[Cluster-devel] [PATCHv3 dlm/next 14/20] fs: dlm: remove unaligned memory access handling

[Alexander Aring <aahringo@redhat.com>]

This patch removes unaligned memory access handling for receiving
midcomms messages. This handling will not fix the unaligned memory
access in general. All messages should be length aligned to 8 bytes,
there exists cases where this isn't the case. It's part of the sending
handling to not send such messages. As the sending handling itself, with
the internal allocator of page buffers, can occur in unaligned memory
access of dlm message fields we just ignore that problem for now as it
seems this code is used by architecture which can handle it.

This patch adds a comment to take care about that problem in a major
bump of dlm protocol.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/midcomms.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
index e058e017c77d..45dd3d7d857f 100644
--- a/fs/dlm/midcomms.c
+++ b/fs/dlm/midcomms.c
@@ -22,8 +22,6 @@
  * into packets and sends them to the comms layer.
  */
 
-#include <asm/unaligned.h>
-
 #include "dlm_internal.h"
 #include "lowcomms.h"
 #include "config.h"
@@ -93,13 +91,22 @@ int dlm_process_incoming_buffer(int nodeid, unsigned char *buf, int len)
 	while (len >= sizeof(struct dlm_header)) {
 		hd = (struct dlm_header *)ptr;
 
-		/* no message should be more than this otherwise we
-		 * cannot deliver this message to upper layers
+		/* no message should be more than DEFAULT_BUFFER_SIZE or
+		 * less than dlm_header size.
+		 *
+		 * Some messages does not have a 8 byte length boundary yet
+		 * which can occur in a unaligned memory access of some dlm
+		 * messages. However this problem need to be fixed at the
+		 * sending side, for now it seems nobody run into architecture
+		 * related issues yet but it slows down some processing.
+		 * Fixing this issue should be scheduled in future by doing
+		 * the next major version bump.
 		 */
-		msglen = get_unaligned_le16(&hd->h_length);
-		if (msglen > DEFAULT_BUFFER_SIZE) {
-			log_print("received invalid length header: %u, will abort message parsing",
-				  msglen);
+		msglen = le16_to_cpu(hd->h_length);
+		if (msglen > DEFAULT_BUFFER_SIZE ||
+		    msglen < sizeof(struct dlm_header)) {
+			log_print("received invalid length header: %u from node %d, will abort message parsing",
+				  msglen, nodeid);
 			return -EBADMSG;
 		}
 
@@ -132,14 +139,6 @@ int dlm_process_incoming_buffer(int nodeid, unsigned char *buf, int len)
 			goto skip;
 		}
 
-		/* for aligned memory access, we just copy current message
-		 * to begin of the buffer which contains already parsed buffer
-		 * data and should provide align access for upper layers
-		 * because the start address of the buffer has a aligned
-		 * address. This memmove can be removed when the upperlayer
-		 * is capable of unaligned memory access.
-		 */
-		memmove(buf, ptr, msglen);
 		dlm_receive_buffer((union dlm_packet *)buf, nodeid);
 
 skip:
-- 
2.26.2