f2fs: allocate node and hot data in the beginning of partition

In order to give more spatial locality, this patch changes the block allocation
policy which assigns beginning of partition for small and hot data/node blocks.
In order to do this, we set noheap allocation by default and introduce another
mount option, heap, to reset it back.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -172,7 +172,11 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
 	if (gc_type != FG_GC && p->max_search > sbi->max_victim_search)
 		p->max_search = sbi->max_victim_search;
 
-	p->offset = sbi->last_victim[p->gc_mode];
+	/* let's select beginning hot/small space first */
+	if (type == CURSEG_HOT_DATA || IS_NODESEG(type))
+		p->offset = 0;
+	else
+		p->offset = sbi->last_victim[p->gc_mode];
 }
 
 static unsigned int get_max_cost(struct f2fs_sb_info *sbi,

fs/f2fs/segment.c

@@ -1519,6 +1519,14 @@ static void reset_curseg(struct f2fs_sb_info *sbi, int type, int modified)
 	__set_sit_entry_type(sbi, type, curseg->segno, modified);
 }
 
+static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)
+{
+	if (type == CURSEG_HOT_DATA || IS_NODESEG(type))
+		return 0;
+
+	return CURSEG_I(sbi, type)->segno;
+}
+
 /*
  * Allocate a current working segment.
  * This function always allocates a free segment in LFS manner.
@@ -1537,6 +1545,7 @@ static void new_curseg(struct f2fs_sb_info *sbi, int type, bool new_sec)
 	if (test_opt(sbi, NOHEAP))
 		dir = ALLOC_RIGHT;
 
+	segno = __get_next_segno(sbi, type);
 	get_new_segment(sbi, &segno, new_sec, dir);
 	curseg->next_segno = segno;
 	reset_curseg(sbi, type, 1);

fs/f2fs/super.c

@@ -83,6 +83,7 @@ enum {
 	Opt_discard,
 	Opt_nodiscard,
 	Opt_noheap,
+	Opt_heap,
 	Opt_user_xattr,
 	Opt_nouser_xattr,
 	Opt_acl,
@@ -117,6 +118,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_discard, "discard"},
 	{Opt_nodiscard, "nodiscard"},
 	{Opt_noheap, "no_heap"},
+	{Opt_heap, "heap"},
 	{Opt_user_xattr, "user_xattr"},
 	{Opt_nouser_xattr, "nouser_xattr"},
 	{Opt_acl, "acl"},
@@ -437,6 +439,9 @@ static int parse_options(struct super_block *sb, char *options)
 		case Opt_noheap:
 			set_opt(sbi, NOHEAP);
 			break;
+		case Opt_heap:
+			clear_opt(sbi, NOHEAP);
+			break;
 #ifdef CONFIG_F2FS_FS_XATTR
 		case Opt_user_xattr:
 			set_opt(sbi, XATTR_USER);
@@ -914,7 +919,9 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 	if (test_opt(sbi, DISCARD))
 		seq_puts(seq, ",discard");
 	if (test_opt(sbi, NOHEAP))
-		seq_puts(seq, ",no_heap_alloc");
+		seq_puts(seq, ",no_heap");
+	else
+		seq_puts(seq, ",heap");
 #ifdef CONFIG_F2FS_FS_XATTR
 	if (test_opt(sbi, XATTR_USER))
 		seq_puts(seq, ",user_xattr");
@@ -1047,6 +1054,7 @@ static void default_options(struct f2fs_sb_info *sbi)
 	set_opt(sbi, INLINE_DATA);
 	set_opt(sbi, INLINE_DENTRY);
 	set_opt(sbi, EXTENT_CACHE);
+	set_opt(sbi, NOHEAP);
 	sbi->sb->s_flags |= MS_LAZYTIME;
 	set_opt(sbi, FLUSH_MERGE);
 	if (f2fs_sb_mounted_blkzoned(sbi->sb)) {