linux-ext4 - Re: [PATCH v2 03/14] fs/buffer: replace ll_rw

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Message-ID: <20220901154522.r37xszonxutm6bsk@quack3>
Date:   Thu, 1 Sep 2022 17:45:22 +0200
From:   Jan Kara <jack@...e.cz>
To:     Zhang Yi <yi.zhang@...wei.com>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, cluster-devel@...hat.com,
        ntfs3@...ts.linux.dev, ocfs2-devel@....oracle.com,
        reiserfs-devel@...r.kernel.org, jack@...e.cz, tytso@....edu,
        akpm@...ux-foundation.org, axboe@...nel.dk,
        viro@...iv.linux.org.uk, rpeterso@...hat.com, agruenba@...hat.com,
        almaz.alexandrovich@...agon-software.com, mark@...heh.com,
        dushistov@...l.ru, hch@...radead.org, chengzhihao1@...wei.com,
        yukuai3@...wei.com
Subject: Re: [PATCH v2 03/14] fs/buffer: replace ll_rw_block()

On Thu 01-09-22 21:34:54, Zhang Yi wrote:
> ll_rw_block() is not safe for the sync IO path because it skip buffers
> which has been locked by others, it could lead to false positive EIO
> when submitting read IO. So stop using ll_rw_block(), switch to use new
> helpers which could guarantee buffer locked and submit IO if needed.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/buffer.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/buffer.c b/fs/buffer.c
> index a6bc769e665d..aec568b3ae52 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -562,7 +562,7 @@ void write_boundary_block(struct block_device *bdev,
>  	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
>  	if (bh) {
>  		if (buffer_dirty(bh))
> -			ll_rw_block(REQ_OP_WRITE, 1, &bh);
> +			write_dirty_buffer(bh, 0);
>  		put_bh(bh);
>  	}
>  }
> @@ -1342,7 +1342,7 @@ void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
>  {
>  	struct buffer_head *bh = __getblk(bdev, block, size);
>  	if (likely(bh)) {
> -		ll_rw_block(REQ_OP_READ | REQ_RAHEAD, 1, &bh);
> +		bh_readahead(bh, REQ_RAHEAD);
>  		brelse(bh);
>  	}
>  }
> @@ -2022,7 +2022,7 @@ int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
>  		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
>  		    !buffer_unwritten(bh) &&
>  		     (block_start < from || block_end > to)) {
> -			ll_rw_block(REQ_OP_READ, 1, &bh);
> +			bh_read_nowait(bh, 0);
>  			*wait_bh++=bh;
>  		}
>  	}
> @@ -2582,11 +2582,9 @@ int block_truncate_page(struct address_space *mapping,
>  		set_buffer_uptodate(bh);
>  
>  	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
> -		err = -EIO;
> -		ll_rw_block(REQ_OP_READ, 1, &bh);
> -		wait_on_buffer(bh);
> +		err = bh_read(bh, 0);
>  		/* Uhhuh. Read error. Complain and punt. */
> -		if (!buffer_uptodate(bh))
> +		if (err < 0)
>  			goto unlock;
>  	}
>  
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR