Re: [PATCH 2/5] min_dio_alignment: add a -r option to query read alignment

[Christoph Hellwig <hch@lst.de>]

On Thu, Sep 03, 2026 at 12:26:26AM +0800, Zorro Lang wrote:
> On Mon, Aug 31, 2026 at 09:51:05AM +0300, Christoph Hellwig wrote:
> > Add an option to query the STATX_DIO_READ_ALIGN if provided.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  src/min_dio_alignment.c | 44 ++++++++++++++++++++++++++++++-----------
> >  1 file changed, 33 insertions(+), 11 deletions(-)
> > 
> > diff --git a/src/min_dio_alignment.c b/src/min_dio_alignment.c
> > index 866fba1546c4..143cee684ab4 100644
> > --- a/src/min_dio_alignment.c
> > +++ b/src/min_dio_alignment.c
> > @@ -1,17 +1,19 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  /*
> > - * Copyright (c) 2024 Christoph Hellwig
> > + * Copyright (c) 2024,2026 Christoph Hellwig
> >   */
> >  #include <fcntl.h>
> > +#include <stdbool.h>
> >  #include <stdio.h>
> >  #include <stdlib.h>
> >  #include <unistd.h>
> > +#include <getopt.h>
> >  #include <sys/mount.h>
> >  #include <sys/ioctl.h>
> >  #include <sys/stat.h>
> >  #include "statx.h"
> >  
> > -static int min_dio_alignment(const char *mntpnt, const char *devname)
> > +static int min_dio_alignment(const char *mntpnt, const char *devname, bool read)
> >  {
> >  	struct statx stx = { };
> >  	struct stat st;
> > @@ -27,9 +29,16 @@ static int min_dio_alignment(const char *mntpnt, const char *devname)
> >  	 */
> >  	fd = open(mntpnt, O_TMPFILE | O_RDWR | O_EXCL, 0600);
> >  	if (fd >= 0 &&
> > -	    xfstests_statx(fd, "", AT_EMPTY_PATH, STATX_DIOALIGN, &stx) == 0 &&
> > -	    (stx.stx_mask & STATX_DIOALIGN) && stx.stx_dio_offset_align != 0)
> > -		return stx.stx_dio_offset_align;
> > +	    xfstests_statx(fd, "", AT_EMPTY_PATH, STATX_DIOALIGN, &stx) == 0) {
> 
> 
> Hmm... shouldn't STATX_DIO_READ_ALIGN be passed in the request mask as well?
> 
>   xfstests_statx(fd, "", AT_EMPTY_PATH,
>                  STATX_DIOALIGN|STATX_DIO_READ_ALIGN, &stx)

Yeah, strictly speaking we should.  Currently this is only supported
for XFS, and XFS automatically adds STATX_DIO_READ_ALIGN when
STATX_DIOALIGN is requested, so it works.  But more by chance than
design.