Received-SPF: pass (google.com: domain of linux-ext4+bounces-688-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Subject: Re: [PATCH RFC v3 for-6.8/block 11/17] erofs: use bdev api
To: Jan Kara <jack@suse.cz>, Yu Kuai <yukuai1@huaweicloud.com>
Cc: axboe@kernel.dk, roger.pau@citrix.com, colyli@suse.de,
 kent.overstreet@gmail.com, joern@lazybastard.org, miquel.raynal@bootlin.com,
 richard@nod.at, vigneshr@ti.com, sth@linux.ibm.com, hoeppner@linux.ibm.com,
 hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com,
 jejb@linux.ibm.com, martin.petersen@oracle.com, clm@fb.com,
 josef@toxicpanda.com, dsterba@suse.com, viro@zeniv.linux.org.uk,
 brauner@kernel.org, nico@fluxnic.net, xiang@kernel.org, chao@kernel.org,
 tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.com,
 konishi.ryusuke@gmail.com, willy@infradead.org, akpm@linux-foundation.org,
 hare@suse.de, p.raghav@samsung.com, linux-block@vger.kernel.org,
 linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org,
 linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org,
 linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org,
 linux-bcachefs@vger.kernel.org, linux-btrfs@vger.kernel.org,
 linux-fsdevel@vger.kernel.org, linux-erofs@lists.ozlabs.org,
 linux-ext4@vger.kernel.org, linux-nilfs@vger.kernel.org,
 yi.zhang@huawei.com, yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
References: <20231221085712.1766333-1-yukuai1@huaweicloud.com>
 <20231221085826.1768395-1-yukuai1@huaweicloud.com>
 <20240104120207.ig7tfc3mgckwkp2n@quack3>
From: Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <7f868579-f993-aaa1-b7d7-eccbe0b0173c@huaweicloud.com>
Date: Thu, 4 Jan 2024 20:32:43 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101
 Thunderbird/60.8.0
Precedence: bulk
MIME-Version: 1.0
In-Reply-To: <20240104120207.ig7tfc3mgckwkp2n@quack3>
Content-Type: text/plain; charset=gbk; format=flowed
Content-Transfer-Encoding: 8bit

Hi, Jan!

?? 2024/01/04 20:02, Jan Kara д??:
> On Thu 21-12-23 16:58:26, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> Avoid to access bd_inode directly, prepare to remove bd_inode from
>> block_device.
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> 
> I'm not erofs maintainer but IMO this is quite ugly and grows erofs_buf
> unnecessarily. I'd rather store 'sb' pointer in erofs_buf and then do the
> right thing in erofs_bread() which is the only place that seems to care
> about the erofs_is_fscache_mode() distinction... Also blkszbits is then
> trivially sb->s_blocksize_bits so it would all seem much more
> straightforward.

Thanks for your suggestion, I'll follow this unless Gao Xiang has other
suggestions.

Kuai
> 
> 								Honza
> 
>> ---
>>   fs/erofs/data.c     | 18 ++++++++++++------
>>   fs/erofs/internal.h |  2 ++
>>   2 files changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
>> index c98aeda8abb2..bbe2fe199bf3 100644
>> --- a/fs/erofs/data.c
>> +++ b/fs/erofs/data.c
>> @@ -32,8 +32,8 @@ void erofs_put_metabuf(struct erofs_buf *buf)
>>   void *erofs_bread(struct erofs_buf *buf, erofs_blk_t blkaddr,
>>   		  enum erofs_kmap_type type)
>>   {
>> -	struct inode *inode = buf->inode;
>> -	erofs_off_t offset = (erofs_off_t)blkaddr << inode->i_blkbits;
>> +	u8 blkszbits = buf->inode ? buf->inode->i_blkbits : buf->blkszbits;
>> +	erofs_off_t offset = (erofs_off_t)blkaddr << blkszbits;
>>   	pgoff_t index = offset >> PAGE_SHIFT;
>>   	struct page *page = buf->page;
>>   	struct folio *folio;
>> @@ -43,7 +43,9 @@ void *erofs_bread(struct erofs_buf *buf, erofs_blk_t blkaddr,
>>   		erofs_put_metabuf(buf);
>>   
>>   		nofs_flag = memalloc_nofs_save();
>> -		folio = read_cache_folio(inode->i_mapping, index, NULL, NULL);
>> +		folio = buf->inode ?
>> +			read_mapping_folio(buf->inode->i_mapping, index, NULL) :
>> +			bdev_read_folio(buf->bdev, offset);
>>   		memalloc_nofs_restore(nofs_flag);
>>   		if (IS_ERR(folio))
>>   			return folio;
>> @@ -67,10 +69,14 @@ void *erofs_bread(struct erofs_buf *buf, erofs_blk_t blkaddr,
>>   
>>   void erofs_init_metabuf(struct erofs_buf *buf, struct super_block *sb)
>>   {
>> -	if (erofs_is_fscache_mode(sb))
>> +	if (erofs_is_fscache_mode(sb)) {
>>   		buf->inode = EROFS_SB(sb)->s_fscache->inode;
>> -	else
>> -		buf->inode = sb->s_bdev->bd_inode;
>> +		buf->bdev = NULL;
>> +	} else {
>> +		buf->inode = NULL;
>> +		buf->bdev = sb->s_bdev;
>> +		buf->blkszbits = EROFS_SB(sb)->blkszbits;
>> +	}
>>   }
>>   
>>   void *erofs_read_metabuf(struct erofs_buf *buf, struct super_block *sb,
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index b0409badb017..c9206351b485 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -224,8 +224,10 @@ enum erofs_kmap_type {
>>   
>>   struct erofs_buf {
>>   	struct inode *inode;
>> +	struct block_device *bdev;
>>   	struct page *page;
>>   	void *base;
>> +	u8 blkszbits;
>>   	enum erofs_kmap_type kmap_type;
>>   };
>>   #define __EROFS_BUF_INITIALIZER	((struct erofs_buf){ .page = NULL })
>> -- 
>> 2.39.2
>>