linux-ext4 - Re: [PATCH RFC v3 for-6.8/block 11/17] erofs: use bdev api

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Date: Thu, 4 Jan 2024 20:32:43 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Jan Kara <jack@...e.cz>, Yu Kuai <yukuai1@...weicloud.com>
Cc: axboe@...nel.dk, roger.pau@...rix.com, colyli@...e.de,
 kent.overstreet@...il.com, joern@...ybastard.org, miquel.raynal@...tlin.com,
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 linux-fsdevel@...r.kernel.org, linux-erofs@...ts.ozlabs.org,
 linux-ext4@...r.kernel.org, linux-nilfs@...r.kernel.org,
 yi.zhang@...wei.com, yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH RFC v3 for-6.8/block 11/17] erofs: use bdev api

Hi, Jan!

在 2024/01/04 20:02, Jan Kara 写道:
> On Thu 21-12-23 16:58:26, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> Avoid to access bd_inode directly, prepare to remove bd_inode from
>> block_device.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.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
>>