Check-in swap_super.c

and update a test that uses it.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>

1 files changed, 83 insertions, 0 deletions

diff --git a/swap_super.c b/swap_super.c
new file mode 100644
index 0000000..afcedf3
--- /dev/null
+++ b/swap_super.c
@@ -0,0 +1,83 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mount.h>
+/*
+ * This is a tiny test program to endian-swap
+ * the superblock on a given device.
+ * We simply read 4k from where the superblock should be
+ * do the swap, and write it back
+ * Don't use this on a real array, use mdadm.
+ */
+
+#define MD_RESERVED_BYTES		(64 * 1024)
+#define MD_RESERVED_SECTORS		(MD_RESERVED_BYTES / 512)
+
+#define MD_NEW_SIZE_SECTORS(x)		((x & ~(MD_RESERVED_SECTORS - 1)) - MD_RESERVED_SECTORS)
+
+main(int argc, char *argv[])
+{
+	int fd, i;
+	unsigned long size;
+	unsigned long long offset;
+	char super[4096];
+	if (argc != 2) {
+		fprintf(stderr, "Usage: swap_super device\n");
+		exit(1);
+	}
+	fd = open(argv[1], O_RDWR);
+	if (fd<0) {
+		perror(argv[1]);
+		exit(1);
+	}
+	if (ioctl(fd, BLKGETSIZE, &size)) {
+		perror("BLKGETSIZE");
+		exit(1);
+	}
+	offset = MD_NEW_SIZE_SECTORS(size) * 512LL;
+	if (lseek64(fd, offset, 0) < 0LL) {
+		perror("lseek64");
+		exit(1);
+	}
+	if (read(fd, super, 4096) != 4096) {
+		perror("read");
+		exit(1);
+	}
+
+
+	for (i=0; i < 4096 ; i+=4) {
+		char t = super[i];
+		super[i] = super[i+3];
+		super[i+3] = t;
+		t=super[i+1];
+		super[i+1]=super[i+2];
+		super[i+2]=t;
+	}
+	/* swap the u64 events counters */
+	for (i=0; i<4; i++) {
+		/* events_hi and events_lo */
+		char t=super[32*4+7*4 +i];
+		super[32*4+7*4 +i] = super[32*4+8*4 +i];
+		super[32*4+8*4 +i] = t;
+
+		/* cp_events_hi and cp_events_lo */
+		t=super[32*4+9*4 +i];
+		super[32*4+9*4 +i] = super[32*4+10*4 +i];
+		super[32*4+10*4 +i] = t;
+	}
+
+
+	if (lseek64(fd, offset, 0) < 0LL) {
+		perror("lseek64");
+		exit(1);
+	}
+	if (write(fd, super, 4096) != 4096) {
+		perror("write");
+		exit(1);
+	}
+	exit(0);
+
+}
+
+