diff mbox series

[v32,2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs

Message ID 20230816113049.1697849-3-usama.anjum@collabora.com (mailing list archive)
State New
Headers show
Series Implement IOCTL to get and optionally clear info about PTEs | expand

Commit Message

Muhammad Usama Anjum Aug. 16, 2023, 11:30 a.m. UTC
The PAGEMAP_SCAN IOCTL on the pagemap file can be used to get or optionally
clear the info about page table entries. The following operations are
supported in this IOCTL:
- Scan the address range and get the memory ranges matching the provided
  criteria. This is performed when the output buffer is specified.
- Write-protect the pages. The PM_SCAN_WP_MATCHING is used to write-protect
  the pages of interest. The PM_SCAN_CHECK_WPASYNC aborts the operation if
  non-Async Write Protected pages are found. The ``PM_SCAN_WP_MATCHING``
  can be used with or without PM_SCAN_CHECK_WPASYNC.
- Both of those operations can be combined into one atomic operation where
  we can get and write protect the pages as well.

Following flags about pages are currently supported:
- PAGE_IS_WPALLOWED - Page has async-write-protection enabled
- PAGE_IS_WRITTEN - Page has been written to from the time it was write protected
- PAGE_IS_FILE - Page is file backed
- PAGE_IS_PRESENT - Page is present in the memory
- PAGE_IS_SWAPPED - Page is in swapped
- PAGE_IS_PFNZERO - Page has zero PFN
- PAGE_IS_HUGE - Page is THP or Hugetlb backed

This IOCTL can be extended to get information about more PTE bits. The
entire address range passed by user [start, end) is scanned until either
the user provided buffer is full or max_pages have been found.

Reviewed-by: Andrei Vagin <avagin@gmail.com>
Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
---
Chagnes in v32:
- Remove un-needed if condition to set walk_end address

Changes in v31:
- Remove walk_end_addr
- Fix build warning by typecasting u64 variables to long first before
  casting them to void *

Changes in v30:
- Minor nitpicks

Changes in v29:
- Cosmetic changes
- Add and improve comments
- Remove cur_buf as merging members issue has been removed

Changes in v28:
- Fix walk_end one last time after doing through testing

Changes in v27:
- Add PAGE_IS_HUGE
- Iterate until temporary buffer is full to do less iterations
- Don't check if PAGE_IS_FILE if no mask needs it as it is very
  expensive to check per pte
- bring is_interesting_page() outside pagemap_scan_output() to remove
  the horrible return value check
- Replace memcpy() with direct copy
- rename end_addr to walk_end_addr in pagemap_scan_private
- Abort walk if fatal_signal_pending()

Changes in v26:
Changes made by Usama:
- Fix the wrong breaking of loop if page isn't interesting, skip intsead
- Untag the address and save them into struct
- Round off the end address to next page
- Correct the partial hugetlb page handling and returning the error
- Rename PAGE_IS_WPASYNC to PAGE_IS_WPALLOWED
- Return walk ending address in walk_end instead of returning in start
  as there is potential of replacing the memory tag

Changes by Michał:
1. the API:
  a. return ranges as {begin, end} instead of {begin + len};
  b. rename match "flags" to 'page categories' everywhere - this makes
	it easier to differentiate the ioctl()s categorisation of pages
	from struct page flags;
  c. change {required + excluded} to {inverted + required}. This was
	rejected before, but I'd like to illustrate the difference.
	Old interface can be translated to the new by:
		categories_inverted = excluded_mask
		categories_mask = required_mask | excluded_mask
		categories_anyof_mask = anyof_mask
	The new way allows filtering by: A & (B | !C)
		categories_inverted = C
		categories_mask = A
		categories_anyof_mask = B | C
  e. allow no-op calls
2. the implementation:
  a. gather the page-categorising and write-protecting code in one place;
  b. optimization: add whole-vma skipping for WP usecase;
  c. extracted output limiting code to pagemap_scan_output();
  d. extracted range coalescing to pagemap_scan_push_range();
  e. extracted THP entry handling to pagemap_scan_thp_entry();
  f. added a shortcut for non-WP hugetlb scan; avoids conditional
	locking;
  g. extracted scan buffer handling code out of do_pagemap_scan();
  h. rework output code to always try to write pending ranges; if EFAULT
	is generated it always overwrites the original error code;
	(the case of SIGKILL is needlessly trying to write the output
	now, but this should be rare case and ignoring it makes the code
	not needing a goto)
3.Change no-GET operation condition from `arg.return_mask == 0` to
  `arg.vec == NULL`. This will allow issuing the ioctl with
  return_mask == 0 to gather matching ranges when the exact category
  is not interesting. (Anticipated for CRIU scanning a large sparse
  anonymous mapping).

Changes in v25:
- Do proper filtering on hole as well (hole got missed earlier)

Changes in v24:
- Place WP markers in case of hole as well

Changes in v23:
- Set vec_buf_index to 0 only when vec_buf_index is set
- Return -EFAULT instead of -EINVAL if vec is NULL
- Correctly return the walk ending address to the page granularity

Changes in v22:
- Interface change to return walk ending address to user:
  - Replace [start start + len) with [start, end)
  - Return the ending address of the address walk in start

Changes in v21:
- Abort walk instead of returning error if WP is to be performed on
  partial hugetlb
- Changed the data types of some variables in pagemap_scan_private to
  long

Changes in v20:
- Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO

Changes in v19:
- Interface changes such as renaming, return mask and WP can be used
  with any flags specified in masks
- Internal code changes

Changes in v18:
- Rebased on top of next-20230613
  - ptep_get() updates
  - remove pmd_trans_unstable() and add ACTION_AGAIN
- Review updates (Micheal)

Changes in v17:
- Rebased on next-20230606
- Made make_uffd_wp_*_pte() better and minor changes

Changes in v16:
- Fixed a corner case where kernel writes beyond user buffer by one
  element
- Bring back exclusive PM_SCAN_OP_WP
- Cosmetic changes

Changes in v15:
- Build fix:
  - Use generic tlb flush function in pagemap_scan_pmd_entry() instead of
    using x86 specific flush function in do_pagemap_scan()
  - Remove #ifdef from pagemap_scan_hugetlb_entry()
  - Use mm instead of undefined vma->vm_mm

Changes in v14:
- Fix build error caused by #ifdef added at last minute in some configs

Changes in v13:
- Review updates
- mmap_read_lock_killable() instead of mmap_read_lock()
- Replace uffd_wp_range() with helpers which increases performance
  drastically for OP_WP operations by reducing the number of tlb
  flushing etc
- Add MMU_NOTIFY_PROTECTION_VMA notification for the memory range

Changes in v12:
- Add hugetlb support to cover all memory types
- Merge "userfaultfd: Define dummy uffd_wp_range()" with this patch
- Review updates to the code

Changes in v11:
- Find written pages in a better way
- Fix a corner case (thanks Paul)
- Improve the code/comments
- remove ENGAGE_WP + ! GET operation
- shorten the commit message in favour of moving documentation to
  pagemap.rst

Changes in v10:
- move changes in tools/include/uapi/linux/fs.h to separate patch
- update commit message

Change in v8:
- Correct is_pte_uffd_wp()
- Improve readability and error checks
- Remove some un-needed code

Changes in v7:
- Rebase on top of latest next
- Fix some corner cases
- Base soft-dirty on the uffd wp async
- Update the terminologies
- Optimize the memory usage inside the ioctl
---
 fs/proc/task_mmu.c            | 669 ++++++++++++++++++++++++++++++++++
 include/linux/hugetlb.h       |   1 +
 include/linux/userfaultfd_k.h |   7 +
 include/uapi/linux/fs.h       |  59 +++
 mm/hugetlb.c                  |   2 +-
 5 files changed, 737 insertions(+), 1 deletion(-)

Comments

kernel test robot Aug. 18, 2023, 7:16 a.m. UTC | #1
Hi Muhammad,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on next-20230817]
[cannot apply to linus/master v6.5-rc6]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Muhammad-Usama-Anjum/userfaultfd-UFFD_FEATURE_WP_ASYNC/20230816-193454
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20230816113049.1697849-3-usama.anjum%40collabora.com
patch subject: [PATCH v32 2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20230818/202308181520.yCq9Z26w-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 12.3.0
reproduce: (https://download.01.org/0day-ci/archive/20230818/202308181520.yCq9Z26w-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308181520.yCq9Z26w-lkp@intel.com/

All errors (new ones prefixed by >>):

   fs/proc/task_mmu.c: In function 'pagemap_scan_thp_entry':
>> fs/proc/task_mmu.c:2077:28: error: 'HPAGE_SIZE' undeclared (first use in this function); did you mean 'PAGE_SIZE'?
    2077 |         if (end != start + HPAGE_SIZE) {
         |                            ^~~~~~~~~~
         |                            PAGE_SIZE
   fs/proc/task_mmu.c:2077:28: note: each undeclared identifier is reported only once for each function it appears in


vim +2077 fs/proc/task_mmu.c

  2044	
  2045	static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start,
  2046					  unsigned long end, struct mm_walk *walk)
  2047	{
  2048	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
  2049		struct pagemap_scan_private *p = walk->private;
  2050		struct vm_area_struct *vma = walk->vma;
  2051		unsigned long categories;
  2052		spinlock_t *ptl;
  2053		int ret = 0;
  2054	
  2055		ptl = pmd_trans_huge_lock(pmd, vma);
  2056		if (!ptl)
  2057			return -ENOENT;
  2058	
  2059		categories = p->cur_vma_category | pagemap_thp_category(*pmd);
  2060	
  2061		if (!pagemap_scan_is_interesting_page(categories, p))
  2062			goto out_unlock;
  2063	
  2064		ret = pagemap_scan_output(categories, p, start, &end);
  2065		if (start == end)
  2066			goto out_unlock;
  2067	
  2068		if (~p->arg.flags & PM_SCAN_WP_MATCHING)
  2069			goto out_unlock;
  2070		if (~categories & PAGE_IS_WRITTEN)
  2071			goto out_unlock;
  2072	
  2073		/*
  2074		 * Break huge page into small pages if the WP operation
  2075		 * needs to be performed on a portion of the huge page.
  2076		 */
> 2077		if (end != start + HPAGE_SIZE) {
  2078			spin_unlock(ptl);
  2079			split_huge_pmd(vma, pmd, start);
  2080			pagemap_scan_backout_range(p, start, end);
  2081			/* Report as if there was no THP */
  2082			return -ENOENT;
  2083		}
  2084	
  2085		make_uffd_wp_pmd(vma, start, pmd);
  2086		flush_tlb_range(vma, start, end);
  2087	out_unlock:
  2088		spin_unlock(ptl);
  2089		return ret;
  2090	#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
  2091		return -ENOENT;
  2092	#endif
  2093	}
  2094
Muhammad Usama Anjum Aug. 18, 2023, 9:55 a.m. UTC | #2
On 8/18/23 12:16 PM, kernel test robot wrote:
> Hi Muhammad,
> 
> kernel test robot noticed the following build errors:
> 
> [auto build test ERROR on akpm-mm/mm-everything]
> [also build test ERROR on next-20230817]
> [cannot apply to linus/master v6.5-rc6]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Muhammad-Usama-Anjum/userfaultfd-UFFD_FEATURE_WP_ASYNC/20230816-193454
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> patch link:    https://lore.kernel.org/r/20230816113049.1697849-3-usama.anjum%40collabora.com
> patch subject: [PATCH v32 2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs
> config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20230818/202308181520.yCq9Z26w-lkp@intel.com/config)
> compiler: arceb-elf-gcc (GCC) 12.3.0
> reproduce: (https://download.01.org/0day-ci/archive/20230818/202308181520.yCq9Z26w-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202308181520.yCq9Z26w-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    fs/proc/task_mmu.c: In function 'pagemap_scan_thp_entry':
>>> fs/proc/task_mmu.c:2077:28: error: 'HPAGE_SIZE' undeclared (first use in this function); did you mean 'PAGE_SIZE'?
>     2077 |         if (end != start + HPAGE_SIZE) {
>          |                            ^~~~~~~~~~
>          |                            PAGE_SIZE
I've been emailing arc maintainers for resolution of this error from April,
but nobody replies there:
https://lore.kernel.org/all/0e6b318a-bbf8-3701-00af-1802c6347897@collabora.com

