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Message-ID: <1812c1bf-08b5-46a5-a633-12470e2c8f18@linux.alibaba.com>
Date:   Tue, 12 Dec 2023 14:35:51 +0800
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Subject: Re: [PATCH RFC v2 for-6.8/block 11/18] erofs: use bdev api
To:     Yu Kuai <yukuai1@huaweicloud.com>, 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,
        agruenba@redhat.com, jack@suse.com, konishi.ryusuke@gmail.com,
        willy@infradead.org, akpm@linux-foundation.org,
        p.raghav@samsung.com, hare@suse.de
Cc:     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,
        gfs2@lists.linux.dev, linux-nilfs@vger.kernel.org,
        yukuai3@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com
References: <20231211140552.973290-1-yukuai1@huaweicloud.com>
 <20231211140722.974745-1-yukuai1@huaweicloud.com>
From:   Gao Xiang <hsiangkao@linux.alibaba.com>
In-Reply-To: <20231211140722.974745-1-yukuai1@huaweicloud.com>
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On 2023/12/11 22:07, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> Avoid to access bd_inode directly, prepare to remove bd_inode from
> block_devcie.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
>   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..8cf3618190ab 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -32,8 +32,7 @@ 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;
> +	erofs_off_t offset = (erofs_off_t)blkaddr << buf->blkszbits;
I'd suggest that use `buf->blkszbits` only for bdev_read_folio() since
erofs_init_metabuf() is not always called before erofs_bread() is used.

For example, buf->inode can be one of directory inodes other than
initialized by erofs_init_metabuf().

Thanks,
Gao Xiang


>   	pgoff_t index = offset >> PAGE_SHIFT;
>   	struct page *page = buf->page;
>   	struct folio *folio;
> @@ -43,7 +42,9 @@ 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 +68,15 @@ 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;
> +		buf->blkszbits = buf->inode->i_blkbits;
> +	} 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 })