[PATCH 8/9] f2fs: avoid race for summary information

[Jaegeuk Kim <jaegeuk.kim@samsung.com>]

In order to do GC more reliably, I'd like to lock the vicitm summary page
until its GC is completed, and also prevent any checkpoint process.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
---
 fs/f2fs/gc.c    | 8 +-------
 fs/f2fs/node.c  | 2 +-
 fs/f2fs/super.c | 7 +++++--
 3 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 54aceb2..54ac13d 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -641,12 +641,6 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 	if (IS_ERR(sum_page))
 		return;
 
-	/*
-	 * CP needs to lock sum_page. In this time, we don't need
-	 * to lock this page, because this summary page is not gone anywhere.
-	 * Also, this page is not gonna be updated before GC is done.
-	 */
-	unlock_page(sum_page);
 	sum = page_address(sum_page);
 
 	switch (GET_SUM_TYPE((&sum->footer))) {
@@ -660,7 +654,7 @@ static void do_garbage_collect(struct f2fs_sb_info *sbi, unsigned int segno,
 	stat_inc_seg_count(sbi, GET_SUM_TYPE((&sum->footer)));
 	stat_inc_call_count(sbi->stat_info);
 
-	f2fs_put_page(sum_page, 0);
+	f2fs_put_page(sum_page, 1);
 }
 
 int f2fs_gc(struct f2fs_sb_info *sbi)
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index c5360b7..7555fb7 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1148,7 +1148,7 @@ static int f2fs_write_node_pages(struct address_space *mapping,
 
 	/* First check balancing cached NAT entries */
 	if (try_to_free_nats(sbi, NAT_ENTRY_PER_BLOCK)) {
-		write_checkpoint(sbi, false);
+		f2fs_sync_fs(sbi->sb, true);
 		return 0;
 	}
 
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index ea325c8..161e6c6 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -137,10 +137,13 @@ int f2fs_sync_fs(struct super_block *sb, int sync)
 	if (!sbi->s_dirty && !get_pages(sbi, F2FS_DIRTY_NODES))
 		return 0;
 
-	if (sync)
+	if (sync) {
+		mutex_lock(&sbi->gc_mutex);
 		write_checkpoint(sbi, false);
-	else
+		mutex_unlock(&sbi->gc_mutex);
+	} else {
 		f2fs_balance_fs(sbi);
+	}
 
 	return 0;
 }
-- 
1.8.1.3.566.gaa39828