>    fs/proc/task_mmu.c:2077:28: note: each undeclared identifier is reported only once for each function it appears in
> 
> 
> vim +2077 fs/proc/task_mmu.c
> 
>   2044	
>   2045	static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start,
>   2046					  unsigned long end, struct mm_walk *walk)
>   2047	{
>   2048	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>   2049		struct pagemap_scan_private *p = walk->private;
>   2050		struct vm_area_struct *vma = walk->vma;
>   2051		unsigned long categories;
>   2052		spinlock_t *ptl;
>   2053		int ret = 0;
>   2054	
>   2055		ptl = pmd_trans_huge_lock(pmd, vma);
>   2056		if (!ptl)
>   2057			return -ENOENT;
>   2058	
>   2059		categories = p->cur_vma_category | pagemap_thp_category(*pmd);
>   2060	
>   2061		if (!pagemap_scan_is_interesting_page(categories, p))
>   2062			goto out_unlock;
>   2063	
>   2064		ret = pagemap_scan_output(categories, p, start, &end);
>   2065		if (start == end)
>   2066			goto out_unlock;
>   2067	
>   2068		if (~p->arg.flags & PM_SCAN_WP_MATCHING)
>   2069			goto out_unlock;
>   2070		if (~categories & PAGE_IS_WRITTEN)
>   2071			goto out_unlock;
>   2072	
>   2073		/*
>   2074		 * Break huge page into small pages if the WP operation
>   2075		 * needs to be performed on a portion of the huge page.
>   2076		 */
>> 2077		if (end != start + HPAGE_SIZE) {
>   2078			spin_unlock(ptl);
>   2079			split_huge_pmd(vma, pmd, start);
>   2080			pagemap_scan_backout_range(p, start, end);
>   2081			/* Report as if there was no THP */
>   2082			return -ENOENT;
>   2083		}
>   2084	
>   2085		make_uffd_wp_pmd(vma, start, pmd);
>   2086		flush_tlb_range(vma, start, end);
>   2087	out_unlock:
>   2088		spin_unlock(ptl);
>   2089		return ret;
>   2090	#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
>   2091		return -ENOENT;
>   2092	#endif
>   2093	}
>   2094	
>
Philip Li Aug. 18, 2023, 12:35 p.m. UTC | #3
On Fri, Aug 18, 2023 at 02:55:36PM +0500, Muhammad Usama Anjum wrote:
> On 8/18/23 12:16 PM, kernel test robot wrote:
> > Hi Muhammad,
> > 
> > kernel test robot noticed the following build errors:
> > 
> > [auto build test ERROR on akpm-mm/mm-everything]
> > [also build test ERROR on next-20230817]
> > [cannot apply to linus/master v6.5-rc6]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> > 
> > url:    https://github.com/intel-lab-lkp/linux/commits/Muhammad-Usama-Anjum/userfaultfd-UFFD_FEATURE_WP_ASYNC/20230816-193454
> > base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> > patch link:    https://lore.kernel.org/r/20230816113049.1697849-3-usama.anjum%40collabora.com
> > patch subject: [PATCH v32 2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs
> > config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20230818/202308181520.yCq9Z26w-lkp@intel.com/config)
> > compiler: arceb-elf-gcc (GCC) 12.3.0
> > reproduce: (https://download.01.org/0day-ci/archive/20230818/202308181520.yCq9Z26w-lkp@intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202308181520.yCq9Z26w-lkp@intel.com/
> > 
> > All errors (new ones prefixed by >>):
> > 
> >    fs/proc/task_mmu.c: In function 'pagemap_scan_thp_entry':
> >>> fs/proc/task_mmu.c:2077:28: error: 'HPAGE_SIZE' undeclared (first use in this function); did you mean 'PAGE_SIZE'?
> >     2077 |         if (end != start + HPAGE_SIZE) {
> >          |                            ^~~~~~~~~~
> >          |                            PAGE_SIZE
> I've been emailing arc maintainers for resolution of this error from April,
> but nobody replies there:
> https://lore.kernel.org/all/0e6b318a-bbf8-3701-00af-1802c6347897@collabora.com

Thanks for the info, we will update the bot to ignore this error
to avoid duplicated reports.

