linux-kernel - Re: [PATCH v12 07/10] erofs: introduce the page cache share feature

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Message-ID: <48755c73-323d-469e-9125-07051daf7c19@huawei.com>
Date: Wed, 7 Jan 2026 15:32:53 +0800
From: Hongbo Li <lihongbo22@...wei.com>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>
CC: <djwong@...nel.org>, <amir73il@...il.com>, <hch@....de>,
	<linux-fsdevel@...r.kernel.org>, <linux-erofs@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>, Chao Yu <chao@...nel.org>,
	<brauner@...nel.org>
Subject: Re: [PATCH v12 07/10] erofs: introduce the page cache share feature



On 2026/1/7 15:27, Gao Xiang wrote:
> 
> 
> On 2026/1/7 15:17, Hongbo Li wrote:
>> Hi, Xiang
>>
> 
> ...
> 
>>>>>> +
>>>>>> +bool erofs_ishare_fill_inode(struct inode *inode)
>>>>>> +{
>>>>>> +    struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb);
>>>>>> +    struct erofs_inode *vi = EROFS_I(inode);
>>>>>> +    struct erofs_inode_fingerprint fp;
>>>>>> +    struct inode *sharedinode;
>>>>>> +    unsigned long hash;
>>>>>> +
>>>>>> +    if (!test_opt(&sbi->opt, INODE_SHARE))
>>>>>> +        return false;
>>>>>> +    (void)erofs_xattr_fill_ishare_fp(&fp, inode, sbi->domain_id);
>>>>>> +    if (!fp.size)
>>>>>> +        return false;
>>>>>
>>>>> Why not just:
>>>>>
>>>>>      if (erofs_xattr_fill_ishare_fp(&fp, inode, sbi->domain_id))
>>>>>          return false;
>>>>>
>>>>
>>>> When erofs_sb_has_ishare_xattrs returns false, 
>>>> erofs_xattr_fill_ishare_fp also considers success.
>>>
>>> Then why !test_opt(&sbi->opt, INODE_SHARE) didn't return?
>>>
>>
>> The MOUNT_INODE_SHARE flag is passed from user's mount option. And it 
>> is controllered by CONFIG_EROFS_FS_PAGE_CACHE_SHARE. I doesn't do the 
>> check when the superblock without ishare_xattrs. (It seems the mount 
>> options is static, although it is useless for mounting with 
>> inode_share on one EROFS image without ishare_xattrs).
>> So should we check that if the superblock has not ishare_xattrs 
>> feature, and we return -ENOSUPP?
> 
> I think you should just mask off the INODE_SHARE if the on-disk
> compat feature is unavailable, and print a warning just like
> FSDAX fallback.
> 

Ok, it seems reasonable, and also can remove the check logic in 
erofs_xattr_fill_ishare_fp. I will change in next version.

Thanks,
Hongbo

> Thanks,
> Gao Xiang