linux-kernel - Re: [PATCH v2] erofs: fix file-backed mounts over FUSE

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Message-ID: <e878e14a-eec7-4df4-b33d-f2defa8a92cb@linux.alibaba.com>
Date: Fri, 15 Nov 2024 07:26:31 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: linux-erofs@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>,
 syzbot+0b1279812c46e48bb0c1@...kaller.appspotmail.com
Subject: Re: [PATCH v2] erofs: fix file-backed mounts over FUSE



On 2024/11/15 00:18, Al Viro wrote:
> On Thu, Nov 14, 2024 at 05:01:09PM +0800, Gao Xiang wrote:
>> --- a/fs/erofs/data.c
>> +++ b/fs/erofs/data.c
>> @@ -38,7 +38,9 @@ void *erofs_bread(struct erofs_buf *buf, erofs_off_t offset,
>>   	}
>>   	if (!folio || !folio_contains(folio, index)) {
>>   		erofs_put_metabuf(buf);
>> -		folio = read_mapping_folio(buf->mapping, index, NULL);
>> +		folio = buf->file ? read_mapping_folio(buf->file->f_mapping,
>> +					index, buf->file) :
>> +			read_mapping_folio(buf->mapping, index, NULL);
>>   		if (IS_ERR(folio))
>>   			return folio;
>>   	}
>> @@ -61,8 +63,8 @@ void erofs_init_metabuf(struct erofs_buf *buf, struct super_block *sb)
>>   {
>>   	struct erofs_sb_info *sbi = EROFS_SB(sb);
>>   
>> -	if (erofs_is_fileio_mode(sbi))
>> -		buf->mapping = file_inode(sbi->fdev)->i_mapping;
>> +	if (erofs_is_fileio_mode(sbi))	/* some fs like FUSE needs it */
>> +		buf->file = sbi->fdev;
> 
> Would be easier to set *both* ->mapping and ->file at that point, so that
> erofs_bread() would just have read_mapping_folio(buf->mapping, index, buf->file),
> unconditionally...

Ok, will do the next version.

Thanks,
Gao Xiang