Syzlang reproducer:
> > > https://drive.google.com/file/d/1Gi9-Mgbrjw1OI-ymO4zDVIFej2Qf4ppL/view?usp=sharing
> > >
> > > If you fix this issue, please add the following tag to the commit:
> > > Reported-by: Hao Sun <sunhao.th@xxxxxxxxx>
> > >
> > > loop11: detected capacity change from 0 to 32768
> > > BTRFS info (device loop11): disk space caching is enabled
> > > BTRFS info (device loop11): has skinny extents
> > > BTRFS info (device loop11): enabling ssd optimizations
> > > FAULT_INJECTION: forcing a failure.
> > > name failslab, interval 1, probability 0, space 0, times 0
> > > CPU: 0 PID: 7769 Comm: syz-executor Not tainted 5.15.0-rc1 #16
> > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > > rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> > > Call Trace:
> > >    __dump_stack lib/dump_stack.c:88 [inline]
> > >    dump_stack_lvl+0x8d/0xcf lib/dump_stack.c:106
> > >    fail_dump lib/fault-inject.c:52 [inline]
> > >    should_fail+0x13c/0x160 lib/fault-inject.c:146
> > >    should_failslab+0x5/0x10 mm/slab_common.c:1328
> > >    slab_pre_alloc_hook.constprop.99+0x4e/0xc0 mm/slab.h:494
> > >    slab_alloc_node mm/slub.c:3120 [inline]
> > >    slab_alloc mm/slub.c:3214 [inline]
> > >    kmem_cache_alloc+0x44/0x280 mm/slub.c:3219
> > >    __btrfs_free_extent.isra.53+0x7b/0x1180 fs/btrfs/extent-tree.c:2942
> > >    run_delayed_tree_ref fs/btrfs/extent-tree.c:1687 [inline]
> > >    run_one_delayed_ref fs/btrfs/extent-tree.c:1711 [inline]
> > >    btrfs_run_delayed_refs_for_head fs/btrfs/extent-tree.c:1952 [inline]
> > >    __btrfs_run_delayed_refs+0x83e/0x1a00 fs/btrfs/extent-tree.c:2017
> > >    btrfs_run_delayed_refs+0xb1/0x2b0 fs/btrfs/extent-tree.c:2148
> > >    btrfs_commit_transaction+0x7d/0x1430 fs/btrfs/transaction.c:2065
> > >    btrfs_sync_fs+0x9a/0x430 fs/btrfs/super.c:1426
> > >    btrfs_ioctl+0x209b/0x3be0 fs/btrfs/ioctl.c:4970
> > >    vfs_ioctl fs/ioctl.c:51 [inline]
> > >    __do_sys_ioctl fs/ioctl.c:874 [inline]
> > >    __se_sys_ioctl fs/ioctl.c:860 [inline]
> > >    __x64_sys_ioctl+0xb6/0x100 fs/ioctl.c:860
> > >    do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > >    do_syscall_64+0x34/0xb0 arch/x86/entry/common.c:80
> > >    entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > RIP: 0033:0x46ae99
> > > Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 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 bc ff ff ff f7 d8 64 89 01 48
> > > RSP: 002b:00007f8ac08c7c48 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > > RAX: ffffffffffffffda RBX: 000000000078c0a0 RCX: 000000000046ae99
> > > RDX: 0000000000000000 RSI: 0000000000009408 RDI: 0000000000000003
> > > RBP: 00007f8ac08c7c80 R08: 0000000000000000 R09: 0000000000000000
> > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
> > > R13: 0000000000000000 R14: 000000000078c0a0 R15: 00007ffccc1d6390
> > > ------------[ cut here ]------------
> > > WARNING: CPU: 0 PID: 7769 at fs/btrfs/extent-tree.c:2150
> > > btrfs_run_delayed_refs+0x245/0x2b0 fs/btrfs/extent-tree.c:2150
> >
> > This is again btrfs_abort_transaction().
> >
> > This makes me wonder, should we add ENOMEM to abort transaction warning
> > condition to make the ENOMEM injection code happy.
> >
> > Mind to test the following diff?
> >
> > Thanks,
> > Qu
> >
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index 8c6ee947a68d..6bc79f6716fa 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -3548,7 +3548,8 @@ do {
> >                   \
> >           /* Report first abort since mount */                    \
> >           if (!test_and_set_bit(BTRFS_FS_STATE_TRANS_ABORTED,     \
> >                           &((trans)->fs_info->fs_state))) {       \
> > -               if ((errno) != -EIO && (errno) != -EROFS) {             \
> > +               if ((errno) != -EIO && (errno) != -EROFS &&     \
> > +                   (errno) != -ENOMEM) {                       \
> >                           WARN(1, KERN_DEBUG                              \
> >                           "BTRFS: Transaction aborted (error %d)\n",      \
> >                           (errno));                                       \
>
> Just tested it. This did fixed most `WARNING` reports, e.g., "WARNING
> in btrfs_add_link", "WARNING in btrfs_run_delayed_refs".
> I think it would be better if we can judge whether the  `ENOMEM` is
> caused by `fault injection` or not.
This is really hard to distinguish.

If the fuzzer test tool can do it by relating the transaction abort
message with error injection log, it would save us a lot of time and
prevent false alerts.

For now, I guess the above diff would be a quick and dirty filter for
ENOMEM injection tests.

Thanks,
Qu