[linux-pm] Re: [PATCH] Don't explode on swsusp failure to find swap

[pavel at ucw.cz (Pavel Machek)]

Hi!

> > > > If we specify a swap device for swsusp using resume= kernel argument and
> > > > that device doesn't exist in the swap list, we end up calling
> > > > swsusp_free() before we have allocated pagedir_save. That causes us to
> > > > explode when trying to free it.
> > > > 
> > > > Pavel, does that look right ?
> > > 
> > > It looks like a workaround. We should not call swsusp_free in case
> > > device does not exists. Quick look did not reveal where the bug comes
> > > from, can you try to trace it?
> > > 								Pavel
> > 
> > Well, the bug comes from arch code calling swsusp_save() which fails,
> > then we call swsusp_free()
> 
> More specifically, arch suspend calls swsusp_save().
> 
> It fails and returns the error to the arch asm code, which itself
> returns it to it's caller swsusp_suspend(), which does that:
> 
>  	if ((error = swsusp_arch_suspend()))
> 		swsusp_free();

Ugh, swsusp_free should be totally unneccessary at this point; only
error returns are from the time before anything is allocated.

Does something like this help?

diff --git a/kernel/power/swsusp.c b/kernel/power/swsusp.c
--- a/kernel/power/swsusp.c
+++ b/kernel/power/swsusp.c
@@ -975,13 +975,6 @@ extern asmlinkage int swsusp_arch_resume
 
 asmlinkage int swsusp_save(void)
 {
-	int error = 0;
-
-	if ((error = swsusp_swap_check())) {
-		printk(KERN_ERR "swsusp: FATAL: cannot find swap device, try "
-				"swapon -a!\n");
-		return error;
-	}
 	return suspend_prepare_image();
 }
 
@@ -999,12 +992,19 @@ int swsusp_suspend(void)
 	 */
 	if ((error = device_power_down(PMSG_FREEZE))) {
 		local_irq_enable();
-		swsusp_free();
 		return error;
 	}
+
+	if ((error = swsusp_swap_check())) {
+		printk(KERN_ERR "swsusp: FATAL: cannot find swap device, try "
+				"swapon -a!\n");
+		local_irq_enable();
+		return error;
+	}
+
 	save_processor_state();
 	if ((error = swsusp_arch_suspend()))
-		swsusp_free();
+		printk("Error %d suspending\n", error);
 	/* Restore control flow magically appears here */
 	restore_processor_state();
 	BUG_ON (nr_copy_pages_check != nr_copy_pages);