f2fs: allocate remained free segments in the LFS mode

This patch adds a new condition that allocates free segments in the current
active section even if SSR is needed.
Otherwise, f2fs cannot allocate remained free segments in the section since
SSR finds dirty segments only.

Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/segment.c

@@ -347,6 +347,17 @@ next:
 	return NULL_SEGNO;
 }
 
+static int is_next_segment_free(struct f2fs_sb_info *sbi, int type)
+{
+	struct curseg_info *curseg = CURSEG_I(sbi, type);
+	unsigned int segno = curseg->segno;
+	struct free_segmap_info *free_i = FREE_I(sbi);
+
+	if (segno + 1 < TOTAL_SEGS(sbi) && (segno + 1) % sbi->segs_per_sec)
+		return !test_bit(segno + 1, free_i->free_segmap);
+	return 0;
+}
+
 /*
  * Find a new segment from the free segments bitmap to right order
  * This function should be returned with success, otherwise BUG
@@ -580,6 +591,8 @@ static void allocate_segment_by_default(struct f2fs_sb_info *sbi,
 		change_curseg(sbi, type, false);
 	else if (type == CURSEG_WARM_NODE)
 		new_curseg(sbi, type, false);
+	else if (curseg->alloc_type == LFS && is_next_segment_free(sbi, type))
+		new_curseg(sbi, type, false);
 	else if (need_SSR(sbi) && get_ssr_segment(sbi, type))
 		change_curseg(sbi, type, true);
 	else