Re: fix reversed logic in device_area_is_valid

[Mike Snitzer <snitzer@redhat.com>]

On Mon, Jul 27 2009 at  9:21am -0400,
Mikulas Patocka <mpatocka@redhat.com> wrote:

> Hi
> 
> This patch fixes a bug introduced in 2.6.31-rc1. Targets that define 
> iterate_devices and don't contain any devices (such as dm-loop in fsio) 
> don't work.
> 
> Mikulas
> 
> ---
> 
> Fix reverse logic in device_area_is_valid
> 
> ->iterate_devices method calls the callback for every underlying device
> in the target. If the callback returns non-zero, iterate_devices exits
> and returns this value. If the callback returns zero for all the devices,
> iterate_devices returns zero.
> 
> The logic to check for invalid device areas was reversed.
> device_area_is_valid returned 0 on error and 1 on success.
> 
> Thus:
> - error was returned only if all the devices vere errorneous. If some of them
>   returned 1 (success), dm_calculate_queue_limits understood this as success.
> - if the target had no device (the example is dm-loop target in FSIO mode),
>   iterate_devices returned error straight away and dm_calculate_queue_limits
>   understood this as an error.
> 
> This patch reverses the logic so that 0 means success and 1 means error.
> 
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Nice catch, interesting that this was somehow missed.  All targets do
treat a non-zero return from .iterate_devices as an error.

We should probably rename device_area_is_valid to device_area_invalid.

Mike