Re: PAGE_SIZE Availability Inconsistency

[Anton Blanchard <anton@samba.org>]

Hi,

> Our current swap layout has issues with variable page size kernels.
> Instead of using the page size at runtime, base it on the minimum page
> size the architecture supports.

A hacked up patch to userspace utilities to test the kernel patch. BTW
It looks like there are some real bugs here:

            int pagesize = getpagesize();
            int rd;
            char buf[32768];

            rd = pagesize;
            if (rd < 8192)
                    rd = 8192;
            if (rd > sizeof(buf))
                    rd = sizeof(buf);
            if (lseek(fd, 0, SEEK_SET) != 0
                || read(fd, buf, rd) != rd)
                    goto io_error;
            if (may_be_swap(buf+pagesize) ||
                may_be_swap(buf+4096) || may_be_swap(buf+8192))
                    type = "swap";

If page size == 64kB wont we read past the end of buf?

Anton

Index: util-linux-2.12r/disk-utils/mkswap.c
===================================================================
--- util-linux-2.12r.orig/disk-utils/mkswap.c	2007-03-08 14:52:53.000000000 -0600
+++ util-linux-2.12r/disk-utils/mkswap.c	2007-03-08 14:58:09.000000000 -0600
@@ -169,7 +158,11 @@
 #ifdef PAGE_SIZE
 	defined_pagesize = PAGE_SIZE;
 #endif
+#ifdef __powerpc__
+	kernel_pagesize = 4096;
+#else
 	kernel_pagesize = getpagesize();
+#endif
 	pagesize = kernel_pagesize;
 
 	if (user_pagesize) {
Index: util-linux-2.12r/mount/get_label_uuid.c
===================================================================
--- util-linux-2.12r.orig/mount/get_label_uuid.c	2007-03-08 14:52:53.000000000 -0600
+++ util-linux-2.12r/mount/get_label_uuid.c	2007-03-08 14:58:09.000000000 -0600
@@ -79,7 +79,11 @@
 
 static int
 is_v1_swap_partition(int fd, char **label, char *uuid) {
+#ifdef __powerpc__
+	int n = 4096;
+#else
 	int n = getpagesize();
+#endif
 	char *buf = xmalloc(n);
 	struct swap_header_v1_2 *p = (struct swap_header_v1_2 *) buf;
 
Index: util-linux-2.12r/mount/mount_guess_fstype.c
===================================================================
--- util-linux-2.12r.orig/mount/mount_guess_fstype.c	2007-03-08 14:52:53.000000000 -0600
+++ util-linux-2.12r/mount/mount_guess_fstype.c	2007-03-08 14:54:25.000000000 -0600
@@ -462,7 +462,11 @@
     if (!type) {
 	    /* perhaps the user tries to mount the swap space
 	       on a new disk; warn her before she does mke2fs on it */
+#ifdef __powerpc__
+	    int pagesize = 4096;
+#else
 	    int pagesize = getpagesize();
+#endif
 	    int rd;
 	    char buf[32768];
 
Index: util-linux-2.12r/rescuept/rescuept.c
===================================================================
--- util-linux-2.12r.orig/rescuept/rescuept.c	2007-03-08 14:52:53.000000000 -0600
+++ util-linux-2.12r/rescuept/rescuept.c	2007-03-08 14:55:49.000000000 -0600
@@ -510,7 +510,11 @@
 		size = s.st_size / 512;
 	}
 
+#ifdef __powerpc__
+	pagesize = 4096;
+#else
 	pagesize = getpagesize();
+#endif
 	if (pagesize <= 0)
 		pagesize = 4096;
 	else if (pagesize > MAXPAGESZ) {