mkfs: get sector size from host fs dev when mkfs'ing file

Now that we allow logical-sector-sized DIOs even if our xfs filesystem is set to physical-sector-sized "sectors," we can allow the creation of filesystem images with block and sector sizes down to the host device's logical sector size, rather than the filesystem's sector size.

So in platform_findsizes(), change our query of the filesystem to a query of the device, and use that for sector size in the S_IFREG case.

This allows the creation of i.e. a 2k block sized image on an xfs filesystem w/ 4k sector size created on a 4k/512 block device, which would otherwise fail today.

Signed-off-by Eric Sandeen <[email protected]>

---

This feels like about my 5th stab at this; it seems like the correct thing to do but by now my brain is full. Seem sane?

Still needs a run through xfstests but wanted to see if this was obviously bonkers or not...?

(I don't know why copy/Makefile needs a $(LIBBLKID), either...)

index 885016a..3a8dc12 100644

libxfs/linux.c +11 -9

@@ -24,6 +24,7 @@
 #include <sys/mount.h>
 #include <sys/ioctl.h>
 #include <sys/sysinfo.h>
+#include <blkid/blkid.h>
 
 #include "libxfs_priv.h"
 #include "xfs_fs.h"

@@ -142,18 +143,29 @@ platform_findsizes(char *path, int fd, long long *sz, int *bsz)
 			progname, path, strerror(errno));
 		exit(1);
 	}
+
 	if ((st.st_mode & S_IFMT) == S_IFREG) {
-		struct xfs_fsop_geom_v1 geom = { 0 };
+		int	fd;
+		char	*hostfs_dev_path;	/* path to host fs device */
 
 		*sz = (long long)(st.st_size >> 9);
-		if (ioctl(fd, XFS_IOC_FSGEOMETRY_V1, &geom) < 0) {
-			/*
-			 * fall back to BBSIZE; mkfs might fail if there's a
-			 * size mismatch between the image & the host fs...
-			 */
-			*bsz = BBSIZE;
-		} else
-			*bsz = geom.sectsize;
+
+		/*
+		 * Default to BBSIZE; mkfs might fail if there's a
+		 * size mismatch between the image & the host fs...
+		 */
+		*bsz = BBSIZE;
+

So the current behaviour is to use the underlying filesystem sector size, but we might have a 4k fs sector on a 512 physical sector device, and you want to detect this, right? The logical sector size is exposed by the filesystem in the XFS_IOC_DIOINFO information. i.e:

        case XFS_IOC_DIOINFO: {
                struct dioattr  da;
                xfs_buftarg_t   *target =
                        XFS_IS_REALTIME_INODE(ip) ?
                        mp->m_rtdev_targp : mp->m_ddev_targp;

                da.d_mem =  da.d_miniosz = target->bt_logical_sectorsize;
                da.d_maxiosz = INT_MAX & ~(da.d_miniosz - 1);

                if (copy_to_user(arg, &da, sizeof(da)))
                        return -EFAULT;
                return 0;
        }

Isn't this exactly what XFS_IOC_DIOINFO is for?