f2fs: use PGP_LOCK to check its truncation

Previously, after trylock_page is succeeded, it doesn't check its mapping.
In order to fix that, we can just give PGP_LOCK to pagecache_get_page.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -1202,13 +1202,10 @@ static void flush_inline_data(struct f2fs_sb_info *sbi, nid_t ino)
 	if (!inode)
 		return;
 
-	page = pagecache_get_page(inode->i_mapping, 0, FGP_NOWAIT, 0);
+	page = pagecache_get_page(inode->i_mapping, 0, FGP_LOCK|FGP_NOWAIT, 0);
 	if (!page)
 		goto iput_out;
 
-	if (!trylock_page(page))
-		goto release_out;
-
 	if (!PageUptodate(page))
 		goto page_out;
 
@@ -1223,9 +1220,7 @@ static void flush_inline_data(struct f2fs_sb_info *sbi, nid_t ino)
 	else
 		set_page_dirty(page);
 page_out:
-	unlock_page(page);
-release_out:
-	f2fs_put_page(page, 0);
+	f2fs_put_page(page, 1);
 iput_out:
 	iput(inode);
 }