linux-kernel - Re: [PATCH] mm: adjust max read count in generic_file_buffered

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Message-ID: <20180719085812.sjup2odrjyuigt3l@quack2.suse.cz>
Date:   Thu, 19 Jul 2018 10:58:12 +0200
From:   Jan Kara <jack@...e.cz>
To:     Chengguang Xu <cgxu519@....com>
Cc:     akpm@...ux-foundation.org, jack@...e.cz,
        mgorman@...hsingularity.net, jlayton@...hat.com,
        ak@...ux.intel.com, mawilcox@...rosoft.com,
        tim.c.chen@...ux.intel.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Al Viro <viro@...IV.linux.org.uk>
Subject: Re: [PATCH] mm: adjust max read count in generic_file_buffered_read()

On Thu 19-07-18 16:17:26, Chengguang Xu wrote:
> When we try to truncate read count in generic_file_buffered_read(),
> should deliver (sb->s_maxbytes - offset) as maximum count not
> sb->s_maxbytes itself.
> 
> Signed-off-by: Chengguang Xu <cgxu519@....com>

Looks good to me. You can add:

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

BTW, I can see you didn't include two (I'd say the most important ;)
addresses to CC: Al Viro as a VFS maintainer and linux-fsdevel mailing
list. Although this code resides in mm/ it is in fact a filesystem code.
Added now.

								Honza

> ---
>  mm/filemap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 52517f28e6f4..5c2d481d21cf 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2064,7 +2064,7 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
>  
>  	if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
>  		return 0;
> -	iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
> +	iov_iter_truncate(iter, inode->i_sb->s_maxbytes - *ppos);
>  
>  	index = *ppos >> PAGE_SHIFT;
>  	prev_index = ra->prev_pos >> PAGE_SHIFT;
> -- 
> 2.17.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR