On Sat, Aug 10, 2013 at 01:17:32PM -0600, 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>
>Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
>Reviewed-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Reviewed-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
>---
>v2: Updated the error message.
>
>---
> mm/memory_hotplug.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
>diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>index ca1dd3a..3bb1f39 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("Section-unaligned hotplug range: start 0x%llx, size 0x%llx\n",
>+ start, size);
>+ return -EINVAL;
>+ }
>+
>+ return 0;
>+}
>+
> /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
> int __ref add_memory(int nid, u64 start, u64 size)
> {
>@@ -1078,6 +1094,10 @@ int __ref add_memory(int nid, u64 start, u64 size)
> struct resource *res;
> int ret;
>
>+ ret = check_hotplug_memory_range(start, size);
>+ if (ret)
>+ return ret;
>+
> lock_memory_hotplug();
>
> res = register_memory_resource(start, size);
>@@ -1786,6 +1806,8 @@ void __ref remove_memory(int nid, u64 start, u64 size)
> {
> int ret;
>
>+ BUG_ON(check_hotplug_memory_range(start, size));
>+
> lock_memory_hotplug();
>
> /*
>
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