Re: [PATCH 3/3] iomap: use filemap_range_needs_writeback() for O_DIRECT reads

[Jan Kara <jack@suse.cz>]

On Wed 24-02-21 09:44:55, Jens Axboe wrote:
> For reads, use the better variant of checking for the need to call
> filemap_write_and_wait_range() when doing O_DIRECT. This avoids falling
> back to the slow path for IOCB_NOWAIT, if there are no pages to wait for
> (or write out).
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>

Looks good to me. Feel free to add:

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

								Honza

> ---
>  fs/iomap/direct-io.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index e2c4991833b8..8c35a0041f0f 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -487,12 +487,28 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  		if (pos >= dio->i_size)
>  			goto out_free_dio;
>  
> +		if (iocb->ki_flags & IOCB_NOWAIT) {
> +			if (filemap_range_needs_writeback(mapping, pos, end)) {
> +				ret = -EAGAIN;
> +				goto out_free_dio;
> +			}
> +			iomap_flags |= IOMAP_NOWAIT;
> +		}
> +
>  		if (iter_is_iovec(iter))
>  			dio->flags |= IOMAP_DIO_DIRTY;
>  	} else {
>  		iomap_flags |= IOMAP_WRITE;
>  		dio->flags |= IOMAP_DIO_WRITE;
>  
> +		if (iocb->ki_flags & IOCB_NOWAIT) {
> +			if (filemap_range_has_page(mapping, pos, end)) {
> +				ret = -EAGAIN;
> +				goto out_free_dio;
> +			}
> +			iomap_flags |= IOMAP_NOWAIT;
> +		}
> +
>  		/* for data sync or sync, we need sync completion processing */
>  		if (iocb->ki_flags & IOCB_DSYNC)
>  			dio->flags |= IOMAP_DIO_NEED_SYNC;
> @@ -507,14 +523,6 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  			dio->flags |= IOMAP_DIO_WRITE_FUA;
>  	}
>  
> -	if (iocb->ki_flags & IOCB_NOWAIT) {
> -		if (filemap_range_has_page(mapping, pos, end)) {
> -			ret = -EAGAIN;
> -			goto out_free_dio;
> -		}
> -		iomap_flags |= IOMAP_NOWAIT;
> -	}
> -
>  	if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
>  		ret = -EAGAIN;
>  		if (pos >= dio->i_size || pos + count > dio->i_size)
> -- 
> 2.30.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR