xfs: move xfs_bmap_btalloc_filestreams() to xfs_filestreams.c

xfs_bmap_btalloc_filestreams() calls two filestreams functions to
select the AG to allocate from. Both those functions end up in
the same selection function that iterates all AGs multiple times.
Worst case, xfs_bmap_btalloc_filestreams() can iterate all AGs 4
times just to select the initial AG to allocate in.

Move the AG selection to fs/xfs/xfs_filestreams.c as a single
interface so that the inefficient AG interation is contained
entirely within the filestreams code. This will allow the
implementation to be simplified and made more efficient in future
patches.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 98 insertions, 2 deletions

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 @@ out:
  *
  * 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 @@ out:
  * 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 @@ exit:
 	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)