Re: [PATCH 2/2] file-posix: add statx(STATX_DIOALIGN) support

[Eric Biggers]

On Tue, Nov 01, 2022 at 03:00:31PM -0400, Stefan Hajnoczi wrote:
>      /* Let's try to use the logical blocksize for the alignment. */
> -    if (probe_logical_blocksize(fd, &bs->bl.request_alignment) < 0) {
> -        bs->bl.request_alignment = 0;
> +    if (!bs->bl.request_alignment) {
> +        if (probe_logical_blocksize(fd, &bs->bl.request_alignment) < 0) {
> +            bs->bl.request_alignment = 0;
> +        }
>      }
>  
>  #ifdef __linux__
> -    /*
> -     * The XFS ioctl definitions are shipped in extra packages that might
> -     * not always be available. Since we just need the XFS_IOC_DIOINFO ioctl
> -     * here, we simply use our own definition instead:
> -     */
> -    struct xfs_dioattr {
> -        uint32_t d_mem;
> -        uint32_t d_miniosz;
> -        uint32_t d_maxiosz;
> -    } da;
> -    if (ioctl(fd, _IOR('X', 30, struct xfs_dioattr), &da) >= 0) {
> -        bs->bl.request_alignment = da.d_miniosz;
> -        /* The kernel returns wrong information for d_mem */
> -        /* s->buf_align = da.d_mem; */
> +    if (!bs->bl.request_alignment) {

This patch changes the fallback code to make the request_alignment value from
probe_logical_blocksize() override the value from XFS_IOC_DIOINFO.  Is that
intentional?

> +        if (ioctl(fd, _IOR('X', 30, struct xfs_dioattr), &da) >= 0) {
> +            bs->bl.request_alignment = da.d_miniosz;
> +            /* The kernel returns wrong information for d_mem */
> +            /* s->buf_align = da.d_mem; */

Has this bug been reported to the XFS developers (linux-xfs@vger.kernel.org)?

- Eric