On Tue, 2025-07-08 at 12:06 -0400, Mike Snitzer wrote:
> iov_iter_aligned_bvec() is strictly checking alignment of each element
> of the bvec to arrive at whether the bvec is aligned relative to
> dma_alignment and on-disk alignment. Checking each element
> individually results in disallowing a bvec that in aggregate is
> perfectly aligned relative to the provided @len_mask.
>
> Relax the on-disk alignment checking such that it is done on the full
> extent described by the bvec but still do piecewise checking of the
> dma_alignment for each bvec's bv_offset.
>
> This allows for NFS's WRITE payload to be issued using O_DIRECT as
> long as the bvec created with xdr_buf_to_bvec() is composed of pages
> that respect the underlying device's dma_alignment (@addr_mask) and
> the overall contiguous on-disk extent is aligned relative to the
> logical_block_size (@len_mask).
>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> lib/iov_iter.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index bdb37d572e97..b2ae482b8a1d 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -819,13 +819,14 @@ static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
> unsigned skip = i->iov_offset;
> size_t size = i->count;
>
> + if (size & len_mask)
> + return false;
> +
> do {
> size_t len = bvec->bv_len;
>
> if (len > size)
> len = size;
> - if (len & len_mask)
> - return false;
> if ((unsigned long)(bvec->bv_offset + skip) & addr_mask)
> return false;
>
cc'ing Keith too since he wrote this helper originally. Should this
also get a:
Fixes: cfa320f72882 ("iov: introduce iov_iter_aligned")
?
--
Jeff Layton <jlayton@xxxxxxxxxx>
