Re: [PATCH v3 5/6] mm: Fix memory_failure() handling of dax-namespace metadata
On 13.01.21 08:35, Dan Williams wrote:
> Given 'struct dev_pagemap' spans both data pages and metadata pages be
> careful to consult the altmap if present to delineate metadata. In fact
> the pfn_first() helper already identifies the first valid data pfn, so
> export that helper for other code paths via pgmap_pfn_valid().
>
> Other usage of get_dev_pagemap() are not a concern because those are
> operating on known data pfns having been looking up by get_user_pages().
> I.e. metadata pfns are never user mapped.
>
> Cc: Naoya Horiguchi
> Cc: Andrew Morton
> Reported-by: David Hildenbrand
> Signed-off-by: Dan Williams
> ---
> include/linux/memremap.h |6 ++
> mm/memory-failure.c |6 ++
> mm/memremap.c| 15 +++
> 3 files changed, 27 insertions(+)
>
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 79c49e7f5c30..f5b464daeeca 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -137,6 +137,7 @@ void *devm_memremap_pages(struct device *dev, struct
> dev_pagemap *pgmap);
> void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
> struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
> struct dev_pagemap *pgmap);
> +bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
>
> unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
> void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
> @@ -165,6 +166,11 @@ static inline struct dev_pagemap
> *get_dev_pagemap(unsigned long pfn,
> return NULL;
> }
>
> +static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long
> pfn)
> +{
> + return false;
> +}
> +
> static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
> {
> return 0;
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 78b173c7190c..541569cb4a99 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1308,6 +1308,12 @@ static int memory_failure_dev_pagemap(unsigned long
> pfn, int flags,
>*/
> put_page(page);
>
> + /* device metadata space is not recoverable */
> + if (!pgmap_pfn_valid(pgmap, pfn)) {
> + rc = -ENXIO;
> + goto out;
> + }
> +
> /*
>* Prevent the inode from being freed while we are interrogating
>* the address_space, typically this would be handled by
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 16b2fb482da1..2455bac89506 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -80,6 +80,21 @@ static unsigned long pfn_first(struct dev_pagemap *pgmap,
> int range_id)
> return pfn + vmem_altmap_offset(pgmap_altmap(pgmap));
> }
>
> +bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
> +{
> + int i;
> +
> + for (i = 0; i < pgmap->nr_range; i++) {
> + struct range *range = &pgmap->ranges[i];
> +
> + if (pfn >= PHYS_PFN(range->start) &&
> + pfn <= PHYS_PFN(range->end))
> + return pfn >= pfn_first(pgmap, i);
> + }
> +
> + return false;
> +}
> +
> static unsigned long pfn_end(struct dev_pagemap *pgmap, int range_id)
> {
> const struct range *range = &pgmap->ranges[range_id];
>
LGTM
Reviewed-by: David Hildenbrand
--
Thanks,
David / dhildenb
[PATCH v3 5/6] mm: Fix memory_failure() handling of dax-namespace metadata
Given 'struct dev_pagemap' spans both data pages and metadata pages be
careful to consult the altmap if present to delineate metadata. In fact
the pfn_first() helper already identifies the first valid data pfn, so
export that helper for other code paths via pgmap_pfn_valid().
Other usage of get_dev_pagemap() are not a concern because those are
operating on known data pfns having been looking up by get_user_pages().
I.e. metadata pfns are never user mapped.
Cc: Naoya Horiguchi
Cc: Andrew Morton
Reported-by: David Hildenbrand
Signed-off-by: Dan Williams
---
include/linux/memremap.h |6 ++
mm/memory-failure.c |6 ++
mm/memremap.c| 15 +++
3 files changed, 27 insertions(+)
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 79c49e7f5c30..f5b464daeeca 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -137,6 +137,7 @@ void *devm_memremap_pages(struct device *dev, struct
dev_pagemap *pgmap);
void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
struct dev_pagemap *pgmap);
+bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
@@ -165,6 +166,11 @@ static inline struct dev_pagemap *get_dev_pagemap(unsigned
long pfn,
return NULL;
}
+static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long
pfn)
+{
+ return false;
+}
+
static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
{
return 0;
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 78b173c7190c..541569cb4a99 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1308,6 +1308,12 @@ static int memory_failure_dev_pagemap(unsigned long pfn,
int flags,
*/
put_page(page);
+ /* device metadata space is not recoverable */
+ if (!pgmap_pfn_valid(pgmap, pfn)) {
+ rc = -ENXIO;
+ goto out;
+ }
+
/*
* Prevent the inode from being freed while we are interrogating
* the address_space, typically this would be handled by
diff --git a/mm/memremap.c b/mm/memremap.c
index 16b2fb482da1..2455bac89506 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -80,6 +80,21 @@ static unsigned long pfn_first(struct dev_pagemap *pgmap,
int range_id)
return pfn + vmem_altmap_offset(pgmap_altmap(pgmap));
}
+bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
+{
+ int i;
+
+ for (i = 0; i < pgmap->nr_range; i++) {
+ struct range *range = &pgmap->ranges[i];
+
+ if (pfn >= PHYS_PFN(range->start) &&
+ pfn <= PHYS_PFN(range->end))
+ return pfn >= pfn_first(pgmap, i);
+ }
+
+ return false;
+}
+
static unsigned long pfn_end(struct dev_pagemap *pgmap, int range_id)
{
const struct range *range = &pgmap->ranges[range_id];
