diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index c6a617dada27..098b46f3f3e3 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3221,68 +3221,6 @@ xfs_bmap_btalloc_select_lengths(
 	return 0;
 }
 
-static int
-xfs_bmap_btalloc_filestreams_select_lengths(
-	struct xfs_bmalloca	*ap,
-	struct xfs_alloc_arg	*args,
-	xfs_extlen_t		*blen)
-{
-	struct xfs_mount	*mp = ap->ip->i_mount;
-	struct xfs_perag	*pag;
-	xfs_agnumber_t		start_agno;
-	int			error;
-
-	args->total = ap->total;
-
-	start_agno = XFS_FSB_TO_AGNO(mp, ap->blkno);
-	if (start_agno == NULLAGNUMBER)
-		start_agno = 0;
-
-	pag = xfs_perag_grab(mp, start_agno);
-	if (pag) {
-		error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
-		xfs_perag_rele(pag);
-		if (error) {
-			if (error != -EAGAIN)
-				return error;
-			*blen = 0;
-		}
-	}
-
-	if (*blen < args->maxlen) {
-		xfs_agnumber_t	agno = start_agno;
-
-		error = xfs_filestream_new_ag(ap, &agno);
-		if (error)
-			return error;
-		if (agno == NULLAGNUMBER)
-			goto out_select;
-
-		pag = xfs_perag_grab(mp, agno);
-		if (!pag)
-			goto out_select;
-
-		error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
-		xfs_perag_rele(pag);
-		if (error) {
-			if (error != -EAGAIN)
-				return error;
-			*blen = 0;
-		}
-		start_agno = agno;
-	}
-
-out_select:
-	args->minlen = xfs_bmap_select_minlen(ap, args, *blen);
-
-	/*
-	 * Set the failure fallback case to look in the selected AG as stream
-	 * may have moved.
-	 */
-	ap->blkno = args->fsbno = XFS_AGB_TO_FSB(mp, start_agno, 0);
-	return 0;
-}
-
 /* Update all inode and quota accounting for the allocation we just did. */
 static void
 xfs_bmap_btalloc_accounting(
@@ -3576,7 +3514,7 @@ xfs_bmap_btalloc_at_eof(
  * transaction that we are critically low on space so they don't waste time on
  * allocation modes that are unlikely to succeed.
  */
-static int
+int
 xfs_bmap_btalloc_low_space(
 	struct xfs_bmalloca	*ap,
 	struct xfs_alloc_arg	*args)
@@ -3605,36 +3543,25 @@ xfs_bmap_btalloc_filestreams(
 	struct xfs_alloc_arg	*args,
 	int			stripe_align)
 {
-	xfs_agnumber_t		agno = xfs_filestream_lookup_ag(ap->ip);
 	xfs_extlen_t		blen = 0;
 	int			error;
 
-	/* Determine the initial block number we will target for allocation. */
-	if (agno == NULLAGNUMBER)
-		agno = 0;
-	ap->blkno = XFS_AGB_TO_FSB(args->mp, agno, 0);
-	xfs_bmap_adjacent(ap);
+
+	error = xfs_filestream_select_ag(ap, args, &blen);
+	if (error)
+		return error;
 
 	/*
-	 * If there is very little free space before we start a
-	 * filestreams allocation, we're almost guaranteed to fail to
-	 * find an AG with enough contiguous free space to succeed, so
-	 * just go straight to the low space algorithm.
+	 * If we are in low space mode, then optimal allocation will fail so
+	 * prepare for minimal allocation and jump to the low space algorithm
+	 * immediately.
 	 */
 	if (ap->tp->t_flags & XFS_TRANS_LOWMODE) {
 		args->minlen = ap->minlen;
-		return xfs_bmap_btalloc_low_space(ap, args);
+		goto out_low_space;
 	}
 
-	/*
-	 * Search for an allocation group with a single extent large enough for
-	 * the request.  If one isn't found, then adjust the minimum allocation
-	 * size to the largest space found.
-	 */
-	error = xfs_bmap_btalloc_filestreams_select_lengths(ap, args, &blen);
-	if (error)
-		return error;
-
+	args->minlen = xfs_bmap_select_minlen(ap, args, blen);
 	if (ap->aeof) {
 		error = xfs_bmap_btalloc_at_eof(ap, args, blen, stripe_align,
 				true);
@@ -3646,6 +3573,7 @@ xfs_bmap_btalloc_filestreams(
 	if (error || args->fsbno != NULLFSBLOCK)
 		return error;
 
+out_low_space:
 	return xfs_bmap_btalloc_low_space(ap, args);
 }
 
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index 7bd619eb2f7d..94d9285eeba1 100644
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -12,6 +12,7 @@ struct xfs_ifork;
 struct xfs_inode;
 struct xfs_mount;
 struct xfs_trans;
+struct xfs_alloc_arg;
 
