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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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