linux-kernel - Re: [PATCH 08/14] ocfs2: replace ll_rw

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Message-ID: <20220831113134.fdmklqore4uglz7g@quack3>
Date:   Wed, 31 Aug 2022 13:31:34 +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 08/14] ocfs2: replace ll_rw_block()

On Wed 31-08-22 15:21:05, Zhang Yi wrote:
> ll_rw_block() is not safe for the sync read path because it cannot
> guarantee that submitting read IO if the buffer has been locked. We
> could get false positive EIO after wait_on_buffer() if the buffer has
> been locked by others. So stop using ll_rw_block() in ocfs2.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
> ---
>  fs/ocfs2/aops.c  | 2 +-
>  fs/ocfs2/super.c | 5 +----
>  2 files changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index af4157f61927..1d65f6ef00ca 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -636,7 +636,7 @@ int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno,
>  			   !buffer_new(bh) &&
>  			   ocfs2_should_read_blk(inode, page, block_start) &&
>  			   (block_start < from || block_end > to)) {
> -			ll_rw_block(REQ_OP_READ, 1, &bh);
> +			bh_read_nowait(bh, 0);
>  			*wait_bh++=bh;
>  		}
>  
> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
> index e2cc9eec287c..4050f35bbd0c 100644
> --- a/fs/ocfs2/super.c
> +++ b/fs/ocfs2/super.c
> @@ -1763,10 +1763,7 @@ static int ocfs2_get_sector(struct super_block *sb,
>  	lock_buffer(*bh);
>  	if (!buffer_dirty(*bh))
>  		clear_buffer_uptodate(*bh);
> -	unlock_buffer(*bh);
> -	ll_rw_block(REQ_OP_READ, 1, bh);
> -	wait_on_buffer(*bh);
> -	if (!buffer_uptodate(*bh)) {
> +	if (bh_read_locked(*bh, 0)) {
>  		mlog_errno(-EIO);
>  		brelse(*bh);
>  		*bh = NULL;

I would just use bh_read() here and drop bh_read_locked() altogether...

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR