[PATCH 1/2 v2] fs/proc/task_mmu: report SOFT_DIRTY bits through the PAGEMAP_SCAN ioctl

[PATCH 1/2 v2] fs/proc/task_mmu: report SOFT_DIRTY bits through the PAGEMAP_SCAN ioctl

[Andrei Vagin]

The PAGEMAP_SCAN ioctl returns information regarding page table entries.
It is more efficient compared to reading pagemap files. CRIU can start
to utilize this ioctl, but it needs info about soft-dirty bits to track
memory changes.

We are aware of a new method for tracking memory changes implemented in
the PAGEMAP_SCAN ioctl. For CRIU, the primary advantage of this method
is its usability by unprivileged users. However, it is not feasible to
transparently replace the soft-dirty tracker with the new one. The main
problem here is userfault descriptors that have to be preserved between
pre-dump iterations.  It means criu continues supporting the soft-dirty
method to avoid breakage for current users. The new method will be
implemented as a separate feature.

Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Andrei Vagin <avagin@google.com>
---
v2: check the soft-dirty bit in pagemap_page_category

 Documentation/admin-guide/mm/pagemap.rst |  1 +
 fs/proc/task_mmu.c                       | 17 ++++++++++++++++-
 include/uapi/linux/fs.h                  |  1 +
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
index fe17cf210426..f5f065c67615 100644
--- a/Documentation/admin-guide/mm/pagemap.rst
+++ b/Documentation/admin-guide/mm/pagemap.rst
@@ -253,6 +253,7 @@ Following flags about pages are currently supported:
 - ``PAGE_IS_SWAPPED`` - Page is in swapped
 - ``PAGE_IS_PFNZERO`` - Page has zero PFN
 - ``PAGE_IS_HUGE`` - Page is THP or Hugetlb backed
+- ``PAGE_IS_SOFT_DIRTY`` - Page is soft-dirty
 
 The ``struct pm_scan_arg`` is used as the argument of the IOCTL.
 
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ef2eb12906da..51e0ec658457 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1761,7 +1761,7 @@ static int pagemap_release(struct inode *inode, struct file *file)
 #define PM_SCAN_CATEGORIES	(PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN |	\
 				 PAGE_IS_FILE |	PAGE_IS_PRESENT |	\
 				 PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |	\
-				 PAGE_IS_HUGE)
+				 PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY)
 #define PM_SCAN_FLAGS		(PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC)
 
 struct pagemap_scan_private {
@@ -1793,6 +1793,8 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
 
 		if (is_zero_pfn(pte_pfn(pte)))
 			categories |= PAGE_IS_PFNZERO;
+		if (pte_soft_dirty(pte))
+			categories |= PAGE_IS_SOFT_DIRTY;
 	} else if (is_swap_pte(pte)) {
 		swp_entry_t swp;
 
@@ -1806,6 +1808,8 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
 			    !PageAnon(pfn_swap_entry_to_page(swp)))
 				categories |= PAGE_IS_FILE;
 		}
+		if (pte_swp_soft_dirty(pte))
+			categories |= PAGE_IS_SOFT_DIRTY;
 	}
 
 	return categories;
@@ -1853,12 +1857,16 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p,
 
 		if (is_zero_pfn(pmd_pfn(pmd)))
 			categories |= PAGE_IS_PFNZERO;
+		if (pmd_soft_dirty(pmd))
+			categories |= PAGE_IS_SOFT_DIRTY;
 	} else if (is_swap_pmd(pmd)) {
 		swp_entry_t swp;
 
 		categories |= PAGE_IS_SWAPPED;
 		if (!pmd_swp_uffd_wp(pmd))
 			categories |= PAGE_IS_WRITTEN;
+		if (pmd_swp_soft_dirty(pmd))
+			categories |= PAGE_IS_SOFT_DIRTY;
 
 		if (p->masks_of_interest & PAGE_IS_FILE) {
 			swp = pmd_to_swp_entry(pmd);
@@ -1905,10 +1913,14 @@ static unsigned long pagemap_hugetlb_category(pte_t pte)
 			categories |= PAGE_IS_FILE;
 		if (is_zero_pfn(pte_pfn(pte)))
 			categories |= PAGE_IS_PFNZERO;
+		if (pte_soft_dirty(pte))
+			categories |= PAGE_IS_SOFT_DIRTY;
 	} else if (is_swap_pte(pte)) {
 		categories |= PAGE_IS_SWAPPED;
 		if (!pte_swp_uffd_wp_any(pte))
 			categories |= PAGE_IS_WRITTEN;
+		if (pte_swp_soft_dirty(pte))
+			categories |= PAGE_IS_SOFT_DIRTY;
 	}
 
 	return categories;
@@ -1991,6 +2003,9 @@ static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
 	if (vma->vm_flags & VM_PFNMAP)
 		return 1;
 
