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

[Jan Kara <jack@xxxxxxx>]

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.

                                                                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
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR