diff mbox series

[v6,2/8] mm,memory_hotplug: Relax fully spanned sections check

Message ID 20210406111115.8953-3-osalvador@suse.de (mailing list archive)
State New, archived
Headers show
Series [v6,1/8] drivers/base/memory: Introduce memory_block_{online,offline} | expand

Commit Message

Oscar Salvador April 6, 2021, 11:11 a.m. UTC 
When using self-hosted vmemmap pages, the number of pages passed to
{online,offline}_pages might not fully span sections, but they always
fully span pageblocks.
Relax the check account for that case.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/memory_hotplug.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Comments

David Hildenbrand April 6, 2021, 3:32 p.m. UTC | #1 
On 06.04.21 13:11, Oscar Salvador wrote:
> When using self-hosted vmemmap pages, the number of pages passed to
> {online,offline}_pages might not fully span sections, but they always
> fully span pageblocks.
> Relax the check account for that case.
> 
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
>   mm/memory_hotplug.c | 16 ++++++++++++----
>   1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 0cdbbfbc5757..5fe3e3942b19 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -838,9 +838,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
>   	int ret;
>   	struct memory_notify arg;
>   
> -	/* We can only online full sections (e.g., SECTION_IS_ONLINE) */
> +	/* We can only offline full sections (e.g., SECTION_IS_ONLINE).
> +	 * However, when using e.g: memmap_on_memory, some pages are initialized
> +	 * prior to calling in here. The remaining amount of pages must be
> +	 * pageblock aligned.
> +	 */
>   	if (WARN_ON_ONCE(!nr_pages ||
> -			 !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
> +			 !IS_ALIGNED(pfn | nr_pages, pageblock_nr_pages)))
>   		return -EINVAL;
>   
>   	mem_hotplug_begin();
> @@ -1573,9 +1577,13 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>   	int ret, node;
>   	char *reason;
>   
> -	/* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
> +	/* We can only offline full sections (e.g., SECTION_IS_ONLINE).
> +	 * However, when using e.g: memmap_on_memory, some pages are initialized
> +	 * prior to calling in here. The remaining amount of pages must be
> +	 * pageblock aligned.
> +	 */
>   	if (WARN_ON_ONCE(!nr_pages ||
> -			 !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
> +			 !IS_ALIGNED(start_pfn | nr_pages, pageblock_nr_pages)))
>   		return -EINVAL;
>   
>   	mem_hotplug_begin();
> 

I'd only relax start_pfn. That way the function is pretty much 
impossible to abuse for sub-section onlining/offlining.

if (WARN_ON_ONCE(!nr_pages ||
		 !IS_ALIGNED(start_pfn, pageblock_nr_pages))
		 !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
Oscar Salvador April 6, 2021, 4:33 p.m. UTC | #2 
On 2021-04-06 17:32, David Hildenbrand wrote:
> I'd only relax start_pfn. That way the function is pretty much
> impossible to abuse for sub-section onlining/offlining.
> 
> if (WARN_ON_ONCE(!nr_pages ||
> 		 !IS_ALIGNED(start_pfn, pageblock_nr_pages))
> 		 !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))

But this is not going to work.
When using memmap_on_memory, the nr of pages that online_pages() and 
offline_pages() get might be less than PAGES_PER_SECTION, so this check 
will always blow us up.
David Hildenbrand April 6, 2021, 8:43 p.m. UTC | #3 
> Am 06.04.2021 um 18:34 schrieb Oscar Salvador <osalvador@suse.de>:
> 
> On 2021-04-06 17:32, David Hildenbrand wrote:
>> I'd only relax start_pfn. That way the function is pretty much
>> impossible to abuse for sub-section onlining/offlining.
>> if (WARN_ON_ONCE(!nr_pages ||
>>         !IS_ALIGNED(start_pfn, pageblock_nr_pages))
>>         !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
> 
> But this is not going to work.
> When using memmap_on_memory, the nr of pages that online_pages() and offline_pages() get might be less than PAGES_PER_SECTION, so this check will always blow us up.

But not end_pfn as given in my version or what am I missing?


> -- 
> Oscar Salvador
> SUSE L3
>
Oscar Salvador April 7, 2021, 7:42 a.m. UTC | #4 
On Tue, Apr 06, 2021 at 10:43:01PM +0200, David Hildenbrand wrote:
> But not end_pfn as given in my version or what am I missing?

Nah, was my fault, I managed to see:

 if (WARN_ON_ONCE(!nr_pages ||
         !IS_ALIGNED(start_pfn, pageblock_nr_pages))
         !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))

which would not work.

I agree that keeping the PAGES_PER_SECTION check maks this safer, so this all
should have been:

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0cdbbfbc5757..25e59d5dc13c 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -838,9 +838,14 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
        int ret;
        struct memory_notify arg;
 
-       /* We can only online full sections (e.g., SECTION_IS_ONLINE) */
+       /* We can only offline full sections (e.g., SECTION_IS_ONLINE).
+        * However, when using e.g: memmap_on_memory, some pages are initialized
+        * prior to calling in here. The remaining amount of pages must be
+        * pageblock aligned.
+        */
        if (WARN_ON_ONCE(!nr_pages ||
-                        !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
+                        !IS_ALIGNED(pfn, pageblock_nr_pages) ||
+                        !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION)))
                return -EINVAL;
 
        mem_hotplug_begin();
@@ -1573,9 +1578,14 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
        int ret, node;
        char *reason;
 
-       /* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
+       /* We can only offline full sections (e.g., SECTION_IS_ONLINE).
+        * However, when using e.g: memmap_on_memory, some pages are initialized
+        * prior to calling in here. The remaining amount of pages must be
+        * pageblock aligned.
+        */
        if (WARN_ON_ONCE(!nr_pages ||
-                        !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
+                        !IS_ALIGNED(start_pfn, pageblock_nr_pages) ||
+                        !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
                return -EINVAL;
 
        mem_hotplug_begin();
David Hildenbrand April 7, 2021, 7:43 a.m. UTC | #5 
On 07.04.21 09:42, Oscar Salvador wrote:
> On Tue, Apr 06, 2021 at 10:43:01PM +0200, David Hildenbrand wrote:
>> But not end_pfn as given in my version or what am I missing?
> 
> Nah, was my fault, I managed to see:
> 
>   if (WARN_ON_ONCE(!nr_pages ||
>           !IS_ALIGNED(start_pfn, pageblock_nr_pages))
>           !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
> 
> which would not work.
> 
> I agree that keeping the PAGES_PER_SECTION check maks this safer, so this all
> should have been:
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 0cdbbfbc5757..25e59d5dc13c 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -838,9 +838,14 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
>          int ret;
>          struct memory_notify arg;
>   
> -       /* We can only online full sections (e.g., SECTION_IS_ONLINE) */
> +       /* We can only offline full sections (e.g., SECTION_IS_ONLINE).
> +        * However, when using e.g: memmap_on_memory, some pages are initialized
> +        * prior to calling in here. The remaining amount of pages must be
> +        * pageblock aligned.
> +        */
>          if (WARN_ON_ONCE(!nr_pages ||
> -                        !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
> +                        !IS_ALIGNED(pfn, pageblock_nr_pages) ||
> +                        !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION)))
>                  return -EINVAL;
>   
>          mem_hotplug_begin();
> @@ -1573,9 +1578,14 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>          int ret, node;
>          char *reason;
>   
> -       /* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
> +       /* We can only offline full sections (e.g., SECTION_IS_ONLINE).
> +        * However, when using e.g: memmap_on_memory, some pages are initialized
> +        * prior to calling in here. The remaining amount of pages must be
> +        * pageblock aligned.
> +        */
>          if (WARN_ON_ONCE(!nr_pages ||
> -                        !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
> +                        !IS_ALIGNED(start_pfn, pageblock_nr_pages) ||
> +                        !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
>                  return -EINVAL;
>   
>          mem_hotplug_begin();
> 
>   
> 

Reviewed-by: David Hildenbrand <david@redhat.com>
diff mbox series

Patch

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0cdbbfbc5757..5fe3e3942b19 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -838,9 +838,13 @@  int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
 	int ret;
 	struct memory_notify arg;
 
-	/* We can only online full sections (e.g., SECTION_IS_ONLINE) */
+	/* We can only offline full sections (e.g., SECTION_IS_ONLINE).
+	 * However, when using e.g: memmap_on_memory, some pages are initialized
+	 * prior to calling in here. The remaining amount of pages must be
+	 * pageblock aligned.
+	 */
 	if (WARN_ON_ONCE(!nr_pages ||
-			 !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
+			 !IS_ALIGNED(pfn | nr_pages, pageblock_nr_pages)))
 		return -EINVAL;
 
 	mem_hotplug_begin();
@@ -1573,9 +1577,13 @@  int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 	int ret, node;
 	char *reason;
 
-	/* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
+	/* We can only offline full sections (e.g., SECTION_IS_ONLINE).
+	 * However, when using e.g: memmap_on_memory, some pages are initialized
+	 * prior to calling in here. The remaining amount of pages must be
+	 * pageblock aligned.
+	 */
 	if (WARN_ON_ONCE(!nr_pages ||
-			 !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
+			 !IS_ALIGNED(start_pfn | nr_pages, pageblock_nr_pages)))
 		return -EINVAL;
 
 	mem_hotplug_begin();