+	if (vma->vm_flags & VM_SOFTDIRTY)
+		vma_category |= PAGE_IS_SOFT_DIRTY;
+
 	if (!pagemap_scan_is_interesting_vma(vma_category, p))
 		return 1;
 
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index da43810b7485..48ad69f7722e 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -316,6 +316,7 @@ typedef int __bitwise __kernel_rwf_t;
 #define PAGE_IS_SWAPPED		(1 << 4)
 #define PAGE_IS_PFNZERO		(1 << 5)
 #define PAGE_IS_HUGE		(1 << 6)
+#define PAGE_IS_SOFT_DIRTY	(1 << 7)
 
 /*
  * struct page_region - Page region with flags
-- 
2.42.0.869.gea05f2083d-goog

[PATCH 2/2] selftests/mm: check that PAGEMAP_SCAN returns correct categories

[Andrei Vagin]

Right now, tests read page flags from /proc/pid/pagemap files. With this
change, tests will check that PAGEMAP_SCAN return correct information
too.

Signed-off-by: Andrei Vagin <avagin@google.com>
---
 tools/testing/selftests/mm/vm_util.c | 53 ++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 3082b40492dd..ec3478b96e4c 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -4,6 +4,7 @@
 #include <dirent.h>
 #include <sys/ioctl.h>
 #include <linux/userfaultfd.h>
+#include <linux/fs.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 #include "../kselftest.h"
@@ -28,19 +29,65 @@ uint64_t pagemap_get_entry(int fd, char *start)
 	return entry;
 }
 
+static uint64_t pagemap_scan_get_categories(int fd, char *start)
+{
+	struct pm_scan_arg arg;
+	struct page_region r;
+	long ret;
+
+	arg.start = (uintptr_t)start;
+	arg.end = (uintptr_t)(start + psize());
+	arg.vec = (uintptr_t)&r;
+	arg.vec_len = 1;
+	arg.flags = 0;
+	arg.size = sizeof(struct pm_scan_arg);
+	arg.max_pages = 0;
+	arg.category_inverted = 0;
+	arg.category_mask = 0;
+	arg.category_anyof_mask = PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | PAGE_IS_FILE |
+				  PAGE_IS_PRESENT | PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |
+				  PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY;
+	arg.return_mask = arg.category_anyof_mask;
+
+	ret = ioctl(fd, PAGEMAP_SCAN, &arg);
+	if (ret < 0)
+		ksft_exit_fail_msg("PAGEMAP_SCAN failed: %s\n", strerror(errno));
+	if (ret == 0)
+		return 0;
+	return r.categories;
+}
+
+static bool page_entry_is(int fd, char *start, char *desc,
+			  uint64_t pagemap_flags, uint64_t pagescan_flags)
+{
+	bool m, s;
+
+	m = pagemap_get_entry(fd, start) & pagemap_flags;
+	s = pagemap_scan_get_categories(fd, start) & pagescan_flags;
+	if (m == s)
+		return m;
+
+	ksft_exit_fail_msg(
+		"read and ioctl return unmatched results for %s: %d %d", desc, m, s);
+	return m;
+}
+
 bool pagemap_is_softdirty(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & PM_SOFT_DIRTY;
+	return page_entry_is(fd, start, "soft-dirty",
+				PM_SOFT_DIRTY, PAGE_IS_SOFT_DIRTY);
 }
 
 bool pagemap_is_swapped(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & PM_SWAP;
+	return page_entry_is(fd, start, "swap", PM_SWAP, PAGE_IS_SWAPPED);
 }
 
 bool pagemap_is_populated(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & (PM_PRESENT | PM_SWAP);
+	return page_entry_is(fd, start, "populated",
+				PM_PRESENT | PM_SWAP,
+				PAGE_IS_PRESENT | PAGE_IS_SWAPPED);
 }
 
 unsigned long pagemap_get_pfn(int fd, char *start)
-- 
2.42.0.869.gea05f2083d-goog

Re: [PATCH 1/2 v2] fs/proc/task_mmu: report SOFT_DIRTY bits through the PAGEMAP_SCAN ioctl

[Muhammad Usama Anjum]

On 11/7/23 3:09 AM, Andrei Vagin wrote:
> The PAGEMAP_SCAN ioctl returns information regarding page table entries.
> It is more efficient compared to reading pagemap files. CRIU can start
> to utilize this ioctl, but it needs info about soft-dirty bits to track
> memory changes.
> 
> We are aware of a new method for tracking memory changes implemented in
> the PAGEMAP_SCAN ioctl. For CRIU, the primary advantage of this method
> is its usability by unprivileged users. However, it is not feasible to
> transparently replace the soft-dirty tracker with the new one. The main
> problem here is userfault descriptors that have to be preserved between
> pre-dump iterations.  It means criu continues supporting the soft-dirty
> method to avoid breakage for current users. The new method will be
> implemented as a separate feature.
> 
> Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
> Cc: Michał Mirosław <mirq-linux@rere.qmqm.pl>
> Signed-off-by: Andrei Vagin <avagin@google.com>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>

> ---
> v2: check the soft-dirty bit in pagemap_page_category
> 
>  Documentation/admin-guide/mm/pagemap.rst |  1 +
>  fs/proc/task_mmu.c                       | 17 ++++++++++++++++-
>  include/uapi/linux/fs.h                  |  1 +
>  3 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
> index fe17cf210426..f5f065c67615 100644
> --- a/Documentation/admin-guide/mm/pagemap.rst
> +++ b/Documentation/admin-guide/mm/pagemap.rst
> @@ -253,6 +253,7 @@ Following flags about pages are currently supported:
>  - ``PAGE_IS_SWAPPED`` - Page is in swapped
>  - ``PAGE_IS_PFNZERO`` - Page has zero PFN
>  - ``PAGE_IS_HUGE`` - Page is THP or Hugetlb backed
> +- ``PAGE_IS_SOFT_DIRTY`` - Page is soft-dirty
>  
>  The ``struct pm_scan_arg`` is used as the argument of the IOCTL.
>  
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index ef2eb12906da..51e0ec658457 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1761,7 +1761,7 @@ static int pagemap_release(struct inode *inode, struct file *file)
>  #define PM_SCAN_CATEGORIES	(PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN |	\
>  				 PAGE_IS_FILE |	PAGE_IS_PRESENT |	\
>  				 PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |	\
> -				 PAGE_IS_HUGE)
> +				 PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY)
>  #define PM_SCAN_FLAGS		(PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC)
>  
>  struct pagemap_scan_private {
> @@ -1793,6 +1793,8 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
>  
>  		if (is_zero_pfn(pte_pfn(pte)))
>  			categories |= PAGE_IS_PFNZERO;
> +		if (pte_soft_dirty(pte))
> +			categories |= PAGE_IS_SOFT_DIRTY;
>  	} else if (is_swap_pte(pte)) {
>  		swp_entry_t swp;
>  
> @@ -1806,6 +1808,8 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
>  			    !PageAnon(pfn_swap_entry_to_page(swp)))
>  				categories |= PAGE_IS_FILE;
>  		}
> +		if (pte_swp_soft_dirty(pte))
> +			categories |= PAGE_IS_SOFT_DIRTY;
>  	}
>  
>  	return categories;
> @@ -1853,12 +1857,16 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p,
>  
>  		if (is_zero_pfn(pmd_pfn(pmd)))
>  			categories |= PAGE_IS_PFNZERO;
> +		if (pmd_soft_dirty(pmd))
> +			categories |= PAGE_IS_SOFT_DIRTY;
>  	} else if (is_swap_pmd(pmd)) {
>  		swp_entry_t swp;
>  
>  		categories |= PAGE_IS_SWAPPED;
>  		if (!pmd_swp_uffd_wp(pmd))
>  			categories |= PAGE_IS_WRITTEN;
> +		if (pmd_swp_soft_dirty(pmd))
> +			categories |= PAGE_IS_SOFT_DIRTY;
>  
>  		if (p->masks_of_interest & PAGE_IS_FILE) {
>  			swp = pmd_to_swp_entry(pmd);
> @@ -1905,10 +1913,14 @@ static unsigned long pagemap_hugetlb_category(pte_t pte)
>  			categories |= PAGE_IS_FILE;
>  		if (is_zero_pfn(pte_pfn(pte)))
>  			categories |= PAGE_IS_PFNZERO;
> +		if (pte_soft_dirty(pte))
> +			categories |= PAGE_IS_SOFT_DIRTY;
>  	} else if (is_swap_pte(pte)) {
>  		categories |= PAGE_IS_SWAPPED;
>  		if (!pte_swp_uffd_wp_any(pte))
>  			categories |= PAGE_IS_WRITTEN;
> +		if (pte_swp_soft_dirty(pte))
> +			categories |= PAGE_IS_SOFT_DIRTY;
>  	}
>  
>  	return categories;
> @@ -1991,6 +2003,9 @@ static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
>  	if (vma->vm_flags & VM_PFNMAP)
>  		return 1;
>  
> +	if (vma->vm_flags & VM_SOFTDIRTY)
> +		vma_category |= PAGE_IS_SOFT_DIRTY;
> +
>  	if (!pagemap_scan_is_interesting_vma(vma_category, p))
>  		return 1;
>  
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index da43810b7485..48ad69f7722e 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -316,6 +316,7 @@ typedef int __bitwise __kernel_rwf_t;
>  #define PAGE_IS_SWAPPED		(1 << 4)
>  #define PAGE_IS_PFNZERO		(1 << 5)
>  #define PAGE_IS_HUGE		(1 << 6)
> +#define PAGE_IS_SOFT_DIRTY	(1 << 7)
LGTM, other than the missed the identical change in
tools/include/uapi/linux/fs.h as well.

>  
>  /*
>   * struct page_region - Page region with flags

-- 
BR,
Muhammad Usama Anjum

Re: [PATCH 2/2] selftests/mm: check that PAGEMAP_SCAN returns correct categories

[Muhammad Usama Anjum]

On 11/7/23 3:09 AM, Andrei Vagin wrote:
> Right now, tests read page flags from /proc/pid/pagemap files. With this
> change, tests will check that PAGEMAP_SCAN return correct information
> too.
> 
> Signed-off-by: Andrei Vagin <avagin@google.com>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@collabora.com>

> ---
>  tools/testing/selftests/mm/vm_util.c | 53 ++++++++++++++++++++++++++--
>  1 file changed, 50 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> index 3082b40492dd..ec3478b96e4c 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -4,6 +4,7 @@
>  #include <dirent.h>
>  #include <sys/ioctl.h>
>  #include <linux/userfaultfd.h>
> +#include <linux/fs.h>
>  #include <sys/syscall.h>
>  #include <unistd.h>
>  #include "../kselftest.h"
> @@ -28,19 +29,65 @@ uint64_t pagemap_get_entry(int fd, char *start)
>  	return entry;
>  }
>  
> +static uint64_t pagemap_scan_get_categories(int fd, char *start)
> +{
> +	struct pm_scan_arg arg;
> +	struct page_region r;
> +	long ret;
> +
> +	arg.start = (uintptr_t)start;
> +	arg.end = (uintptr_t)(start + psize());
> +	arg.vec = (uintptr_t)&r;
> +	arg.vec_len = 1;
> +	arg.flags = 0;
> +	arg.size = sizeof(struct pm_scan_arg);
> +	arg.max_pages = 0;
> +	arg.category_inverted = 0;
> +	arg.category_mask = 0;
> +	arg.category_anyof_mask = PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | PAGE_IS_FILE |
> +				  PAGE_IS_PRESENT | PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |
> +				  PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY;
> +	arg.return_mask = arg.category_anyof_mask;
> +
> +	ret = ioctl(fd, PAGEMAP_SCAN, &arg);
> +	if (ret < 0)
> +		ksft_exit_fail_msg("PAGEMAP_SCAN failed: %s\n", strerror(errno));
> +	if (ret == 0)
> +		return 0;
> +	return r.categories;
> +}
> +
> +static bool page_entry_is(int fd, char *start, char *desc,
> +			  uint64_t pagemap_flags, uint64_t pagescan_flags)
> +{
> +	bool m, s;
> +
> +	m = pagemap_get_entry(fd, start) & pagemap_flags;
> +	s = pagemap_scan_get_categories(fd, start) & pagescan_flags;
> +	if (m == s)
> +		return m;
> +
> +	ksft_exit_fail_msg(
> +		"read and ioctl return unmatched results for %s: %d %d", desc, m, s);
> +	return m;
> +}
> +
>  bool pagemap_is_softdirty(int fd, char *start)
>  {
> -	return pagemap_get_entry(fd, start) & PM_SOFT_DIRTY;
> +	return page_entry_is(fd, start, "soft-dirty",
> +				PM_SOFT_DIRTY, PAGE_IS_SOFT_DIRTY);
>  }
>  
>  bool pagemap_is_swapped(int fd, char *start)
>  {
> -	return pagemap_get_entry(fd, start) & PM_SWAP;
> +	return page_entry_is(fd, start, "swap", PM_SWAP, PAGE_IS_SWAPPED);
>  }
>  
>  bool pagemap_is_populated(int fd, char *start)
>  {
> -	return pagemap_get_entry(fd, start) & (PM_PRESENT | PM_SWAP);
> +	return page_entry_is(fd, start, "populated",
> +				PM_PRESENT | PM_SWAP,
> +				PAGE_IS_PRESENT | PAGE_IS_SWAPPED);
>  }
>  
>  unsigned long pagemap_get_pfn(int fd, char *start)

