f2fs: fix to avoid potential deadlock

We should always check F2FS_I(inode)->cp_task condition in prior to other
conditions in __should_serialize_io() to avoid deadloop described in
commit 040d2bb3 ("f2fs: fix to avoid deadloop if data_flush is on"),
however we break this rule when we support compression, fix it.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -2962,15 +2962,17 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
 static inline bool __should_serialize_io(struct inode *inode,
 					struct writeback_control *wbc)
 {
+	/* to avoid deadlock in path of data flush */
+	if (F2FS_I(inode)->cp_task)
+		return false;
+
 	if (!S_ISREG(inode->i_mode))
 		return false;
-	if (f2fs_compressed_file(inode))
-		return true;
 	if (IS_NOQUOTA(inode))
 		return false;
-	/* to avoid deadlock in path of data flush */
-	if (F2FS_I(inode)->cp_task)
-		return false;
+
+	if (f2fs_compressed_file(inode))
+		return true;
 	if (wbc->sync_mode != WB_SYNC_ALL)
 		return true;
 	if (get_dirty_pages(inode) >= SM_I(F2FS_I_SB(inode))->min_seq_blocks)