f2fs: don't keep meta pages used for block migration

For migration of encrypted inode's block, we load data of encrypted block
into meta inode's page cache, after checkpoint, those all intermediate
pages should be clean, and no one will read them again, so let's just
release them for more memory.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -1408,6 +1408,14 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	commit_checkpoint(sbi, ckpt, start_blk);
 	wait_on_all_pages_writeback(sbi);
 
+	/*
+	 * invalidate intermediate page cache borrowed from meta inode
+	 * which are used for migration of encrypted inode's blocks.
+	 */
+	if (f2fs_sb_has_encrypt(sbi->sb))
+		invalidate_mapping_pages(META_MAPPING(sbi),
+				MAIN_BLKADDR(sbi), MAX_BLKADDR(sbi) - 1);
+
 	f2fs_release_ino_entry(sbi, false);
 
 	clear_sbi_flag(sbi, SBI_IS_DIRTY);