linux-kernel - Re: [syzbot] [ext4?] INFO: task hung in ext4_evict_ea

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Message-ID: <da2d3fb8-b4b0-457a-80fa-a3eae5c8e1fc@acm.org>
Date: Mon, 16 Sep 2024 06:41:00 -0700
From: Bart Van Assche <bvanassche@....org>
To: Dmitry Vyukov <dvyukov@...gle.com>
Cc: syzbot <syzbot+38e6635a03c83c76297a@...kaller.appspotmail.com>,
 adilger.kernel@...ger.ca, alim.akhtar@...sung.com, avri.altman@....com,
 beanhuo@...ron.com, hdanton@...a.com, jejb@...ux.ibm.com,
 linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-scsi@...r.kernel.org, martin.petersen@...cle.com,
 syzkaller-bugs@...glegroups.com, tytso@....edu,
 wsa+renesas@...g-engineering.com, syzkaller <syzkaller@...glegroups.com>
Subject: Re: [syzbot] [ext4?] INFO: task hung in ext4_evict_ea_inode

On 9/16/24 6:28 AM, Dmitry Vyukov wrote:
> On Fri, 3 Feb 2023 at 19:11, Bart Van Assche <bvanassche@....org> wrote:
>>
>> On 2/3/23 00:53, syzbot wrote:
>>> syzbot has bisected this issue to:
>>>
>>> commit 82ede9c19839079e7953a47895729852a440080c
>>> Author: Wolfram Sang <wsa+renesas@...g-engineering.com>
>>> Date:   Tue Jun 21 14:46:53 2022 +0000
>>>
>>>       scsi: ufs: core: Fix typos in error messages
>>
>> To the syzbot maintainers: I think this is a good example of a bisection
>> result that is wrong. It is unlikely that fixing typos in kernel
>> messages would affect whether or not the kernel hangs. Additionally, as
>> far as I know, the systems used by syzbot (Google Compute Engine virtual
>> machines) do trigger any code in the UFS driver.
> 
> Hi Bart,
> 
> syzbot has logic to detect commits that don't affect builds.
> It hashes SHF_ALLOC vmlinux sections to check if the commit actually
> has any effect on the binary:
> https://github.com/google/syzkaller/blob/c673ca06b23cea94091ab496ef62c3513e434585/pkg/build/linux.go#L253-L286
> 
> Bug CONFIG_UFS_FS is enabled on syzbot, it has some coverage for it,
> and strings affect the binary (can actually be the root cause for
> bugs). So I don't see what else can be done here automatically.

CONFIG_UFS_FS controls whether or not the UFS filesystem is enabled
(fs/ufs/). The UFS driver is unrelated to the UFS filesystem and is
controlled by CONFIG_SCSI_UFSHCD. Support for the UFS driver has been
added recently in Qemu. Does that mean that it should be possible to
test the UFS driver with syzbot? See also
https://patchew.org/QEMU/20230616065816epcms2p82787f1aeb410ec4b8ab6ffedb6edf4d2@epcms2p8/

Thanks,

Bart.