[PATCH] swsusp: fix devfs breakage introduced in 2.6.6

From: Pavel Machek <pavel@ucw.cz>

This fixes bad interaction between devfs and swsusp.

Check whether the swap device is the specified resume device, irrespective of
whether they are specified by identical names.

(Thus, device inode aliasing is allowed.  You can say /dev/hda4 instead of
/dev/ide/host0/bus0/target0/lun0/part4 [if using devfs] and they'll be
considered the same device.  This is *necessary* for devfs, since the resume
code can only recognize the form /dev/hda4, but the suspend code would like
the long name [as shown in 'cat /proc/mounts'].)

[Thanks to devfs hero whose name I forgot.]

kernel/power/swsusp.c

@@ -222,10 +222,30 @@ static void mark_swapfiles(swp_entry_t prev, int mode)
 	__free_page(page);
 }
 
+
+/*
+ * Check whether the swap device is the specified resume
+ * device, irrespective of whether they are specified by
+ * identical names.
+ *
+ * (Thus, device inode aliasing is allowed.  You can say /dev/hda4
+ * instead of /dev/ide/host0/bus0/target0/lun0/part4 [if using devfs]
+ * and they'll be considered the same device.  This is *necessary* for
+ * devfs, since the resume code can only recognize the form /dev/hda4,
+ * but the suspend code would see the long name.)
+ */
+static int is_resume_device(const struct swap_info_struct *swap_info)
+{
+	struct file *file = swap_info->swap_file;
+	struct inode *inode = file->f_dentry->d_inode;
+
+	return S_ISBLK(inode->i_mode) &&
+		resume_device == MKDEV(imajor(inode), iminor(inode));
+}
+
 static void read_swapfiles(void) /* This is called before saving image */
 {
 	int i, len;
-	static char buff[sizeof(resume_file)], *sname;
 	
 	len=strlen(resume_file);
 	root_swap = 0xFFFF;
@@ -244,17 +264,10 @@ static void read_swapfiles(void) /* This is called before saving image */
 					swapfile_used[i] = SWAPFILE_IGNORED;				  
 			} else {
 	  			/* we ignore all swap devices that are not the resume_file */
-				sname = d_path(swap_info[i].swap_file->f_dentry,
-					       swap_info[i].swap_file->f_vfsmnt,
-					       buff,
-					       sizeof(buff));
-				if (!strcmp(sname, resume_file)) {
+				if (is_resume_device(&swap_info[i])) {
 					swapfile_used[i] = SWAPFILE_SUSPEND;
 					root_swap = i;
 				} else {
-#if 0
-					printk( "Resume: device %s (%x != %x) ignored\n", swap_info[i].swap_file->d_name.name, swap_info[i].swap_device, resume_device );				  
-#endif
 				  	swapfile_used[i] = SWAPFILE_IGNORED;
 				}
 			}