diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index b599e6b..25e5eae 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -140,6 +140,8 @@
 	pct = in->imaxpct;
 	if (nb < mp->m_sb.sb_dblocks || pct < 0 || pct > 100)
 		return XFS_ERROR(EINVAL);
+	if ((error = xfs_sb_validate_fsb_count(&mp->m_sb, nb)))
+		return error;
 	dpct = pct - mp->m_sb.sb_imax_pct;
 	error = xfs_read_buf(mp, mp->m_ddev_targp,
 			XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1),
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index a96bde6..5de1f39 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -202,6 +202,27 @@
 	kmem_free(mp, sizeof(xfs_mount_t));
 }
 
+/*
+ * Check size of device based on the (data/realtime) block count.
+ * Note: this check is used by the growfs code as well as mount.
+ */
+int
+xfs_sb_validate_fsb_count(
+	xfs_sb_t	*sbp,
+	__uint64_t	nblocks)
+{
+	ASSERT(PAGE_SHIFT >= sbp->sb_blocklog);
+	ASSERT(sbp->sb_blocklog >= BBSHIFT);
+
+#if XFS_BIG_BLKNOS     /* Limited by ULONG_MAX of page cache index */
+	if (nblocks >> (PAGE_CACHE_SHIFT - sbp->sb_blocklog) > ULONG_MAX)
+		return E2BIG;
+#else                  /* Limited by UINT_MAX of sectors */
+	if (nblocks << (sbp->sb_blocklog - BBSHIFT) > UINT_MAX)
+		return E2BIG;
+#endif
+	return 0;
+}
 
 /*
  * Check the validity of the SB found.
@@ -284,18 +305,8 @@
 		return XFS_ERROR(EFSCORRUPTED);
 	}
 
-	ASSERT(PAGE_SHIFT >= sbp->sb_blocklog);
-	ASSERT(sbp->sb_blocklog >= BBSHIFT);
-
-#if XFS_BIG_BLKNOS     /* Limited by ULONG_MAX of page cache index */
-	if (unlikely(
-	    (sbp->sb_dblocks >> (PAGE_SHIFT - sbp->sb_blocklog)) > ULONG_MAX ||
-	    (sbp->sb_rblocks >> (PAGE_SHIFT - sbp->sb_blocklog)) > ULONG_MAX)) {
-#else                  /* Limited by UINT_MAX of sectors */
-	if (unlikely(
-	    (sbp->sb_dblocks << (sbp->sb_blocklog - BBSHIFT)) > UINT_MAX ||
-	    (sbp->sb_rblocks << (sbp->sb_blocklog - BBSHIFT)) > UINT_MAX)) {
-#endif
+	if (xfs_sb_validate_fsb_count(sbp, sbp->sb_dblocks) ||
+	    xfs_sb_validate_fsb_count(sbp, sbp->sb_rblocks)) {
 		xfs_fs_mount_cmn_err(flags,
 			"file system too large to be mounted on this system.");
 		return XFS_ERROR(E2BIG);
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 82304b9..871a5bf 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -624,6 +624,7 @@
 extern xfs_agnumber_t	xfs_initialize_perag(struct bhv_vfs *, xfs_mount_t *,
 						xfs_agnumber_t);
 extern void	xfs_xlatesb(void *, struct xfs_sb *, int, __int64_t);
+extern int	xfs_sb_validate_fsb_count(struct xfs_sb *, __uint64_t);
 
 extern struct xfs_dmops xfs_dmcore_stub;
 extern struct xfs_qmops xfs_qmcore_stub;
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index b3a5f07..47082c0 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -1882,11 +1882,13 @@
 	    (nrblocks = in->newblocks) <= sbp->sb_rblocks ||
 	    (sbp->sb_rblocks && (in->extsize != sbp->sb_rextsize)))
 		return XFS_ERROR(EINVAL);
+	if ((error = xfs_sb_validate_fsb_count(sbp, nrblocks)))
+		return error;
 	/*
 	 * Read in the last block of the device, make sure it exists.
 	 */
 	error = xfs_read_buf(mp, mp->m_rtdev_targp,
-			XFS_FSB_TO_BB(mp, in->newblocks - 1),
+			XFS_FSB_TO_BB(mp, nrblocks - 1),
 			XFS_FSB_TO_BB(mp, 1), 0, &bp);
 	if (error)
 		return error;