Re: [PATCH 1/9] seek_sanity_test: fix allocation unit detection on XFS realtime

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Jul 28, 2022 at 03:38:38AM +0000, liuyd.fnst@fujitsu.com wrote:
> Hi, Darrick.
> 
> 
> On 7/28/22 10:37, Darrick J. Wong wrote:
> > Does this patch fix NFS for you?
> 
> It works for me. Thanks.
> BTW. It has conflict during "git am". Looks like your branch are ahead 
> of master.

Yes, I base my development branch off of for-next nowadays.  Thanks for
the report, I'll add a tested-by if that's ok and send it out as a bug
fix.

--D

> > 
> > --D
> > ---
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > seek_sanity_test: use XFS ioctls to determine file allocation unit size
> > 
> > liuyd.fnst@fujitsu.com reported that my recent change to the seek sanity
> > test broke NFS.  I foolishly thought that st_blksize was sufficient to
> > find the file allocation unit size so that applications could figure out
> > the SEEK_HOLE granularity.  Replace that with an explicit callout to XFS
> > ioctls so that xfs realtime will work again.
> > 
> > Fixes: e861a302 ("seek_sanity_test: fix allocation unit detection on XFS realtime")
> > Reported-by: liuyd.fnst@fujitsu.com
> > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > ---
> >   src/Makefile           |    4 ++++
> >   src/seek_sanity_test.c |   40 +++++++++++++++++++++++++++++++---------
> >   2 files changed, 35 insertions(+), 9 deletions(-)
> > 
> > diff --git a/src/Makefile b/src/Makefile
> > index 38628a22..b89a7a5e 100644
> > --- a/src/Makefile
> > +++ b/src/Makefile
> > @@ -82,6 +82,10 @@ ifeq ($(HAVE_LIBCAP), true)
> >   LLDLIBS += -lcap
> >   endif
> >   
> > +ifeq ($(HAVE_FSXATTR_XFLAG_HASATTR), yes)
> > +LCFLAGS += -DHAVE_FSXATTR_XFLAG_HASATTR
> > +endif
> > +
> >   ifeq ($(HAVE_SEEK_DATA), yes)
> >    ifeq ($(HAVE_FSXATTR_XFLAG_HASATTR), yes)
> >     ifeq ($(HAVE_NFTW), yes)
> > diff --git a/src/seek_sanity_test.c b/src/seek_sanity_test.c
> > index 1030d0c5..b53f4862 100644
> > --- a/src/seek_sanity_test.c
> > +++ b/src/seek_sanity_test.c
> > @@ -40,6 +40,32 @@ static void get_file_system(int fd)
> >   	}
> >   }
> >   
> > +#ifdef HAVE_FSXATTR_XFLAG_HASATTR
> > +/* Compute the file allocation unit size for an XFS file. */
> > +static int detect_xfs_alloc_unit(int fd)
> > +{
> > +	struct fsxattr fsx;
> > +	struct xfs_fsop_geom fsgeom;
> > +	int ret;
> > +
> > +	ret = ioctl(fd, XFS_IOC_FSGEOMETRY, &fsgeom);
> > +	if (ret)
> > +		return -1;
> > +
> > +	ret = ioctl(fd, FS_IOC_FSGETXATTR, &fsx);
> > +	if (ret)
> > +		return -1;
> > +
> > +	alloc_size = fsgeom.blocksize;
> > +	if (fsx.fsx_xflags & FS_XFLAG_REALTIME)
> > +		alloc_size *= fsgeom.rtextsize;
> > +
> > +	return 0;
> > +}
> > +#else
> > +# define detect_xfs_alloc_unit(fd) (-1)
> > +#endif
> > +
> >   static int get_io_sizes(int fd)
> >   {
> >   	off_t pos = 0, offset = 1;
> > @@ -47,6 +73,10 @@ static int get_io_sizes(int fd)
> >   	int shift, ret;
> >   	int pagesz = sysconf(_SC_PAGE_SIZE);
> >   
> > +	ret = detect_xfs_alloc_unit(fd);
> > +	if (!ret)
> > +		goto done;
> > +
> >   	ret = fstat(fd, &buf);
> >   	if (ret) {
> >   		fprintf(stderr, "  ERROR %d: Failed to find io blocksize\n",
> > @@ -54,16 +84,8 @@ static int get_io_sizes(int fd)
> >   		return ret;
> >   	}
> >   
> > -	/*
> > -	 * st_blksize is typically also the allocation size.  However, XFS
> > -	 * rounds this up to the page size, so if the stat blocksize is exactly
> > -	 * one page, use this iterative algorithm to see if SEEK_DATA will hint
> > -	 * at a more precise answer based on the filesystem's (pre)allocation
> > -	 * decisions.
> > -	 */
> > +	/* st_blksize is typically also the allocation size */
> >   	alloc_size = buf.st_blksize;
> > -	if (alloc_size != pagesz)
> > -		goto done;
> >   
> >   	/* try to discover the actual alloc size */
> >   	while (pos == 0 && offset < alloc_size) {