 /*
  * Argument structure for xfs_bmap_alloc.
@@ -224,6 +225,8 @@ int	xfs_bmap_add_extent_unwritten_real(struct xfs_trans *tp,
 		struct xfs_bmbt_irec *new, int *logflagsp);
 xfs_extlen_t xfs_bmapi_minleft(struct xfs_trans *tp, struct xfs_inode *ip,
 		int fork);
+int	xfs_bmap_btalloc_low_space(struct xfs_bmalloca *ap,
+		struct xfs_alloc_arg *args);
 
 enum xfs_bmap_intent_type {
 	XFS_BMAP_MAP = 1,
diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
index 2eb702034d05..a641404aa9a6 100644
--- a/fs/xfs/xfs_filestream.c
+++ b/fs/xfs/xfs_filestream.c
@@ -12,6 +12,7 @@
 #include "xfs_mount.h"
 #include "xfs_inode.h"
 #include "xfs_bmap.h"
+#include "xfs_bmap_util.h"
 #include "xfs_alloc.h"
 #include "xfs_mru_cache.h"
 #include "xfs_trace.h"
@@ -263,7 +264,7 @@ xfs_filestream_get_parent(
  *
  * Returns NULLAGNUMBER in case of an error.
  */
-xfs_agnumber_t
+static xfs_agnumber_t
 xfs_filestream_lookup_ag(
 	struct xfs_inode	*ip)
 {
@@ -312,7 +313,7 @@ xfs_filestream_lookup_ag(
  * This is called when the allocator can't find a suitable extent in the
  * current AG, and we have to move the stream into a new AG with more space.
  */
-int
+static int
 xfs_filestream_new_ag(
 	struct xfs_bmalloca	*ap,
 	xfs_agnumber_t		*agp)
@@ -358,6 +359,101 @@ xfs_filestream_new_ag(
 	return err;
 }
 
+static int
+xfs_filestreams_select_lengths(
+	struct xfs_bmalloca	*ap,
+	struct xfs_alloc_arg	*args,
+	xfs_extlen_t		*blen)
+{
+	struct xfs_mount	*mp = ap->ip->i_mount;
+	struct xfs_perag	*pag;
+	xfs_agnumber_t		start_agno;
+	int			error;
+
+	args->total = ap->total;
+
+	start_agno = XFS_FSB_TO_AGNO(mp, ap->blkno);
+	if (start_agno == NULLAGNUMBER)
+		start_agno = 0;
+
+	pag = xfs_perag_grab(mp, start_agno);
+	if (pag) {
+		error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
+		xfs_perag_rele(pag);
+		if (error) {
+			if (error != -EAGAIN)
+				return error;
+			*blen = 0;
+		}
+	}
+
+	if (*blen < args->maxlen) {
+		xfs_agnumber_t	agno = start_agno;
+
+		error = xfs_filestream_new_ag(ap, &agno);
+		if (error)
+			return error;
+		if (agno == NULLAGNUMBER)
+			goto out_select;
+
+		pag = xfs_perag_grab(mp, agno);
+		if (!pag)
+			goto out_select;
+
+		error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
+		xfs_perag_rele(pag);
+		if (error) {
+			if (error != -EAGAIN)
+				return error;
+			*blen = 0;
+		}
+		start_agno = agno;
+	}
+
+out_select:
+	/*
+	 * Set the failure fallback case to look in the selected AG as stream
+	 * may have moved.
+	 */
+	ap->blkno = args->fsbno = XFS_AGB_TO_FSB(mp, start_agno, 0);
+	return 0;
+}
+
+/*
+ * Search for an allocation group with a single extent large enough for
+ * the request.  If one isn't found, then the largest available free extent is
+ * returned as the best length possible.
+ */
+int
+xfs_filestream_select_ag(
+	struct xfs_bmalloca	*ap,
+	struct xfs_alloc_arg	*args,
+	xfs_extlen_t		*blen)
+{
+	xfs_agnumber_t		start_agno = xfs_filestream_lookup_ag(ap->ip);
+
+	/* Determine the initial block number we will target for allocation. */
+	if (start_agno == NULLAGNUMBER)
+		start_agno = 0;
+	ap->blkno = XFS_AGB_TO_FSB(args->mp, start_agno, 0);
+	xfs_bmap_adjacent(ap);
+
+	/*
+	 * If there is very little free space before we start a filestreams
+	 * allocation, we're almost guaranteed to fail to find a better AG with
+	 * larger free space available so we don't even try.
+	 */
+	if (ap->tp->t_flags & XFS_TRANS_LOWMODE)
+		return 0;
+
+	/*
+	 * Search for an allocation group with a single extent large enough for
+	 * the request.  If one isn't found, then adjust the minimum allocation
+	 * size to the largest space found.
+	 */
+	return xfs_filestreams_select_lengths(ap, args, blen);
+}
+
 void
 xfs_filestream_deassociate(
 	struct xfs_inode	*ip)
diff --git a/fs/xfs/xfs_filestream.h b/fs/xfs/xfs_filestream.h
index 403226ebb80b..df9f7553e106 100644
--- a/fs/xfs/xfs_filestream.h
+++ b/fs/xfs/xfs_filestream.h
@@ -9,13 +9,14 @@
 struct xfs_mount;
 struct xfs_inode;
 struct xfs_bmalloca;
+struct xfs_alloc_arg;
 
 int xfs_filestream_mount(struct xfs_mount *mp);
 void xfs_filestream_unmount(struct xfs_mount *mp);
 void xfs_filestream_deassociate(struct xfs_inode *ip);
-xfs_agnumber_t xfs_filestream_lookup_ag(struct xfs_inode *ip);
-int xfs_filestream_new_ag(struct xfs_bmalloca *ap, xfs_agnumber_t *agp);
 int xfs_filestream_peek_ag(struct xfs_mount *mp, xfs_agnumber_t agno);
+int xfs_filestream_select_ag(struct xfs_bmalloca *ap,
+		struct xfs_alloc_arg *args, xfs_extlen_t *blen);
 
 static inline int
 xfs_inode_is_filestream(
