Re: [PATCH 1/3] f2fs: avoid calling i_size_read when it's unnecessary

[Jaegeuk Kim <jaegeuk@kernel.org>]

Hi Fan,

On Wed, Dec 30, 2015 at 04:49:56PM +0800, Fan Li wrote:
> i_size_read does more than reading a value, it's best that we use it
> only when we need it.
> 
> Signed-off-by: Fan li <fanofcode.li@samsung.com>
> ---
>  fs/f2fs/data.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index d67c599..a9a4d89 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -780,7 +780,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  {
>  	struct buffer_head map_bh;
>  	sector_t start_blk, last_blk;
> -	loff_t isize = i_size_read(inode);
> +	loff_t isize;
>  	u64 logical = 0, phys = 0, size = 0;
>  	u32 flags = 0;
>  	int ret = 0;
> @@ -795,6 +795,8 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  			return ret;
>  	}
>  
> +	isize = i_size_read(inode);

It seems that we need to get isize after grabbing i_mutex below in order to
avoid data race.

Thanks,

> +
>  	mutex_lock(&inode->i_mutex);
>  	if (start >= isize)
>  		goto out;
> -- 
> 1.7.9.5
> 

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