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
Tested-by: liuyd.fnst@fujitsu.com
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>

diff --git a/src/seek_sanity_test.c b/src/seek_sanity_test.c
index 1030d0c564bee26c7d5ad636ef7e3305c1b16d5c..78f835e8837b96d663399d3d9bddaec170fb7ff2 100644 (file)
--- a/src/seek_sanity_test.c
+++ b/src/seek_sanity_test.c
@@ -40,6 +40,28 @@ static void get_file_system(int fd)
        }
 }
 
        }
 }
 

+/* 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, XFS_IOC_FSGETXATTR, &fsx);
+       if (ret)
+               return -1;
+
+       alloc_size = fsgeom.blocksize;
+       if (fsx.fsx_xflags & XFS_XFLAG_REALTIME)
+               alloc_size *= fsgeom.rtextsize;
+
+       return 0;
+}
+

 static int get_io_sizes(int fd)
 {
        off_t pos = 0, offset = 1;
 static int get_io_sizes(int fd)
 {
        off_t pos = 0, offset = 1;


@@ -47,6 +69,10 @@ static int get_io_sizes(int fd)
        int shift, ret;
        int pagesz = sysconf(_SC_PAGE_SIZE);
 
        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",
        ret = fstat(fd, &buf);
        if (ret) {
                fprintf(stderr, "  ERROR %d: Failed to find io blocksize\n",


@@ -54,16 +80,8 @@ static int get_io_sizes(int fd)
                return ret;
        }
 
                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;
        alloc_size = buf.st_blksize;

-       if (alloc_size != pagesz)
-               goto done;

 
        /* try to discover the actual alloc size */
        while (pos == 0 && offset < alloc_size) {
 
        /* try to discover the actual alloc size */
        while (pos == 0 && offset < alloc_size) {