-- 
BR,
Muhammad Usama Anjum

Re: [PATCH 2/2] selftests/mm: check that PAGEMAP_SCAN returns correct categories

[Ryan Roberts]

On 06/11/2023 22:09, Andrei Vagin wrote:
> Right now, tests read page flags from /proc/pid/pagemap files. With this
> change, tests will check that PAGEMAP_SCAN return correct information
> too.
> 
> Signed-off-by: Andrei Vagin <avagin@google.com>
> ---
>  tools/testing/selftests/mm/vm_util.c | 53 ++++++++++++++++++++++++++--
>  1 file changed, 50 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> index 3082b40492dd..ec3478b96e4c 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -4,6 +4,7 @@
>  #include <dirent.h>
>  #include <sys/ioctl.h>
>  #include <linux/userfaultfd.h>
> +#include <linux/fs.h>
>  #include <sys/syscall.h>
>  #include <unistd.h>
>  #include "../kselftest.h"
> @@ -28,19 +29,65 @@ uint64_t pagemap_get_entry(int fd, char *start)
>  	return entry;
>  }
>  
> +static uint64_t pagemap_scan_get_categories(int fd, char *start)
> +{
> +	struct pm_scan_arg arg;
> +	struct page_region r;
> +	long ret;
> +
> +	arg.start = (uintptr_t)start;
> +	arg.end = (uintptr_t)(start + psize());
> +	arg.vec = (uintptr_t)&r;
> +	arg.vec_len = 1;
> +	arg.flags = 0;
> +	arg.size = sizeof(struct pm_scan_arg);
> +	arg.max_pages = 0;
> +	arg.category_inverted = 0;
> +	arg.category_mask = 0;
> +	arg.category_anyof_mask = PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | PAGE_IS_FILE |
> +				  PAGE_IS_PRESENT | PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |
> +				  PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY;
> +	arg.return_mask = arg.category_anyof_mask;
> +
> +	ret = ioctl(fd, PAGEMAP_SCAN, &arg);
> +	if (ret < 0)
> +		ksft_exit_fail_msg("PAGEMAP_SCAN failed: %s\n", strerror(errno));

FYI, when run against kernel v6.7-rc1, this fails with EINVAL. I'm guessing
you've added this as part of testing an extension to this ABI and its only
present in mm-unstable?

I believe that normally we try to keep selftests backwards compatible so they
run on older kernels (a feature I rely on). As a result 3 or so test suites are
immediately failing (inc cow). Can this be fixed to fallback to old behaviour
gracefully in this case?

