klibc - Feb 2006 - Add swap support to fstype, second version

This patch adds support for swap detection to fstype (to be applied on 
top of the previous luks patch).

The patch is now against klibc's git tree instead of klibc-1.2.

Signed-off-by: David H?rdeman <david@2gen.com>

-- 

 fstype.c  |   42 ++++++++++++++++++++++++++++++------------
 swap_fs.h |   18 ++++++++++++++++++
 2 files changed, 48 insertions(+), 12 deletions(-)

-------------- next part --------------
Index: klibc/usr/kinit/fstype/fstype.c
==================================================================---
klibc.orig/usr/kinit/fstype/fstype.c	2006-02-05 11:09:31.000000000 +0100
+++ klibc/usr/kinit/fstype/fstype.c	2006-02-05 11:11:15.000000000 +0100
@@ -7,7 +7,7 @@
  *  FSSIZE - filesystem size (if known)
  *
  * We currently detect (in order):
- *  gzip, cramfs, romfs, xfs, luks, minix, ext3, ext2, reiserfs, jfs
+ *  gzip, cramfs, romfs, xfs, luks, minix, ext3, ext2, reiserfs, jfs, swap
  *
  * MINIX, ext3 and Reiserfs bits are currently untested.
  */
@@ -20,6 +20,7 @@
 #include <endian.h>
 #include <netinet/in.h>
 #include <sys/vfs.h>
+#include <asm/page.h>
 
 #define cpu_to_be32(x) __cpu_to_be32(x)	/* Needed by romfs_fs.h */
 
@@ -49,6 +50,9 @@
 
 #define BLOCK_SIZE 1024
 
+/* Swap needs the definition of block size */
+#include "swap_fs.h"
+
 static int gzip_image(const unsigned char *buf, unsigned long long *bytes)
 {
 	if (buf[0] == 037 && (buf[1] == 0213 || buf[1] == 0236)) {
@@ -182,6 +186,19 @@
 	return 0;
 }
 
+static int swap_image(const unsigned char *buf, unsigned long long *blocks)
+{
+	const struct swap_super_block *ssb +		(const struct swap_super_block *)buf;
+
+	if (!memcmp(ssb->magic, SWAP_MAGIC_1, SWAP_MAGIC_L) ||
+	    !memcmp(ssb->magic, SWAP_MAGIC_2, SWAP_MAGIC_L)) {
+		*blocks = 0;
+		return 1;
+	}
+	return 0;
+}
+
 struct imagetype {
 	off_t		block;
 	const char	name[12];
@@ -189,17 +206,18 @@
 };
 
 static struct imagetype images[] = {
-	{ 0,	"gzip",		gzip_image	},
-	{ 0,	"cramfs",	cramfs_image	},
-	{ 0,	"romfs",	romfs_image	},
-	{ 0,	"xfs",		xfs_image	},
-	{ 0,	"luks",		luks_image	},
-	{ 1,	"minix",	minix_image	},
-	{ 1,	"ext3",		ext3_image	},
-	{ 1,	"ext2",		ext2_image	},
-	{ 8,	"reiserfs",	reiserfs_image	},
-	{ 64,	"reiserfs",	reiserfs_image	},
-	{ 32,	"jfs",		jfs_image	}
+	{ 0,		"gzip",		gzip_image	},
+	{ 0,		"cramfs",	cramfs_image	},
+	{ 0,		"romfs",	romfs_image	},
+	{ 0,		"xfs",		xfs_image	},
+	{ 0,		"luks",		luks_image	},
+	{ 1,		"minix",	minix_image	},
+	{ 1,		"ext3",		ext3_image	},
+	{ 1,		"ext2",		ext2_image	},
+	{ 8,		"reiserfs",	reiserfs_image	},
+	{ 64,		"reiserfs",	reiserfs_image	},
+	{ 32,		"jfs",		jfs_image	},
+	{ SWAP_OFFSET,	"swap",		swap_image	}
 };
 
 int identify_fs(int fd, const char **fstype,
Index: klibc/usr/kinit/fstype/swap_fs.h
==================================================================--- /dev/null
1970-01-01 00:00:00.000000000 +0000
+++ klibc/usr/kinit/fstype/swap_fs.h	2006-02-05 11:10:01.000000000 +0100
@@ -0,0 +1,18 @@
+#ifndef __LINUX_SWAP_FS_H
+#define __LINUX_SWAP_FS_H
+
+/* The basic structures of the swap super block */
+#define SWAP_RESERVED_L		BLOCK_SIZE - 10
+#define SWAP_MAGIC_L		10
+#define SWAP_MAGIC_1		"SWAP-SPACE"
+#define SWAP_MAGIC_2		"SWAPSPACE2"
+/* The super block is the last block in the first page */
+#define SWAP_OFFSET		((PAGE_SIZE - BLOCK_SIZE) / BLOCK_SIZE)
+
+/* On-disk "super block" */
+struct swap_super_block {
+	char reserved[SWAP_RESERVED_L];
+	char magic[SWAP_MAGIC_L];
+};
+
+#endif

David H?rdeman wrote:
> +
> +/* The basic structures of the swap super block */
> +#define SWAP_RESERVED_L		BLOCK_SIZE - 10
> +#define SWAP_MAGIC_L		10
> +#define SWAP_MAGIC_1		"SWAP-SPACE"
> +#define SWAP_MAGIC_2		"SWAPSPACE2"
> +/* The super block is the last block in the first page */
> +#define SWAP_OFFSET		((PAGE_SIZE - BLOCK_SIZE) / BLOCK_SIZE)
> +
This is a bit confusing... on some architectures, PAGE_SIZE is 
undefined, because it's variable.  To get the page size, one has to do 
getpagesize(), but it's not even clear to me that that is the right thing.

I've applied the patch, but could you perhaps try to find out how this 
is supposed to work on architectures where page size is variable?

	-hpa