linux-kernel - Re: [PATCH v2] resource: make sure requested range is included in the root range

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Message-ID: <CAE1zotK_R4QY9OoNCmfOx6+dm4R-DseB_nEsSmwaTGZNZM0nJg@mail.gmail.com>
Date:	Fri, 13 Jul 2012 11:38:16 +0300
From:	Octavian Purdila <octavian.purdila@...el.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Ram Pai <linuxram@...ibm.com>
Subject: Re: [PATCH v2] resource: make sure requested range is included in the
 root range

On Thu, Jul 12, 2012 at 10:02 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:

> Why don't you fix this right where the problem occurs, in
> __reserve_region_with_split(), with something like this:
>
>         if (end > conflict->start && conflict->start > start)
>                 __reserve_region_with_split(root, start,
> conflict->start-1, name);
>         if (start < conflict->end && conflict->end < end && )
>                 __reserve_region_with_split(root, conflict->end+1, end, name);
>

I am not sure this will behave properly in the overlapping cases.
Consider start=10, end=150, root->start=100, root->end=200.

In this case only the first condition above will be true (150 > 100 &&
100 > 10) and we will try to reserve  [10, 99] - which will return
nicely. But we will not reserve [100, 150].

But more important is the fact that by fixing the issue here we won't
be able to log the error and give a chance to upper layer fixing the
problem.

>> +               if (start > root->end || end < root->start) {
>> +                       abort = 1;
>> +                       pr_err("unable to fix request, aborting it\n");
>
> This message doesn't contain any useful information (range/root/etc).
>

Good point, I will remove it.
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