[linux-pm] Re: [RFC][PATCH] swsusp: warn about USB devices in documentation

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On Sun, 19 Feb 2006, Rafael J. Wysocki wrote:

> Hi,
> 
> The appended patch contains a warning about the possiblity to lose data
> if any filesystems on USB devices are mounted before suspend.
> 
> The A:-Q: part is from my correspondence with Alan Stern (thanks Alan).

> --- linux-2.6.16-rc3-mm1.orig/Documentation/power/swsusp.txt
> +++ linux-2.6.16-rc3-mm1/Documentation/power/swsusp.txt
> @@ -17,6 +17,11 @@ Some warnings, first.
>   * but it will probably only crash.
>   *
>   * (*) suspend/resume support is needed to make it safe.
> + *
> + * If you have any filesystems on USB devices mounted before suspend,
> + * they won't be mounted after resume and you may lose data, as though
> + * you have unplugged the USB devices with mounted filesystems on them
> + * (see the FAQ below for details).

This isn't quite right.  The filesystems _will_ still be mounted, but 
inaccessible (as though you have unplugged the USB devices with mounted 
filesystems on them).

Furthermore, this may or may not happen depending on your hardware and the
type of suspend.  So the "you _may_ lose data" part is good... but the
"they _won't_ be mounted" part is bad.  On some types of machines (I've
heard that Apple laptops work well) the process is very reliable; so long 
as the battery doesn't discharge entirely -- and provided you don't 
actually unplug the device while the machine is asleep -- you can resume 
safely with filesystems intact.

Can you update the patch to fix this paragraph?

Alan Stern


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