FreeBSD: Return 1 for _PC_MIN_HOLE_SIZE

The actual minimum hole size on ZFS is variable, but we always report
SPA_MINBLOCKSIZE, which is 512.  This may lead applications to believe
that they can reliably create holes at 512-byte boundaries and waste
resources trying to punch holes that ZFS ends up filling anyway.  It is
better to return 1 instead, as explained in pathconf(3):

  A special value of 1 is returned if the file system does not
  specify the minimum hole size but still reports holes.

Signed-off-by: Dag-Erling Smørgrav <[email protected]>

Author: dag-erling

module/os/freebsd/zfs/zfs_ctldir.c

@@ -760,7 +760,7 @@ zfsctl_common_pathconf(struct vop_pathconf_args *ap)
 		return (0);
 
 	case _PC_MIN_HOLE_SIZE:
-		*ap->a_retval = (int)SPA_MINBLOCKSIZE;
+		*ap->a_retval = 1;
 		return (0);
 
 	case _PC_ACL_EXTENDED:

module/os/freebsd/zfs/zfs_vnops_os.c

@@ -4122,7 +4122,7 @@ zfs_pathconf(vnode_t *vp, int cmd, ulong_t *valp, cred_t *cr,
 		*valp = 64;
 		return (0);
 	case _PC_MIN_HOLE_SIZE:
-		*valp = (int)SPA_MINBLOCKSIZE;
+		*valp = 1;
 		return (0);
 	case _PC_ACL_EXTENDED:
 #if 0		/* POSIX ACLs are not implemented for ZFS on FreeBSD yet. */