f2fs: clear radix tree dirty tag of pages whose dirty flag is cleared

On a senario like writing out the first dirty page of the inode
as the inline data, we only cleared dirty flags of the pages, but
didn't clear the dirty tags of those pages in the radix tree.

If we don't clear the dirty tags of the pages in the radix tree, the
inodes which contain the pages will be marked with I_DIRTY_PAGES again
and again, and writepages() for the inodes will be invoked in every
writeback period. As a result, nothing will be done in every
writepages() for the inodes and it will just consume CPU time
meaninglessly.

Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 37f9c7f..c0c933ad 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -705,6 +705,8 @@
 	struct	f2fs_dentry_block *dentry_blk;
 	unsigned int bit_pos;
 	int slots = GET_DENTRY_SLOTS(le16_to_cpu(dentry->name_len));
+	struct address_space *mapping = page_mapping(page);
+	unsigned long flags;
 	int i;
 
 	f2fs_update_time(F2FS_I_SB(dir), REQ_TIME);
@@ -735,6 +737,11 @@
 
 	if (bit_pos == NR_DENTRY_IN_BLOCK &&
 			!truncate_hole(dir, page->index, page->index + 1)) {
+		spin_lock_irqsave(&mapping->tree_lock, flags);
+		radix_tree_tag_clear(&mapping->page_tree, page_index(page),
+				     PAGECACHE_TAG_DIRTY);
+		spin_unlock_irqrestore(&mapping->tree_lock, flags);
+
 		clear_page_dirty_for_io(page);
 		ClearPagePrivate(page);
 		ClearPageUptodate(page);