xfs: use xfs_alloc_vextent_first_ag() where appropriate

Change obvious callers of single AG allocation to use
xfs_alloc_vextent_first_ag(). This gets rid of
XFS_ALLOCTYPE_FIRST_AG as the type used within
xfs_alloc_vextent_first_ag() during iteration is _THIS_AG. Hence we
can remove the setting of args->type from all the callers of
_first_ag() and remove the alloctype.

While doing this, pass the allocation target fsb as a parameter
rather than encoding it in args->fsbno. This starts the process
of making args->fsbno an output only variable rather than
input/output.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/libxfs/xfs_alloc.c

@@ -3183,7 +3183,8 @@ xfs_alloc_read_agf(
  */
 static int
 xfs_alloc_vextent_check_args(
-	struct xfs_alloc_arg	*args)
+	struct xfs_alloc_arg	*args,
+	xfs_fsblock_t		target)
 {
 	struct xfs_mount	*mp = args->mp;
 	xfs_agblock_t		agsize;
@@ -3201,13 +3202,13 @@ xfs_alloc_vextent_check_args(
 		args->maxlen = agsize;
 	if (args->alignment == 0)
 		args->alignment = 1;
-	ASSERT(XFS_FSB_TO_AGNO(mp, args->fsbno) < mp->m_sb.sb_agcount);
-	ASSERT(XFS_FSB_TO_AGBNO(mp, args->fsbno) < agsize);
+	ASSERT(XFS_FSB_TO_AGNO(mp, target) < mp->m_sb.sb_agcount);
+	ASSERT(XFS_FSB_TO_AGBNO(mp, target) < agsize);
 	ASSERT(args->minlen <= args->maxlen);
 	ASSERT(args->minlen <= agsize);
 	ASSERT(args->mod < args->prod);
-	if (XFS_FSB_TO_AGNO(mp, args->fsbno) >= mp->m_sb.sb_agcount ||
-	    XFS_FSB_TO_AGBNO(mp, args->fsbno) >= agsize ||
+	if (XFS_FSB_TO_AGNO(mp, target) >= mp->m_sb.sb_agcount ||
+	    XFS_FSB_TO_AGBNO(mp, target) >= agsize ||
 	    args->minlen > args->maxlen || args->minlen > agsize ||
 	    args->mod >= args->prod) {
 		args->fsbno = NULLFSBLOCK;
@@ -3281,7 +3282,7 @@ xfs_alloc_vextent_this_ag(
 	if (args->tp->t_highest_agno != NULLAGNUMBER)
 		minimum_agno = args->tp->t_highest_agno;
 
-	error = xfs_alloc_vextent_check_args(args);
+	error = xfs_alloc_vextent_check_args(args, args->fsbno);
 	if (error) {
 		if (error == -ENOSPC)
 			return 0;
@@ -3406,7 +3407,7 @@ xfs_alloc_vextent_start_ag(
 	bool			bump_rotor = false;
 	int			error;
 
-	error = xfs_alloc_vextent_check_args(args);
+	error = xfs_alloc_vextent_check_args(args, args->fsbno);
 	if (error) {
 		if (error == -ENOSPC)
 			return 0;
@@ -3444,25 +3445,29 @@ xfs_alloc_vextent_start_ag(
  * filesystem attempting blocking allocation. This does not wrap or try a second
  * pass, so will not recurse into AGs lower than indicated by fsbno.
  */
-static int
+int
 xfs_alloc_vextent_first_ag(
 	struct xfs_alloc_arg	*args,
-	xfs_agnumber_t		minimum_agno)
-{
+	xfs_fsblock_t		target)
+ {
 	struct xfs_mount	*mp = args->mp;
+	xfs_agnumber_t		minimum_agno = 0;
 	xfs_agnumber_t		start_agno;
 	int			error;
 
-	error = xfs_alloc_vextent_check_args(args);
+	if (args->tp->t_highest_agno != NULLAGNUMBER)
+		minimum_agno = args->tp->t_highest_agno;
+
+	error = xfs_alloc_vextent_check_args(args, target);
 	if (error) {
 		if (error == -ENOSPC)
 			return 0;
 		return error;
 	}
 
