f2fs: introduce inmem curseg

Previous implementation of aligned pinfile allocation will:
- allocate new segment on cold data log no matter whether last used
segment is partially used or not, it makes IOs more random;
- force concurrent cold data/GCed IO going into warm data area, it
can make a bad effect on hot/cold data separation;

In this patch, we introduce a new type of log named 'inmem curseg',
the differents from normal curseg is:
- it reuses existed segment type (CURSEG_XXX_NODE/DATA);
- it only exists in memory, its segno, blkofs, summary will not b
 persisted into checkpoint area;

With this new feature, we can enhance scalability of log, special
allocators can be created for purposes:
- pure lfs allocator for aligned pinfile allocation or file
defragmentation
- pure ssr allocator for later feature

So that, let's update aligned pinfile allocation to use this new
inmem curseg fwk.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 4276c0f..41a91aa 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -164,7 +164,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
 		* 100 / (int)(sbi->user_block_count >> sbi->log_blocks_per_seg)
 		/ 2;
 	si->util_invalid = 50 - si->util_free - si->util_valid;
-	for (i = CURSEG_HOT_DATA; i <= CURSEG_COLD_NODE; i++) {
+	for (i = CURSEG_HOT_DATA; i < NO_CHECK_TYPE; i++) {
 		struct curseg_info *curseg = CURSEG_I(sbi, i);
 		si->curseg[i] = curseg->segno;
 		si->cursec[i] = GET_SEC_FROM_SEG(sbi, curseg->segno);
@@ -393,6 +393,10 @@ static int stat_show(struct seq_file *s, void *v)
 			   si->dirty_seg[CURSEG_COLD_NODE],
 			   si->full_seg[CURSEG_COLD_NODE],
 			   si->valid_blks[CURSEG_COLD_NODE]);
+		seq_printf(s, "  - Pinned file: %8d %8d %8d\n",
+			   si->curseg[CURSEG_COLD_DATA_PINNED],
+			   si->cursec[CURSEG_COLD_DATA_PINNED],
+			   si->curzone[CURSEG_COLD_DATA_PINNED]);
 		seq_printf(s, "\n  - Valid: %d\n  - Dirty: %d\n",
 			   si->main_area_segs - si->dirty_count -
 			   si->prefree_count - si->free_segs,