[patch] some fixes for is_mounted detection

[Kay Sievers]

On Mon, Jul 05, 2004 at 10:08:32PM +0200, David Zeuthen wrote:
> On Mon, 2004-07-05 at 22:07 +0200, Kay Sievers wrote:
> > > I think we should read the label, but probe_vfat() doesn't work on the
> > > floppy. Sure you don't have a floppy to test with? I can email you the
> > > image of the floppy if you want! :-)
> > 
> > No, no floppy or floppy drive left in my house :)
> > Is probe_msdos() also not working, maybe it isn't vfat on your disk.
> > 
> 
> When mounting it, mtab says vfat, so it must be a bug in probe_vfat()
> since mount(1) can figure it out. I can send the 1.44MB image if you
> want to look at it in a hexeditor or something.

  mount doesn't know anything about _this_ disk, it just tries to mount it
  and the kernel uses heuristics like blocksize jump-addresses to guess
  that it's fat. So I will add some of the heuristics too.

David, here is a try, to read your bad bad floppy :)

Kay
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Index: hald/linux/volume_id/volume_id.c
===================================================================
RCS file: /cvs/hal/hal/hald/linux/volume_id/volume_id.c,v
retrieving revision 1.9
diff -u -r1.9 volume_id.c
--- hald/linux/volume_id/volume_id.c	5 Jul 2004 19:57:22 -0000	1.9
+++ hald/linux/volume_id/volume_id.c	5 Jul 2004 22:40:52 -0000
@@ -211,7 +211,8 @@
 		if ((off < id->seekbuf_off) ||
 		    ((off + len) > (id->seekbuf_off + id->seekbuf_len))) {
 			dbg("read seekbuf off:0x%lx len:0x%x", off, len);
-			lseek64(id->fd, off, SEEK_SET);
+			if (lseek64(id->fd, off, SEEK_SET) == -1)
+				return NULL;
 			buf_len = read(id->fd, id->seekbuf, len);
 			dbg("got 0x%x (%i) bytes", buf_len, buf_len);
 			id->seekbuf_off = off;
@@ -462,9 +463,9 @@
 static int probe_msdos(struct volume_id *id)
 {
 	struct msdos_super_block {
-		__u8	ignored[3];
+		__u8	boot_jump[3];
 		__u8	sysid[8];
-		__u8	sector_size[2];
+		__u16	sector_size;
 		__u8	cluster_size;
 		__u16	reserved;
 		__u8	fats;
@@ -484,6 +485,8 @@
 		__u8	pmagic[2];
 	} __attribute__((__packed__)) *ms;
 
+	unsigned int	sector_size;
+
 	ms = (struct msdos_super_block *) get_buffer(id, 0, 0x200);
 	if (ms == NULL)
 		return -1;
@@ -494,7 +497,32 @@
 		goto found;
 	if (strncmp(ms->magic, "FAT12   ", 8) == 0)
 		goto found;
-	return -1;
+	/*
+	 * Bad, not finished. There are old floppies out there without a magic,
+ 	 * so we check for well known values and guess if it's a msdos volume
+	 */
+
+	/* boot jump address check */
+	if ((ms->boot_jump[0] != 0xeb || ms->boot_jump[2] != 0x90) &&
+	     ms->boot_jump[0] != 0xe9)
+		return -1;
+	/* heads check */
+	if (ms->heads == 0)
+		return -1;
+	/* sector size check */
+	sector_size = le16_to_cpu(ms->sector_size);
+	if (sector_size != 0x200 && sector_size != 0x400 &&
+	    sector_size != 0x800 && sector_size != 0x1000)
+		return -1;
+	/* cluster size check*/	
+	if (ms->cluster_size == 0 || (ms->cluster_size & (ms->cluster_size-1)))
+		return -1;
+	/* media check */
+	if (ms->media < 0xf8 && ms->media != 0xf0)
+		return -1;
+	/* fat count*/
+	if (ms->fats != 2)
+		return -1;
 
 found:
 	set_label_raw(id, ms->label, 11);
@@ -877,9 +905,11 @@
 	leaf_node_head = be32_to_cpu(bnode->leaf_head);
 	leaf_node_size = be16_to_cpu(bnode->node_size);
 
-	dbg("catalog leaf node 0x%x, size 0x%x", leaf_node_head, leaf_node_size);
+	dbg("catalog leaf node 0x%x, size 0x%x",
+	    leaf_node_head, leaf_node_size);
 
-	buf = get_buffer(id, cat_off + leaf_node_size, leaf_node_size);
+	buf = get_buffer(id, cat_off + (leaf_node_head * leaf_node_size),
+			 leaf_node_size);
 	if (buf == NULL)
 		goto found;
 
@@ -1132,14 +1162,17 @@
 		break;
 	case ALL:
 	default:
-		/* fill buffer with maximum */
-		/*get_buffer(id, 0, SB_BUFFER_SIZE);*/
+		/* read only minimal buffer, cause of the slow floppies */
 		rc = probe_vfat(id);
 		if (rc == 0)
 			break;
 		rc = probe_msdos(id);
 		if (rc == 0)
 			break;
+
+		/* fill buffer with maximum */
+		get_buffer(id, 0, SB_BUFFER_SIZE);
+
 		rc = probe_swap(id);
 		if (rc == 0)
 			break;
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