f2fs: compress: fix to avoid memory leak on cc->cpages

Memory allocated for storing compressed pages' poitner should be
released after f2fs_write_compressed_pages(), otherwise it will
cause memory leak issue.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Fixes: 4c8ff709 ("f2fs: support data compression")
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/compress.c

@@ -1385,6 +1385,8 @@ int f2fs_write_multi_pages(struct compress_ctx *cc,
 		err = f2fs_write_compressed_pages(cc, submitted,
 							wbc, io_type);
 		cops->destroy_compress_ctx(cc);
+		kfree(cc->cpages);
+		cc->cpages = NULL;
 		if (!err)
 			return 0;
 		f2fs_bug_on(F2FS_I_SB(cc->inode), err != -EAGAIN);