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SubjectRe: [PATCH] resource: make sure requested range intersects root range
On Thu, Jul 12, 2012 at 10:02:06AM +0800, Ram Pai wrote:
> On Wed, Jul 11, 2012 at 06:26:49PM +0300, Purdila, Octavian wrote:
> > On Wed, Jul 11, 2012 at 5:54 PM, Ram Pai <linuxram@us.ibm.com> wrote:
> > > On Wed, Jul 11, 2012 at 02:06:10PM +0300, Purdila, Octavian wrote:
> > >> On Wed, Jul 11, 2012 at 5:09 AM, Ram Pai <linuxram@us.ibm.com> wrote:
> > >>
> > >> >
> > >> > Wait.. I am not sure this will fix the problem entirely. The above check
> > >> > will handle the case where the range requested is entirey out of the
> > >> > root's range. But if the requested range overlapps that of the root
> > >> > range, we will still call __reserve_region_with_split() and end up with
> > >> > a recursion if there is a overflow. Wont we?
> > >> >
> > >>
> > >> Good catch. I will fix this as well as address Andrew's and Joe's
> > >> comments in a new patch. The only question is how to handle the
> > >> overlap case:
> > >>
> > >> (a) abort the whole request or
> > >>
> > >> (b) try to reserve the part that overlaps (and adjust the request to
> > >> avoid the overflow)
> > >>
> > >> I think (b) is more in line with the current implementation for reservations.
> > >
> > >
> > > I prefer (b). following patch should handle that.
> > >
> > > diff --git a/kernel/resource.c b/kernel/resource.c
> > > index e1d2b8e..dd87fde 100644
> > > --- a/kernel/resource.c
> > > +++ b/kernel/resource.c
> > > @@ -780,6 +780,10 @@ static void __init __reserve_region_with_split(struct resource *root,
> > >
> > > if (conflict->start > start)
> > > __reserve_region_with_split(root, start, conflict->start-1, name);
> > > +
> > > + if (conflict->end == parent->end )
> > > + return;
> > > +
> > > if (conflict->end < end)
> > > __reserve_region_with_split(root, conflict->end+1, end, name);
> > > }
> > >
> >
> > I don't think this covers all cases, e.g. if root range starts
> > somewhere above 0 and the request is below the root start point.
>

Ok. I see your point. Here is a proposal that incoporates the best of all
the proposals till now..


diff --git a/kernel/resource.c b/kernel/resource.c
index e1d2b8e..c6f4958 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -789,7 +789,19 @@ void __init reserve_region_with_split(struct resource *root,
const char *name)
{
write_lock(&resource_lock);
- __reserve_region_with_split(root, start, end, name);
+ if (start > root->end || end < root->start) {
+ pr_err("Requested range (0x%llx-0x%llx) not in root range (0x%llx-0x%llx)\n",
+ (unsigned long long)start, (unsigned long long)end,
+ (unsigned long long)root->start,
+ (unsigned long long)root->end);
+ dump_stack();
+ } else {
+ if (start < root->start)
+ start = root->start;
+ if (end > root->end)
+ end = root->end;
+ __reserve_region_with_split(root, start, end, name);
+ }
write_unlock(&resource_lock);
}

Offcourse; it does not warn when the request is partially out of root's range.
But that should be ok, because its still a valid request.
RP



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