Re: [RFC PATCH 3/8] fat: add iomap direct I/O support

[OGAWA Hirofumi]

Matheus Alves de Almeida <matheus.aalmeida@xxxxxxxxxxxx> writes:

> Replace the deprecated ->direct_IO() path with ->{read,write}_iter() and
> iomap_dio_rw(). Add fat_file_open() to advertise direct I/O support.
>
> Signed-off-by: Matheus Alves de Almeida <matheus.aalmeida@xxxxxxxxxxxx>
> ---
>  fs/fat/Kconfig |   1 -
>  fs/fat/fat.h   |   1 +
>  fs/fat/file.c  | 119 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  fs/fat/inode.c |  36 ---------------
>  fs/fat/iomap.c |  24 ++++++++++
>  5 files changed, 142 insertions(+), 39 deletions(-)
>

[...]

> diff --git a/fs/fat/file.c b/fs/fat/file.c
> index c27d4e7f698c..177a26186ddc 100644
> --- a/fs/fat/file.c
> +++ b/fs/fat/file.c
> @@ -201,11 +201,126 @@ int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
>  	return blkdev_issue_flush(inode->i_sb->s_bdev);
>  }
>  

[...]

> +static ssize_t fat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
> +{
> +	ssize_t ret;
> +
> +	if ((iocb->ki_flags & IOCB_DIRECT) == 0)
> +		return generic_file_write_iter(iocb, iter);
> +
> +	ret = fat_file_dio_write_iter(iocb, iter);
> +	if (ret == -ENOTBLK)
> +		ret = 0;
> +	else if (ret < 0)
> +		return ret;
> +
> +	/* Fall back to buffered I/O if we could not do DIO */
> +	if (iov_iter_count(iter)) {
> +		ssize_t done;
> +
> +		done = fat_file_write_iter_buffered_fallback(iocb, iter);
> +		if (done < 0)
> +			return done;

If fat_file_dio_write_iter() wrote some, this should return ret (how
many written), instead of the error? Or it never happen?

> +		ret += done;
> +	}
> +
> +	return ret;
> +}

Thanks.
-- 
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>