Re: [PATCH v2 2/3] direct-io: don't force writeback for reads beyond EOF

[Jan Kara <jack@suse.cz>]

On Thu 03-09-20 16:04:13, Gabriel Krisman Bertazi wrote:
> If a DIO read starts past EOF, the kernel won't attempt it, so we don't
> need to flush dirty pages before failing the syscall.
> 
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

This patch looks good to me. You can add:

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

								Honza

> ---
>  fs/direct-io.c | 24 +++++++++++-------------
>  1 file changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 04aae41323d7..43460c8e0f90 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -1188,19 +1188,9 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
>  	memset(dio, 0, offsetof(struct dio, pages));
>  
>  	dio->flags = flags;
> -	if (dio->flags & DIO_LOCKING) {
> -		if (iov_iter_rw(iter) == READ) {
> -			struct address_space *mapping =
> -					iocb->ki_filp->f_mapping;
> -
> -			/* will be released by direct_io_worker */
> -			inode_lock(inode);
> -
> -			retval = filemap_write_and_wait_range(mapping, offset,
> -							      end - 1);
> -			if (retval)
> -				goto fail_dio;
> -		}
> +	if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {
> +		/* will be released by direct_io_worker */
> +		inode_lock(inode);
>  	}
>  
>  	/* Once we sampled i_size check for reads beyond EOF */
> @@ -1210,6 +1200,14 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
>  		goto fail_dio;
>  	}
>  
> +	if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {
> +		struct address_space *mapping = iocb->ki_filp->f_mapping;
> +
> +		retval = filemap_write_and_wait_range(mapping, offset, end - 1);
> +		if (retval)
> +			goto fail_dio;
> +	}
> +
>  	/*
>  	 * For file extending writes updating i_size before data writeouts
>  	 * complete can expose uninitialized blocks in dumb filesystems.
> -- 
> 2.28.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR