On Fri, 2013-08-09 at 13:52 +0800, Tang Chen wrote:
> On 08/09/2013 12:47 AM, Toshi Kani wrote:
> > add_memory() and remove_memory() can only handle a memory range aligned
> > with section. There are problems when an unaligned range is added and
> > then deleted as follows:
> >
> > - add_memory() with an unaligned range succeeds, but __add_pages()
> > called from add_memory() adds a whole section of pages even though
> > a given memory range is less than the section size.
> > - remove_memory() to the added unaligned range hits BUG_ON() in
> > __remove_pages().
> >
> > This patch changes add_memory() and remove_memory() to check if a given
> > memory range is aligned with section at the beginning. As the result,
> > add_memory() fails with -EINVAL when a given range is unaligned, and
> > does not add such memory range. This prevents remove_memory() to be
> > called with an unaligned range as well. Note that remove_memory() has
> > to use BUG_ON() since this function cannot fail.
> >
> > Signed-off-by: Toshi Kani<toshi.kani@xxxxxx>
> > ---
> > mm/memory_hotplug.c | 22 ++++++++++++++++++++++
> > 1 file changed, 22 insertions(+)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index ca1dd3a..ac182de 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1069,6 +1069,22 @@ out:
> > return ret;
> > }
> >
> > +static int check_hotplug_memory_range(u64 start, u64 size)
> > +{
> > + u64 start_pfn = start>> PAGE_SHIFT;
> > + u64 nr_pages = size>> PAGE_SHIFT;
> > +
> > + /* Memory range must be aligned with section */
> > + if ((start_pfn& ~PAGE_SECTION_MASK) ||
> > + (nr_pages % PAGES_PER_SECTION) || (!nr_pages)) {
> > + pr_err("Unsupported hotplug range: start 0x%llx, size 0x%llx\n",
> > + start, size);
>
> I think the message here should tell users that only support range aligned
> to section. Others seems OK to me.
OK, I will change the message to something like this:
pr_err("Section-unaligned hotplug range: start 0x%llx, size 0x%llx\n",
start, size);
> Reviewed-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Thanks!
-Toshi
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