On Thu, Apr 11, 2013 at 10:30:02AM -0600, Toshi Kani wrote:
> On Wed, 2013-04-10 at 15:24 -0700, Andrew Morton wrote:
> > On Wed, 10 Apr 2013 15:08:29 -0700 (PDT) David Rientjes <rientjes@xxxxxxxxxx> wrote:
> >
> > > On Wed, 10 Apr 2013, Toshi Kani wrote:
> > >
> > > > > I'll switch it to GFP_ATOMIC. Which is horridly lame but the
> > > > > allocation is small and alternatives are unobvious.
> > > >
> > > > Great! Again, thanks for the update!
> > >
> > > release_mem_region_adjustable() allocates at most one struct resource, so
> > > why not do kmalloc(sizeof(struct resource), GFP_KERNEL) before taking
> > > resource_lock and then testing whether it's NULL or not when splitting?
> > > It unnecessarily allocates memory when there's no split, but
> > > __remove_pages() shouldn't be a hotpath.
> >
> > yup.
> >
> > --- a/kernel/resource.c~resource-add-release_mem_region_adjustable-fix-fix
> > +++ a/kernel/resource.c
> > @@ -1046,7 +1046,8 @@ int release_mem_region_adjustable(struct
> > resource_size_t start, resource_size_t size)
> > {
> > struct resource **p;
> > - struct resource *res, *new;
> > + struct resource *res;
> > + struct resource *new_res;
> > resource_size_t end;
> > int ret = -EINVAL;
> >
> > @@ -1054,6 +1055,9 @@ int release_mem_region_adjustable(struct
> > if ((start < parent->start) || (end > parent->end))
> > return ret;
> >
> > + /* The kzalloc() result gets checked later */
> > + new_res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> > +
> > p = &parent->child;
> > write_lock(&resource_lock);
> >
> > @@ -1091,32 +1095,33 @@ int release_mem_region_adjustable(struct
> > start - res->start);
> > } else {
> > /* split into two entries */
> > - new = kzalloc(sizeof(struct resource), GFP_ATOMIC);
> > - if (!new) {
> > + if (!new_res) {
> > ret = -ENOMEM;
> > break;
> > }
> > - new->name = res->name;
> > - new->start = end + 1;
> > - new->end = res->end;
> > - new->flags = res->flags;
> > - new->parent = res->parent;
> > - new->sibling = res->sibling;
> > - new->child = NULL;
> > + new_res->name = res->name;
> > + new_res->start = end + 1;
> > + new_res->end = res->end;
> > + new_res->flags = res->flags;
> > + new_res->parent = res->parent;
> > + new_res->sibling = res->sibling;
> > + new_res->child = NULL;
> >
> > ret = __adjust_resource(res, res->start,
> > start - res->start);
> > if (ret) {
> > - kfree(new);
> > + kfree(new_res);
> > break;
> > }
>
> The kfree() in the if-statement above is not necessary since kfree() is
> called before the return at the end. That is, the if-statement needs to
> be:
> if (ret)
> break;
>
> With this change, I confirmed that all my test cases passed (with all
> the config debug options this time :). With the change:
>
> Reviewed-by: Toshi Kani <toshi.kani@xxxxxx>
I am not confortable witht the assumption, that when a split takes
place, the children are assumed to be in the lower entry. Probably a
warning to that effect, would help quickly
nail down the problem, if such a case does encounter ?
Otherwise this looks fine. Sorry for the delayed reply. Was out.
Reviewed-by: Ram Pai <linuxram@xxxxxxxxxx>
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