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

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Message-ID: <9303721e-5b67-4c66-8369-61c5125b1fb1@linux.alibaba.com>
Date: Sat, 10 Jan 2026 18:30:01 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Amir Goldstein <amir73il@...il.com>,
 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)

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 outdated PATCH version (I just manually applied tags on the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   - Revert the incorrect outdated PATCH version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.

> 
> 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.

> 
> 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.

Thanks,
Gao Xiang

> 
> Thanks,
> Amir.
> 
> [1] https://lore.kernel.org/linux-fsdevel/243f57b8-246f-47e7-9fb1-27a771e8e9e8@gmail.com/