xfs: streamline xfs_filestream_pick_ag

Directly return the error from xfs_bmap_longest_free_extent instead
of breaking from the loop and handling it there, and use a done
label to directly jump to the exist when we found a suitable perag
structure to reduce the indentation level and pag/max_pag check
complexity in the tail of the function.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
Signed-off-by: Carlos Maiolino <[e-mail]>

fs/xfs/xfs_filestream.c

···
 	xfs_extlen_t		minfree, maxfree = 0;
 	xfs_agnumber_t		agno;
 	bool			first_pass = true;
-	int			err;
 
 	/* 2% of an AG's blocks must be free for it to be chosen. */
 	minfree = mp->m_sb.sb_agblocks / 50;
 
 restart:
 	for_each_perag_wrap(mp, start_agno, agno, pag) {
+		int		err;
+
 		trace_xfs_filestream_scan(pag, pino);
+
 		*longest = 0;
 		err = xfs_bmap_longest_free_extent(pag, NULL, longest);
 		if (err) {
-			if (err != -EAGAIN)
-				break;
-			/* Couldn't lock the AGF, skip this AG. */
-			err = 0;
-			continue;
+			if (err == -EAGAIN) {
+				/* Couldn't lock the AGF, skip this AG. */
+				err = 0;
+				continue;
+			}
+			xfs_perag_rele(pag);
+			if (max_pag)
+				xfs_perag_rele(max_pag);
+			return err;
 		}
 
 		/* Keep track of the AG with the most free blocks. */
···
 			     !(flags & XFS_PICK_USERDATA) ||
 			     (flags & XFS_PICK_LOWSPACE))) {
 				/* Break out, retaining the reference on the AG. */
-				break;
+				if (max_pag)
+					xfs_perag_rele(max_pag);
+				goto done;
 			}
 		}
 
···
 		atomic_dec(&pag->pagf_fstrms);
 	}
 
-	if (err) {
-		xfs_perag_rele(pag);
-		if (max_pag)
-			xfs_perag_rele(max_pag);
-		return err;
+	/*
+	 * Allow a second pass to give xfs_bmap_longest_free_extent() another
+	 * attempt at locking AGFs that it might have skipped over before we
+	 * fail.
+	 */
+	if (first_pass) {
+		first_pass = false;
+		goto restart;
 	}
 
-	if (!pag) {
-		/*
-		 * Allow a second pass to give xfs_bmap_longest_free_extent()
-		 * another attempt at locking AGFs that it might have skipped
-		 * over before we fail.
-		 */
-		if (first_pass) {
-			first_pass = false;
-			goto restart;
-		}
-
-		/*
-		 * We must be low on data space, so run a final lowspace
-		 * optimised selection pass if we haven't already.
-		 */
-		if (!(flags & XFS_PICK_LOWSPACE)) {
-			flags |= XFS_PICK_LOWSPACE;
-			goto restart;
-		}
-
-		/*
-		 * No unassociated AGs are available, so select the AG with the
-		 * most free space, regardless of whether it's already in use by
-		 * another filestream. It none suit, just use whatever AG we can
-		 * grab.
-		 */
-		if (!max_pag) {
-			for_each_perag_wrap(args->mp, 0, start_agno, pag) {
-				max_pag = pag;
-				break;
-			}
-
-			/* Bail if there are no AGs at all to select from. */
-			if (!max_pag)
-				return -ENOSPC;
-		}
-
-		pag = max_pag;
-		atomic_inc(&pag->pagf_fstrms);
-	} else if (max_pag) {
-		xfs_perag_rele(max_pag);
+	/*
+	 * We must be low on data space, so run a final lowspace optimised
+	 * selection pass if we haven't already.
+	 */
+	if (!(flags & XFS_PICK_LOWSPACE)) {
+		flags |= XFS_PICK_LOWSPACE;
+		goto restart;
 	}
 
+	/*
+	 * No unassociated AGs are available, so select the AG with the most
+	 * free space, regardless of whether it's already in use by another
+	 * filestream. It none suit, just use whatever AG we can grab.
+	 */
+	if (!max_pag) {
+		for_each_perag_wrap(args->mp, 0, start_agno, pag) {
+			max_pag = pag;
+			break;
+		}
+
+		/* Bail if there are no AGs at all to select from. */
+		if (!max_pag)
+			return -ENOSPC;
+	}
+
+	pag = max_pag;
+	atomic_inc(&pag->pagf_fstrms);
+done:
 	trace_xfs_filestream_pick(pag, pino);
 	args->pag = pag;
 	return 0;