xfs: fix unaligned access in readdir

This patch should fix the issue seen on Alpha with unaligned accesses
in the new readdir code. By aligning each dirent to sizeof(u64) we'll
avoid unaligned accesses. To make doubly sure we're not hitting problems also rearrange struct hack_dirent to avoid holes.

Signed-off-by Christoph Hellwig <[email protected]>

Index: linux-2.6-xfs/fs/xfs/linux-2.6/xfs_file.c
===================================================================

fs/xfs/linux-2.6/xfs_file.c +10 -6

@@ -262,9 +262,9 @@ xfs_file_readdir(
 #else
 
 struct hack_dirent {
-	int		namlen;
-	loff_t		offset;
 	u64		ino;
+	loff_t		offset;
+	int		namlen;
 	unsigned int	d_type;
 	char		name[];
 };

@@ -286,8 +286,10 @@ xfs_hack_filldir(
 {
 	struct hack_callback *buf = __buf;
 	struct hack_dirent *de = (struct hack_dirent *)(buf->dirent + buf->used);
+	unsigned int reclen;
 
-	if (buf->used + sizeof(struct hack_dirent) + namlen > buf->len)
+	reclen = ALIGN(sizeof(struct hack_dirent) + namlen, sizeof(u64));
+	if (buf->used + reclen > buf->len)
 		return -EINVAL;
 
 	de->namlen = namlen;

@@ -295,7 +297,7 @@ xfs_hack_filldir(
 	de->ino = ino;
 	de->d_type = d_type;
 	memcpy(de->name, name, namlen);
-	buf->used += sizeof(struct hack_dirent) + namlen;
+	buf->used += reclen;
 	return 0;
 }
 

@@ -335,7 +337,8 @@ xfs_file_readdir(
 		offset = filp->f_pos;
 
 	while (!eof) {
-		int reclen;
+		unsigned int reclen;
+
 		start_offset = offset;
 
 		buf.used = 0;

@@ -356,7 +359,8 @@ xfs_file_readdir(
 				goto done;
 			}
 
-			reclen = sizeof(struct hack_dirent) + de->namlen;
+			reclen = ALIGN(sizeof(struct hack_dirent) + de->namlen,
+				       sizeof(u64));
 			size -= reclen;
 			de = (struct hack_dirent *)((char *)de + reclen);
 			curr_offset = de->offset /* & 0x7fffffff */;

This patch should fix the issue seen on Alpha with unaligned accesses
in the new readdir code. By aligning each dirent to sizeof(u64) we'll
avoid unaligned accesses. To make doubly sure we're not hitting problems also rearrange struct hack_dirent to avoid holes.