Re: [PATCHv4 9/9] fs: add support for dma aligned direct-io

Damien Le Moal
2022-05-26T02:01:25Z

On 2022/05/26 10:06, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
>
> Use the address alignment requirements from the hardware for direct io
> instead of requiring addresses be aligned to the block size.
>
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
> fs/direct-io.c | 11 +++++++----
> fs/iomap/direct-io.c | 3 ++-
> 2 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 840752006f60..64cc176be60c 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -1131,7 +1131,7 @@ ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
> struct dio_submit sdio = { 0, };
> struct buffer_head map_bh = { 0, };
> struct blk_plug plug;
> - unsigned long align = offset | iov_iter_alignment(iter);
> + unsigned long align = iov_iter_alignment(iter);
>
> /*
> * Avoid references to bdev if not absolutely needed to give
> @@ -1165,11 +1165,14 @@ ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
> goto fail_dio;
> }
>
> - if (align & blocksize_mask) {
> - if (bdev)
> + if ((offset | align) & blocksize_mask) {
> + if (bdev) {
> blkbits = blksize_bits(bdev_logical_block_size(bdev));
> + if (align & bdev_dma_alignment(bdev))
> + goto fail_dio;
> + }
> blocksize_mask = (1 << blkbits) - 1;
> - if (align & blocksize_mask)
> + if ((offset | count) & blocksize_mask)
> goto fail_dio;
> }
>
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 80f9b047aa1b..0256d28baa8e 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -244,7 +244,8 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
> size_t copied = 0;
> size_t orig_count;
>
> - if ((pos | length | align) & ((1 << blkbits) - 1))
> + if ((pos | length) & ((1 << blkbits) - 1) ||
> + align & bdev_dma_alignment(iomap->bdev))
> return -EINVAL;
>
> if (iomap->type == IOMAP_UNWRITTEN) {

Looks good to me.

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

--
Damien Le Moal
Western Digital Research