xfs: get rid of notinit from xfs_bmap_longest_free_extent

It is only set if reading the AGF gets a EAGAIN error. Just return
the EAGAIN error and handle that error in the callers.

This means we can remove the not_init parameter from
xfs_bmap_select_minlen(), too, because the use of not_init there is
pessimistic. If we can't read the agf, it won't increase blen.

The only time we actually care whether we checked all the AGFs for
contiguous free space is when the best length is less than the
minimum allocation length. If not_init is set, then we ignore blen
and set the minimum alloc length to the absolute minimum, not the
best length we know already is present.

However, if blen is less than the minimum we're going to ignore it
anyway, regardless of whether we scanned all the AGFs or not.  Hence
not_init can go away, because we only use if blen is good from
the scanned AGs otherwise we ignore it altogether and use minlen.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/libxfs/xfs_bmap.c

@@ -3139,8 +3139,7 @@ static int
 xfs_bmap_longest_free_extent(
 	struct xfs_perag	*pag,
 	struct xfs_trans	*tp,
-	xfs_extlen_t		*blen,
-	int			*notinit)
+	xfs_extlen_t		*blen)
 {
 	xfs_extlen_t		longest;
 	int			error = 0;
@@ -3148,14 +3147,8 @@ xfs_bmap_longest_free_extent(
 	if (!xfs_perag_initialised_agf(pag)) {
 		error = xfs_alloc_read_agf(pag, tp, XFS_ALLOC_FLAG_TRYLOCK,
 				NULL);
-		if (error) {
-			/* Couldn't lock the AGF, so skip this AG. */
-			if (error == -EAGAIN) {
-				*notinit = 1;
-				error = 0;
-			}
+		if (error)
 			return error;
-		}
 	}
 
 	longest = xfs_alloc_longest_free_extent(pag,
@@ -3167,32 +3160,28 @@ xfs_bmap_longest_free_extent(
 	return 0;
 }
 
-static void
+static xfs_extlen_t
 xfs_bmap_select_minlen(
 	struct xfs_bmalloca	*ap,
 	struct xfs_alloc_arg	*args,
-	xfs_extlen_t		*blen,
-	int			notinit)
+	xfs_extlen_t		blen)
 {
-	if (notinit || *blen < ap->minlen) {
-		/*
-		 * Since we did a BUF_TRYLOCK above, it is possible that
-		 * there is space for this request.
-		 */
-		args->minlen = ap->minlen;
-	} else if (*blen < args->maxlen) {
-		/*
-		 * If the best seen length is less than the request length,
-		 * use the best as the minimum.
-		 */
-		args->minlen = *blen;
-	} else {
-		/*
-		 * Otherwise we've seen an extent as big as maxlen, use that
-		 * as the minimum.
-		 */
-		args->minlen = args->maxlen;
-	}
+
+	/*
+	 * Since we used XFS_ALLOC_FLAG_TRYLOCK in _longest_free_extent(), it is
+	 * possible that there is enough contiguous free space for this request.
+	 */
+	if (blen < ap->minlen)
+		return ap->minlen;
+
+	/*
+	 * If the best seen length is less than the request length,
+	 * use the best as the minimum, otherwise we've got the maxlen we
+	 * were asked for.
+	 */
+	if (blen < args->maxlen)
+		return blen;
+	return args->maxlen;
 }
 
 static int
@@ -3204,7 +3193,6 @@ xfs_bmap_btalloc_select_lengths(
 	struct xfs_mount	*mp = args->mp;
 	struct xfs_perag	*pag;
 	xfs_agnumber_t		agno, startag;
-	int			notinit = 0;
 	int			error = 0;
 
 	if (ap->tp->t_flags & XFS_TRANS_LOWMODE) {
@@ -3220,17 +3208,17 @@ xfs_bmap_btalloc_select_lengths(
 
 	*blen = 0;
 	for_each_perag_wrap(mp, startag, agno, pag) {
-		error = xfs_bmap_longest_free_extent(pag, args->tp, blen,
-						     &notinit);
-		if (error)
+		error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
+		if (error && error != -EAGAIN)
 			break;
+		error = 0;
 		if (*blen >= args->maxlen)
 			break;
 	}
 	if (pag)
 		xfs_perag_rele(pag);
 
-	xfs_bmap_select_minlen(ap, args, blen, notinit);
+	args->minlen = xfs_bmap_select_minlen(ap, args, *blen);
 	return error;
 }
 
@@ -3243,7 +3231,6 @@ xfs_bmap_btalloc_filestreams_select_lengths(
 	struct xfs_mount	*mp = ap->ip->i_mount;
 	struct xfs_perag	*pag;
 	xfs_agnumber_t		start_agno;
-	int			notinit = 0;
 	int			error;
 
 	args->total = ap->total;
@@ -3254,11 +3241,13 @@ xfs_bmap_btalloc_filestreams_select_lengths(
 
 	pag = xfs_perag_grab(mp, start_agno);
 	if (pag) {
-		error = xfs_bmap_longest_free_extent(pag, args->tp, blen,
-				&notinit);
+		error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
 		xfs_perag_rele(pag);
-		if (error)
-			return error;
+		if (error) {
+			if (error != -EAGAIN)
+				return error;
+			*blen = 0;
+		}
 	}
 
 	if (*blen < args->maxlen) {
@@ -3274,18 +3263,18 @@ xfs_bmap_btalloc_filestreams_select_lengths(
 		if (!pag)
 			goto out_select;
 
-		error = xfs_bmap_longest_free_extent(pag, args->tp,
-				blen, &notinit);
+		error = xfs_bmap_longest_free_extent(pag, args->tp, blen);
 		xfs_perag_rele(pag);
-		if (error)
-			return error;
-
+		if (error) {
+			if (error != -EAGAIN)
+				return error;
+			*blen = 0;
+		}
 		start_agno = agno;
-
 	}
 
 out_select:
-	xfs_bmap_select_minlen(ap, args, blen, notinit);
+	args->minlen = xfs_bmap_select_minlen(ap, args, *blen);
 
 	/*
 	 * Set the failure fallback case to look in the selected AG as stream