-	start_agno = max(minimum_agno, XFS_FSB_TO_AGNO(mp, args->fsbno));
-
+	start_agno = max(minimum_agno, XFS_FSB_TO_AGNO(mp, target));
 	args->type = XFS_ALLOCTYPE_THIS_AG;
+	args->fsbno = target;
 	error =  xfs_alloc_vextent_iterate_ags(args, minimum_agno,
 			start_agno, 0);
 	xfs_alloc_vextent_set_fsbno(args, minimum_agno);
@@ -3495,8 +3500,6 @@ xfs_alloc_vextent(
 		break;
 	case XFS_ALLOCTYPE_START_BNO:
 		return xfs_alloc_vextent_start_ag(args, minimum_agno);
-	case XFS_ALLOCTYPE_FIRST_AG:
-		return xfs_alloc_vextent_first_ag(args, minimum_agno);
 	default:
 		error = -EFSCORRUPTED;
 		ASSERT(0);

fs/xfs/libxfs/xfs_alloc.h

@@ -19,7 +19,6 @@ unsigned int xfs_agfl_size(struct xfs_mount *mp);
 /*
  * Freespace allocation types.  Argument to xfs_alloc_[v]extent.
  */
-#define XFS_ALLOCTYPE_FIRST_AG	0x02	/* ... start at ag 0 */
 #define XFS_ALLOCTYPE_THIS_AG	0x08	/* anywhere in this a.g. */
 #define XFS_ALLOCTYPE_START_BNO	0x10	/* near this block else anywhere */
 #define XFS_ALLOCTYPE_NEAR_BNO	0x20	/* in this a.g. and near this block */
@@ -29,7 +28,6 @@ unsigned int xfs_agfl_size(struct xfs_mount *mp);
 typedef unsigned int xfs_alloctype_t;
 
 #define XFS_ALLOC_TYPES \
-	{ XFS_ALLOCTYPE_FIRST_AG,	"FIRST_AG" }, \
 	{ XFS_ALLOCTYPE_THIS_AG,	"THIS_AG" }, \
 	{ XFS_ALLOCTYPE_START_BNO,	"START_BNO" }, \
 	{ XFS_ALLOCTYPE_NEAR_BNO,	"NEAR_BNO" }, \
@@ -130,6 +128,14 @@ xfs_alloc_vextent(
  */
 int xfs_alloc_vextent_this_ag(struct xfs_alloc_arg *args);
 
+/*
+ * Iterate from the AG indicated from args->fsbno through to the end of the
+ * filesystem attempting blocking allocation. This is for use in last
+ * resort allocation attempts when everything else has failed.
+ */
+int xfs_alloc_vextent_first_ag(struct xfs_alloc_arg *args,
+		xfs_fsblock_t target);
+
 /*
  * Free an extent.
  */

fs/xfs/libxfs/xfs_bmap.c

@@ -3248,13 +3248,6 @@ xfs_bmap_btalloc_filestreams(
 	int			notinit = 0;
 	int			error;
 
-	if (ap->tp->t_flags & XFS_TRANS_LOWMODE) {
-		args->type = XFS_ALLOCTYPE_FIRST_AG;
-		args->total = ap->minlen;
-		args->minlen = ap->minlen;
-		return 0;
-	}
-
 	args->type = XFS_ALLOCTYPE_NEAR_BNO;
 	args->total = ap->total;
 
@@ -3462,9 +3455,7 @@ xfs_bmap_exact_minlen_extent_alloc(
 	 */
 	ap->blkno = XFS_AGB_TO_FSB(mp, 0, 0);
 
-	args.fsbno = ap->blkno;
 	args.oinfo = XFS_RMAP_OINFO_SKIP_UPDATE;
-	args.type = XFS_ALLOCTYPE_FIRST_AG;
 	args.minlen = args.maxlen = ap->minlen;
 	args.total = ap->total;
 
@@ -3476,7 +3467,7 @@ xfs_bmap_exact_minlen_extent_alloc(
 	args.resv = XFS_AG_RESV_NONE;
 	args.datatype = ap->datatype;
 
-	error = xfs_alloc_vextent(&args);
+	error = xfs_alloc_vextent_first_ag(&args, ap->blkno);
 	if (error)
 		return error;
 
@@ -3623,10 +3614,21 @@ xfs_bmap_btalloc_best_length(
 	 * size to the largest space found.
 	 */
 	if ((ap->datatype & XFS_ALLOC_USERDATA) &&
-	    xfs_inode_is_filestream(ap->ip))
+	    xfs_inode_is_filestream(ap->ip)) {
+		/*
+		 * 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 (ap->tp->t_flags & XFS_TRANS_LOWMODE) {
+			args->minlen = ap->minlen;
+			goto critically_low_space;
+		}
 		error = xfs_bmap_btalloc_filestreams(ap, args, &blen);
-	else
+	} else {
 		error = xfs_bmap_btalloc_select_lengths(ap, args, &blen);
+	}
 	if (error)
 		return error;
 
@@ -3673,10 +3675,9 @@ xfs_bmap_btalloc_best_length(
 	 * so they don't waste time on allocation modes that are unlikely to
 	 * succeed.
 	 */
-	args->fsbno = 0;
-	args->type = XFS_ALLOCTYPE_FIRST_AG;
+critically_low_space:
 	args->total = ap->minlen;
-	error = xfs_alloc_vextent(args);
+	error = xfs_alloc_vextent_first_ag(args, 0);
 	if (error)
 		return error;
 	ap->tp->t_flags |= XFS_TRANS_LOWMODE;