Thanks,
Ryan


> +	if (ret == 0)
> +		return 0;
> +	return r.categories;
> +}
> +
> +static bool page_entry_is(int fd, char *start, char *desc,
> +			  uint64_t pagemap_flags, uint64_t pagescan_flags)
> +{
> +	bool m, s;
> +
> +	m = pagemap_get_entry(fd, start) & pagemap_flags;
> +	s = pagemap_scan_get_categories(fd, start) & pagescan_flags;
> +	if (m == s)
> +		return m;
> +
> +	ksft_exit_fail_msg(
> +		"read and ioctl return unmatched results for %s: %d %d", desc, m, s);
> +	return m;
> +}
> +
>  bool pagemap_is_softdirty(int fd, char *start)
>  {
> -	return pagemap_get_entry(fd, start) & PM_SOFT_DIRTY;
> +	return page_entry_is(fd, start, "soft-dirty",
> +				PM_SOFT_DIRTY, PAGE_IS_SOFT_DIRTY);
>  }
>  
>  bool pagemap_is_swapped(int fd, char *start)
>  {
> -	return pagemap_get_entry(fd, start) & PM_SWAP;
> +	return page_entry_is(fd, start, "swap", PM_SWAP, PAGE_IS_SWAPPED);
>  }
>  
>  bool pagemap_is_populated(int fd, char *start)
>  {
> -	return pagemap_get_entry(fd, start) & (PM_PRESENT | PM_SWAP);
> +	return page_entry_is(fd, start, "populated",
> +				PM_PRESENT | PM_SWAP,
> +				PAGE_IS_PRESENT | PAGE_IS_SWAPPED);
>  }
>  
>  unsigned long pagemap_get_pfn(int fd, char *start)

[PATCH 2/2] selftests/mm: check that PAGEMAP_SCAN returns correct categories

[Andrei Vagin]

Right now, tests read page flags from /proc/pid/pagemap files. With this
change, tests will check that PAGEMAP_SCAN return correct information
too.

Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Andrei Vagin <avagin@google.com>
---
 tools/testing/selftests/mm/vm_util.c | 53 ++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 3082b40492dd..ec3478b96e4c 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -4,6 +4,7 @@
 #include <dirent.h>
 #include <sys/ioctl.h>
 #include <linux/userfaultfd.h>
+#include <linux/fs.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 #include "../kselftest.h"
@@ -28,19 +29,65 @@ uint64_t pagemap_get_entry(int fd, char *start)
 	return entry;
 }
 
+static uint64_t pagemap_scan_get_categories(int fd, char *start)
+{
+	struct pm_scan_arg arg;
+	struct page_region r;
+	long ret;
+
+	arg.start = (uintptr_t)start;
+	arg.end = (uintptr_t)(start + psize());
+	arg.vec = (uintptr_t)&r;
+	arg.vec_len = 1;
+	arg.flags = 0;
+	arg.size = sizeof(struct pm_scan_arg);
+	arg.max_pages = 0;
+	arg.category_inverted = 0;
+	arg.category_mask = 0;
+	arg.category_anyof_mask = PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | PAGE_IS_FILE |
+				  PAGE_IS_PRESENT | PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |
+				  PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY;
+	arg.return_mask = arg.category_anyof_mask;
+
+	ret = ioctl(fd, PAGEMAP_SCAN, &arg);
+	if (ret < 0)
+		ksft_exit_fail_msg("PAGEMAP_SCAN failed: %s\n", strerror(errno));
+	if (ret == 0)
+		return 0;
+	return r.categories;
+}
+
+static bool page_entry_is(int fd, char *start, char *desc,
+			  uint64_t pagemap_flags, uint64_t pagescan_flags)
+{
+	bool m, s;
+
+	m = pagemap_get_entry(fd, start) & pagemap_flags;
+	s = pagemap_scan_get_categories(fd, start) & pagescan_flags;
+	if (m == s)
+		return m;
+
+	ksft_exit_fail_msg(
+		"read and ioctl return unmatched results for %s: %d %d", desc, m, s);
+	return m;
+}
+
 bool pagemap_is_softdirty(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & PM_SOFT_DIRTY;
+	return page_entry_is(fd, start, "soft-dirty",
+				PM_SOFT_DIRTY, PAGE_IS_SOFT_DIRTY);
 }
 
 bool pagemap_is_swapped(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & PM_SWAP;
+	return page_entry_is(fd, start, "swap", PM_SWAP, PAGE_IS_SWAPPED);
 }
 
 bool pagemap_is_populated(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & (PM_PRESENT | PM_SWAP);
+	return page_entry_is(fd, start, "populated",
+				PM_PRESENT | PM_SWAP,
+				PAGE_IS_PRESENT | PAGE_IS_SWAPPED);
 }
 
 unsigned long pagemap_get_pfn(int fd, char *start)
-- 
2.42.0.869.gea05f2083d-goog