diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 31fd65b3aaa9..0e4e2df08aed 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -211,6 +211,23 @@ xfs_rtallocate_range(
 	return error;
 }
 
+/*
+ * Make sure we don't run off the end of the rt volume.  Be careful that
+ * adjusting maxlen downwards doesn't cause us to fail the alignment checks.
+ */
+static inline xfs_extlen_t
+xfs_rtallocate_clamp_len(
+	struct xfs_mount	*mp,
+	xfs_rtblock_t		startrtx,
+	xfs_extlen_t		rtxlen,
+	xfs_extlen_t		prod)
+{
+	xfs_extlen_t		ret;
+
+	ret = min(mp->m_sb.sb_rextents, startrtx + rtxlen) - startrtx;
+	return rounddown(ret, prod);
+}
+
 /*
  * Attempt to allocate an extent minlen<=len<=maxlen starting from
  * bitmap block bbno.  If we don't get maxlen then use prod to trim
@@ -248,7 +265,7 @@ xfs_rtallocate_extent_block(
 	     i <= end;
 	     i++) {
 		/* Make sure we don't scan off the end of the rt volume. */
-		maxlen = min(mp->m_sb.sb_rextents, i + maxlen) - i;
+		maxlen = xfs_rtallocate_clamp_len(mp, i, maxlen, prod);
 
 		/*
 		 * See if there's a free extent of maxlen starting at i.
@@ -355,7 +372,8 @@ xfs_rtallocate_extent_exact(
 	int		isfree;		/* extent is free */
 	xfs_rtblock_t	next;		/* next block to try (dummy) */
 
-	ASSERT(minlen % prod == 0 && maxlen % prod == 0);
+	ASSERT(minlen % prod == 0);
+	ASSERT(maxlen % prod == 0);
 	/*
 	 * Check if the range in question (for maxlen) is free.
 	 */
@@ -438,7 +456,9 @@ xfs_rtallocate_extent_near(
 	xfs_rtblock_t	n;		/* next block to try */
 	xfs_rtblock_t	r;		/* result block */
 
-	ASSERT(minlen % prod == 0 && maxlen % prod == 0);
+	ASSERT(minlen % prod == 0);
+	ASSERT(maxlen % prod == 0);
+
 	/*
 	 * If the block number given is off the end, silently set it to
 	 * the last block.
@@ -447,7 +467,7 @@ xfs_rtallocate_extent_near(
 		bno = mp->m_sb.sb_rextents - 1;
 
 	/* Make sure we don't run off the end of the rt volume. */
-	maxlen = min(mp->m_sb.sb_rextents, bno + maxlen) - bno;
+	maxlen = xfs_rtallocate_clamp_len(mp, bno, maxlen, prod);
 	if (maxlen < minlen) {
 		*rtblock = NULLRTBLOCK;
 		return 0;
@@ -638,7 +658,8 @@ xfs_rtallocate_extent_size(
 	xfs_rtblock_t	r;		/* result block number */
 	xfs_suminfo_t	sum;		/* summary information for extents */
 
-	ASSERT(minlen % prod == 0 && maxlen % prod == 0);
+	ASSERT(minlen % prod == 0);
+	ASSERT(maxlen % prod == 0);
 	ASSERT(maxlen != 0);
 
 	/*