f2fs: rebuild sit page from sit info in mem

This patch rebuild sit page from sit info in mem instead
of issue a read io.

I test this method and the result is as below:

Pre:
 mmc_perf_test-12061 [001] ...1   976.819992: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [001] ...1   976.856446: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [003] ...1   998.976946: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [003] ...1   999.023269: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [003] ...1  1022.060772: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [003] ...1  1022.111034: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [002] ...1  1070.127643: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [003] ...1  1070.187352: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [003] ...1  1095.942124: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [003] ...1  1095.995975: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [003] ...1  1122.535091: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [003] ...1  1122.586521: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [001] ...1  1147.897487: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [001] ...1  1147.959438: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [003] ...1  1177.926951: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [002] ...1  1177.976823: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
 mmc_perf_test-12061 [002] ...1  1204.176087: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
 mmc_perf_test-12061 [002] ...1  1204.239046: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit

Some sit flush consume more than 50ms.

Now:
mmc_perf_test-2187  [007] ...1   196.840684: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [007] ...1   196.841258: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [007] ...1   219.430582: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [007] ...1   219.431144: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [002] ...1   243.638678: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [000] ...1   243.638980: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [002] ...1   265.392180: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [002] ...1   265.392245: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [000] ...1   290.309051: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [000] ...1   290.309116: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [003] ...1   317.144209: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [003] ...1   317.145913: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [005] ...1   343.224954: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [005] ...1   343.225574: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [000] ...1   370.239846: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [000] ...1   370.241138: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [001] ...1   397.029043: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [001] ...1   397.030750: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit
mmc_perf_test-2187  [003] ...1   425.386377: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = start flush sit
mmc_perf_test-2187  [003] ...1   425.387735: f2fs_write_checkpoint: dev = (259,44), checkpoint for Sync, state = end flush sit

Most sit flush consume no more than 1ms.
Signed-off-by: NYunlei He <heyunlei@huawei.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -3110,28 +3110,19 @@ static struct page *get_next_sit_page(struct f2fs_sb_info *sbi,
 					unsigned int start)
 {
 	struct sit_info *sit_i = SIT_I(sbi);
-	struct page *src_page, *dst_page;
+	struct page *page;
 	pgoff_t src_off, dst_off;
-	void *src_addr, *dst_addr;
 
 	src_off = current_sit_addr(sbi, start);
 	dst_off = next_sit_addr(sbi, src_off);
 
-	/* get current sit block page without lock */
-	src_page = get_meta_page(sbi, src_off);
-	dst_page = grab_meta_page(sbi, dst_off);
-	f2fs_bug_on(sbi, PageDirty(src_page));
-
-	src_addr = page_address(src_page);
-	dst_addr = page_address(dst_page);
-	memcpy(dst_addr, src_addr, PAGE_SIZE);
-
-	set_page_dirty(dst_page);
-	f2fs_put_page(src_page, 1);
+	page = grab_meta_page(sbi, dst_off);
+	seg_info_to_sit_page(sbi, page, start);
 
+	set_page_dirty(page);
 	set_to_next_sit(sit_i, start);
 
-	return dst_page;
+	return page;
 }
 
 static struct sit_entry_set *grab_sit_entry_set(void)

fs/f2fs/segment.h

@@ -348,16 +348,41 @@ static inline void seg_info_from_raw_sit(struct seg_entry *se,
 	se->mtime = le64_to_cpu(rs->mtime);
 }
 
-static inline void seg_info_to_raw_sit(struct seg_entry *se,
+static inline void __seg_info_to_raw_sit(struct seg_entry *se,
 					struct f2fs_sit_entry *rs)
 {
 	unsigned short raw_vblocks = (se->type << SIT_VBLOCKS_SHIFT) |
 					se->valid_blocks;
 	rs->vblocks = cpu_to_le16(raw_vblocks);
 	memcpy(rs->valid_map, se->cur_valid_map, SIT_VBLOCK_MAP_SIZE);
+	rs->mtime = cpu_to_le64(se->mtime);
+}
+
+static inline void seg_info_to_sit_page(struct f2fs_sb_info *sbi,
+				struct page *page, unsigned int start)
+{
+	struct f2fs_sit_block *raw_sit;
+	struct seg_entry *se;
+	struct f2fs_sit_entry *rs;
+	unsigned int end = min(start + SIT_ENTRY_PER_BLOCK,
+					(unsigned long)MAIN_SEGS(sbi));
+	int i;
+
+	raw_sit = (struct f2fs_sit_block *)page_address(page);
+	for (i = 0; i < end - start; i++) {
+		rs = &raw_sit->entries[i];
+		se = get_seg_entry(sbi, start + i);
+		__seg_info_to_raw_sit(se, rs);
+	}
+}
+
+static inline void seg_info_to_raw_sit(struct seg_entry *se,
+					struct f2fs_sit_entry *rs)
+{
+	__seg_info_to_raw_sit(se, rs);
+
 	memcpy(se->ckpt_valid_map, rs->valid_map, SIT_VBLOCK_MAP_SIZE);
 	se->ckpt_valid_blocks = se->valid_blocks;
-	rs->mtime = cpu_to_le64(se->mtime);
 }
 
 static inline unsigned int find_next_inuse(struct free_segmap_info *free_i,