f2fs: fix to avoid potential deadlock

Using f2fs_trylock_op() in f2fs_write_compressed_pages() to avoid potential
deadlock like we did in f2fs_write_single_data_page().
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/compress.c

@@ -775,7 +775,6 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
 		.encrypted_page = NULL,
 		.compressed_page = NULL,
 		.submitted = false,
-		.need_lock = LOCK_RETRY,
 		.io_type = io_type,
 		.io_wbc = wbc,
 		.encrypted = f2fs_encrypted_file(cc->inode),
@@ -788,9 +787,10 @@ static int f2fs_write_compressed_pages(struct compress_ctx *cc,
 	loff_t psize;
 	int i, err;
 
-	set_new_dnode(&dn, cc->inode, NULL, NULL, 0);
+	if (!f2fs_trylock_op(sbi))
+		return -EAGAIN;
 
-	f2fs_lock_op(sbi);
+	set_new_dnode(&dn, cc->inode, NULL, NULL, 0);
 
 	err = f2fs_get_dnode_of_data(&dn, start_idx, LOOKUP_NODE);
 	if (err)