xfs: factor out MRU hit case in xfs_filestream_select_ag

Because it now stands out like a sore thumb. Factoring out this case
starts the process of simplifying xfs_filestream_select_ag() again.

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

fs/xfs/xfs_filestream.c

@@ -259,10 +259,85 @@ xfs_filestream_get_parent(
 	return dir ? XFS_I(dir) : NULL;
 }
 
+/*
+ * Lookup the mru cache for an existing association. If one exists and we can
+ * use it, return with the agno and blen indicating that the allocation will
+ * proceed with that association.
+ *
+ * If we have no association, or we cannot use the current one and have to
+ * destroy it, return with blen = 0 and agno pointing at the next agno to try.
+ */
+int
+xfs_filestream_select_ag_mru(
+	struct xfs_bmalloca	*ap,
+	struct xfs_alloc_arg	*args,
+	struct xfs_inode	*pip,
+	xfs_agnumber_t		*agno,
+	xfs_extlen_t		*blen)
+{
+	struct xfs_mount	*mp = ap->ip->i_mount;
+	struct xfs_perag	*pag;
+	struct xfs_mru_cache_elem *mru;
+	int			error;
+
+	mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
+	if (!mru)
+		goto out_default_agno;
+
+	*agno = container_of(mru, struct xfs_fstrm_item, mru)->ag;
+	xfs_mru_cache_done(mp->m_filestream);
+
+	trace_xfs_filestream_lookup(mp, ap->ip->i_ino, *agno);
+
+	ap->blkno = XFS_AGB_TO_FSB(args->mp, *agno, 0);
+	xfs_bmap_adjacent(ap);
+
+	pag = xfs_perag_grab(mp, *agno);
+	if (!pag)
+		goto out_default_agno;
+
+	error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
+	xfs_perag_rele(pag);
+	if (error) {
+		if (error != -EAGAIN)
+			return error;
+		*blen = 0;
+	}
+
+	/*
+	 * We are done if there's still enough contiguous free space to succeed.
+	 */
+	if (*blen >= args->maxlen)
+		return 0;
+
+	/* Changing parent AG association now, so remove the existing one. */
+	mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
+	if (mru) {
+		struct xfs_fstrm_item *item =
+			container_of(mru, struct xfs_fstrm_item, mru);
+		*agno = (item->ag + 1) % mp->m_sb.sb_agcount;
+		xfs_fstrm_free_func(mp, mru);
+		return 0;
+	}
+
+out_default_agno:
+	if (xfs_is_inode32(mp)) {
+		xfs_agnumber_t	 rotorstep = xfs_rotorstep;
+		*agno = (mp->m_agfrotor / rotorstep) %
+				mp->m_sb.sb_agcount;
+		mp->m_agfrotor = (mp->m_agfrotor + 1) %
+				 (mp->m_sb.sb_agcount * rotorstep);
+		return 0;
+	}
+	*agno = XFS_INO_TO_AGNO(mp, pip->i_ino);
+	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.
+ * the request.  If one isn't found, then adjust the minimum allocation
+ * size to the largest space found.
  */
 int
 xfs_filestream_select_ag(
@@ -271,12 +346,10 @@ xfs_filestream_select_ag(
 	xfs_extlen_t		*blen)
 {
 	struct xfs_mount	*mp = ap->ip->i_mount;
-	struct xfs_perag	*pag;
 	struct xfs_inode	*pip = NULL;
-	xfs_agnumber_t		agno = NULLAGNUMBER;
-	struct xfs_mru_cache_elem *mru;
+	xfs_agnumber_t		agno;
 	int			flags = 0;
-	int			error = 0;
+	int			error;
 
 	args->total = ap->total;
 	*blen = 0;
@@ -287,48 +360,10 @@ xfs_filestream_select_ag(
 		goto out_select;
 	}
 
-	mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
-	if (mru) {
-		agno = container_of(mru, struct xfs_fstrm_item, mru)->ag;
-		xfs_mru_cache_done(mp->m_filestream);
-		mru = NULL;
-
-		trace_xfs_filestream_lookup(mp, ap->ip->i_ino, agno);
-		xfs_irele(pip);
-
-		ap->blkno = XFS_AGB_TO_FSB(args->mp, agno, 0);
-		xfs_bmap_adjacent(ap);
-
-		pag = xfs_perag_grab(mp, agno);
-		if (pag) {
-			error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
-			xfs_perag_rele(pag);
-			if (error) {
-				if (error != -EAGAIN)
-					goto out_error;
-				*blen = 0;
-			}
-		}
-		if (*blen >= args->maxlen)
-			goto out_select;
-	} else if (xfs_is_inode32(mp)) {
-		xfs_agnumber_t	 rotorstep = xfs_rotorstep;
-		agno = (mp->m_agfrotor / rotorstep) %
-				mp->m_sb.sb_agcount;
-		mp->m_agfrotor = (mp->m_agfrotor + 1) %
-				 (mp->m_sb.sb_agcount * rotorstep);
-	} else {
-		agno = XFS_INO_TO_AGNO(mp, pip->i_ino);
-	}
+	error = xfs_filestream_select_ag_mru(ap, args, pip, &agno, blen);
+	if (error || *blen >= args->maxlen)
+		goto out_rele;
 
-	/* Changing parent AG association now, so remove the existing one. */
-	mru = xfs_mru_cache_remove(mp->m_filestream, pip->i_ino);
-	if (mru) {
-		struct xfs_fstrm_item *item =
-			container_of(mru, struct xfs_fstrm_item, mru);
-		agno = (item->ag + 1) % mp->m_sb.sb_agcount;
-		xfs_fstrm_free_func(mp, mru);
-	}
 	ap->blkno = XFS_AGB_TO_FSB(args->mp, agno, 0);
 	xfs_bmap_adjacent(ap);
 
@@ -347,16 +382,14 @@ xfs_filestream_select_ag(
 
 	*blen = ap->length;
 	error = xfs_filestream_pick_ag(pip, &agno, flags, blen);
-	if (error)
-		goto out_error;
 	if (agno == NULLAGNUMBER) {
 		agno = 0;
 		*blen = 0;
 	}
 
 out_select:
 	ap->blkno = XFS_AGB_TO_FSB(mp, agno, 0);
-out_error:
+out_rele:
 	xfs_irele(pip);
 	return error;