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

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

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@xxxxxxxxxx>
> >
> > Avoid to access bd_inode directly, prepare to remove bd_inode from
> > block_device.
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> 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