xfs: disable the agi rotor for metadata inodes

Ideally, we'd put all the metadata inodes in one place if we could, so
that the metadata all stay reasonably close together instead of
spreading out over the disk.  Furthermore, if the log is internal we'd
probably prefer to keep the metadata near the log.  Therefore, disable
AGI rotoring for metadata inode allocations.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 40 insertions, 18 deletions

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index f0261c4d9106..8b84e2cf711b 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -1842,6 +1842,40 @@ out_release:
 }
 
 /*
+ * Pick an AG for the new inode.
+ *
+ * Directories, symlinks, and regular files frequently allocate at least one
+ * block, so factor that potential expansion when we examine whether an AG has
+ * enough space for file creation.  Try to keep metadata files all in the same
+ * AG.
+ */
+static inline xfs_agnumber_t
+xfs_dialloc_pick_ag(
+	struct xfs_mount	*mp,
+	struct xfs_inode	*dp,
+	umode_t			mode)
+{
+	xfs_agnumber_t		start_agno;
+
+	if (!dp)
+		return 0;
+	if (xfs_is_metadir_inode(dp)) {
+		if (mp->m_sb.sb_logstart)
+			return XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart);
+		return 0;
+	}
+
+	if (S_ISDIR(mode))
+		return (atomic_inc_return(&mp->m_agirotor) - 1) % mp->m_maxagi;
+
+	start_agno = XFS_INO_TO_AGNO(mp, dp->i_ino);
+	if (start_agno >= mp->m_maxagi)
+		start_agno = 0;
+
+	return start_agno;
+}
+
+/*
  * Allocate an on-disk inode.
  *
  * Mode is used to tell whether the new inode is a directory and hence where to
@@ -1856,31 +1890,19 @@ xfs_dialloc(
 	xfs_ino_t		*new_ino)
 {
 	struct xfs_mount	*mp = (*tpp)->t_mountp;
+	struct xfs_perag	*pag;
+	struct xfs_ino_geometry	*igeo = M_IGEO(mp);
+	xfs_ino_t		ino = NULLFSINO;
 	xfs_ino_t		parent = args->pip ? args->pip->i_ino : 0;
-	umode_t			mode = args->mode & S_IFMT;
 	xfs_agnumber_t		agno;
-	int			error = 0;
 	xfs_agnumber_t		start_agno;
-	struct xfs_perag	*pag;
-	struct xfs_ino_geometry	*igeo = M_IGEO(mp);
+	umode_t			mode = args->mode & S_IFMT;
 	bool			ok_alloc = true;
 	bool			low_space = false;
 	int			flags;
-	xfs_ino_t		ino = NULLFSINO;
+	int			error = 0;
 
-	/*
-	 * Directories, symlinks, and regular files frequently allocate at least
-	 * one block, so factor that potential expansion when we examine whether
-	 * an AG has enough space for file creation.
-	 */
-	if (S_ISDIR(mode))
-		start_agno = (atomic_inc_return(&mp->m_agirotor) - 1) %
-				mp->m_maxagi;
-	else {
-		start_agno = XFS_INO_TO_AGNO(mp, parent);
-		if (start_agno >= mp->m_maxagi)
-			start_agno = 0;
-	}
+	start_agno = xfs_dialloc_pick_ag(mp, args->pip, mode);
 
 	/*
 	 * If we have already hit the ceiling of inode blocks then clear