linux-kernel - Re: [GIT PULL] erofs fix for 6.19-rc5 (fix the stupid mistake)

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Message-ID: <fba595da-9bd9-42c6-8b1d-1511feafda14@linux.alibaba.com>
Date: Sat, 10 Jan 2026 19:54:29 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Amir Goldstein <amir73il@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
 linux-erofs@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>,
 Alexander Larsson <alexl@...hat.com>, Dusty Mabe <dusty@...tymabe.com>,
 Chao Yu <chao@...nel.org>, Sheng Yong <shengyong1@...omi.com>,
 Zhiguo Niu <zhiguo.niu@...soc.com>, Christian Brauner <brauner@...nel.org>,
 Miklos Szeredi <mszeredi@...hat.com>, Gao Xiang <xiang@...nel.org>
Subject: Re: [GIT PULL] erofs fix for 6.19-rc5 (fix the stupid mistake)



On 2026/1/10 18:48, Amir Goldstein wrote:
> On Sat, Jan 10, 2026 at 11:30 AM Gao Xiang <hsiangkao@...ux.alibaba.com> wrote:
>>
>> Hi Amir,
>>
>> On 2026/1/10 17:50, Amir Goldstein wrote:
>>> On Sat, Jan 10, 2026 at 8:27 AM Gao Xiang <xiang@...nel.org> wrote:
>>>>
>>>> Hi Linus,
>>>>
>>>> Very sorry I sent an incorrect pull request which used an
>>>> outdated PATCH version (I just manually applied tags on the
>>>> incorrect version, but I didn't realize), I shouldn't make
>>>> the stupid mistake in the beginning.
>>>>
>>>> Someone reminded me the mistake just now.
>>>>
>>>> Could you please apply this pull request, I promise that I
>>>> won't make the similar fault again and I should be blamed.
>>>>
>>>> Thanks,
>>>> Gao Xiang
>>>>
>>>> The following changes since commit 072a7c7cdbea4f91df854ee2bb216256cd619f2a:
>>>>
>>>>     erofs: don't bother with s_stack_depth increasing for now (2026-01-10 13:01:15 +0800)
>>>>
>>>> are available in the Git repository at:
>>>>
>>>>     git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git tags/erofs-for-6.19-rc5-fixes-2
>>>>
>>>> for you to fetch changes up to 0a7468a8de7a2721cc0cce30836726f2a3ac2120:
>>>>
>>>>     erofs: don't bother with s_stack_depth increasing for now [real fix] (2026-01-10 15:13:12 +0800)
>>>>
>>>> ----------------------------------------------------------------
>>>> Changes since last update:
>>>>
>>>>    - Revert the incorrect outdated PATCH version
>>>>
>>>>    - Apply the correct fix of
>>>>      "erofs: don't bother with s_stack_depth increasing for now"
>>>>
>>>> ----------------------------------------------------------------
>>>> Gao Xiang (2):
>>>>         Revert "erofs: don't bother with s_stack_depth increasing for now"
>>>>         erofs: don't bother with s_stack_depth increasing for now [real fix]
>>>>
>>>
>>> Gao,
>>>
>>> You merged the wrong patch version by mistake - no real harm done.
>>
>> Sadly, the merged one doesn't work for Android APEX (Sheng actually
>> claimed that PATCH v3 RESEND works instead of PATCH v3 [I'm very sorry
>> for v3 RESEND mark again here] and it was him found that the merged
>> pull request used wrong version and he gave me a private text hours
>> ago), see my explanation below.
>>
> 
> Yes. That's what I said.
> 
>>>
>>> But now that it was merged, for the sake of git history, I think it would
>>> be better to merge a fix patch rather than revert + patch with same title.
>>
>> My concern would be that people could merge incomplete patch chain,
>> but I'm fine to send a fix for the fix, I will do.
>>
> 
> This is what the Fixes: tag is for.
> Stable kernel maintainers know how to look for those when applying fixes.

For stable kernels, Yes.

But there could be customized downstream kernels, yet I totally
agree with you, "revert + patch with same title" won't be better
in any aspect.

> 
>>>
>>> If you merge a fix patch you could properly attribute Report/Review/Tested-by
>>> to Sheng Yong [1].
>>>
>>> It's true that the merged patch already claims to work for Android APEX,
>>> but it had a braino bug and this is what fix patches are for.
>>
>> Sigh, the merged patch (PATCH v3) actually _breaks_ APEX (it's just
>> like PATCH v1/v2), because:
>>                  if (erofs_is_fileio_mode(sbi)) {
>> -                       sb->s_stack_depth =
>> -                               file_inode(sbi->dif0.file)->i_sb->s_stack_depth + 1;
>> -                       if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
>> -                               erofs_err(sb, "maximum fs stacking depth exceeded");
>> +                       inode = file_inode(sbi->dif0.file);
>> +                       if ((inode->i_sb->s_op == &erofs_sops && !sb->s_bdev) ||
>>
>> Here `!sb->s_bdev` is true for all file-backed mounts all the time,
>> so `!sb->s_bdev` equals to a no-op.
>>
>> +                           inode->i_sb->s_stack_depth) {
>>
>> I will make a delta patch candidate with his "Reported-by:" and
>> "Tested-by:", I will try to send now.
>>
>> It seems I need to sleep later because my brain is exhaused,
>> and always screwed things up, very very sorry about that.
>>
> 
> Mistakes happen.
> This is built into the process.
> This will not be the first time that a fix patch is also a regression.
> Sometimes its detected on the same day and sometimes weeks later...

I've sent out a delta fix:
https://lore.kernel.org/r/20260110114703.3461706-1-hsiangkao@linux.alibaba.com

Hopefully it's the end of the disaster.

Thanks,
Gao Xiang

> 
> Thanks,
> Amir.