> 
> >    fs/proc/task_mmu.c:2077:28: note: each undeclared identifier is reported only once for each function it appears in
> > 
> > 
> > vim +2077 fs/proc/task_mmu.c
> > 
> >   2044	
> >   2045	static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start,
> >   2046					  unsigned long end, struct mm_walk *walk)
> >   2047	{
> >   2048	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >   2049		struct pagemap_scan_private *p = walk->private;
> >   2050		struct vm_area_struct *vma = walk->vma;
> >   2051		unsigned long categories;
> >   2052		spinlock_t *ptl;
> >   2053		int ret = 0;
> >   2054	
> >   2055		ptl = pmd_trans_huge_lock(pmd, vma);
> >   2056		if (!ptl)
> >   2057			return -ENOENT;
> >   2058	
> >   2059		categories = p->cur_vma_category | pagemap_thp_category(*pmd);
> >   2060	
> >   2061		if (!pagemap_scan_is_interesting_page(categories, p))
> >   2062			goto out_unlock;
> >   2063	
> >   2064		ret = pagemap_scan_output(categories, p, start, &end);
> >   2065		if (start == end)
> >   2066			goto out_unlock;
> >   2067	
> >   2068		if (~p->arg.flags & PM_SCAN_WP_MATCHING)
> >   2069			goto out_unlock;
> >   2070		if (~categories & PAGE_IS_WRITTEN)
> >   2071			goto out_unlock;
> >   2072	
> >   2073		/*
> >   2074		 * Break huge page into small pages if the WP operation
> >   2075		 * needs to be performed on a portion of the huge page.
> >   2076		 */
> >> 2077		if (end != start + HPAGE_SIZE) {
> >   2078			spin_unlock(ptl);
> >   2079			split_huge_pmd(vma, pmd, start);
> >   2080			pagemap_scan_backout_range(p, start, end);
> >   2081			/* Report as if there was no THP */
> >   2082			return -ENOENT;
> >   2083		}
> >   2084	
> >   2085		make_uffd_wp_pmd(vma, start, pmd);
> >   2086		flush_tlb_range(vma, start, end);
> >   2087	out_unlock:
> >   2088		spin_unlock(ptl);
> >   2089		return ret;
> >   2090	#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
> >   2091		return -ENOENT;
> >   2092	#endif
> >   2093	}
> >   2094	
> > 
> 
> -- 
> BR,
> Muhammad Usama Anjum
>
Michał Mirosław Aug. 19, 2023, 1:04 a.m. UTC | #4
On Wed, Aug 16, 2023 at 04:30:45PM +0500, Muhammad Usama Anjum wrote:
> The PAGEMAP_SCAN IOCTL on the pagemap file can be used to get or optionally
> clear the info about page table entries.
[...]
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
[...]
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +static unsigned long pagemap_thp_category(pmd_t pmd)
> +{
> +	unsigned long categories = PAGE_IS_HUGE;
> +
> +	/*
> +	 * THPs don't support file-backed memory. So PAGE_IS_FILE
> +	 * is not checked here.
> +	 */

It seems that we can have THP for files: ref. recent LKML thread [1].

[1] https://lkml.org/lkml/2023/8/16/1212

> +	if (pmd_present(pmd)) {
> +		categories |= PAGE_IS_PRESENT;
> +		if (!pmd_uffd_wp(pmd))
> +			categories |= PAGE_IS_WRITTEN;
> +		if (is_zero_pfn(pmd_pfn(pmd)))
> +			categories |= PAGE_IS_PFNZERO;
> +	} else if (is_swap_pmd(pmd)) {
> +		categories |= PAGE_IS_SWAPPED;
> +		if (!pmd_swp_uffd_wp(pmd))
> +			categories |= PAGE_IS_WRITTEN;
> +	}
> +
> +	return categories;
> +}

Best Regards
Michał Mirosław
Muhammad Usama Anjum Aug. 21, 2023, 2:11 p.m. UTC | #5
On 8/19/23 6:04 AM, Michał Mirosław wrote:
> On Wed, Aug 16, 2023 at 04:30:45PM +0500, Muhammad Usama Anjum wrote:
>> The PAGEMAP_SCAN IOCTL on the pagemap file can be used to get or optionally
>> clear the info about page table entries.
> [...]
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
> [...]
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> +static unsigned long pagemap_thp_category(pmd_t pmd)
>> +{
>> +	unsigned long categories = PAGE_IS_HUGE;
>> +
>> +	/*
>> +	 * THPs don't support file-backed memory. So PAGE_IS_FILE
>> +	 * is not checked here.
>> +	 */
> 
> It seems that we can have THP for files: ref. recent LKML thread [1].
> 
> [1] https://lkml.org/lkml/2023/8/16/1212
I didn't know about this. It seems like khugepaged can create file THPs.
Not sure if there is direct way to create file backed THPs. Maybe they'll
add this support after adding writing support to these file backed THPs.
READ_ONLY_THP_FOR_FS mentions this.

I can add a few lines of code for this here.

> 
>> +	if (pmd_present(pmd)) {
>> +		categories |= PAGE_IS_PRESENT;
>> +		if (!pmd_uffd_wp(pmd))
>> +			categories |= PAGE_IS_WRITTEN;
>> +		if (is_zero_pfn(pmd_pfn(pmd)))
>> +			categories |= PAGE_IS_PFNZERO;
>> +	} else if (is_swap_pmd(pmd)) {
>> +		categories |= PAGE_IS_SWAPPED;
>> +		if (!pmd_swp_uffd_wp(pmd))
>> +			categories |= PAGE_IS_WRITTEN;
>> +	}
>> +
>> +	return categories;
>> +}
> 
> Best Regards
> Michał Mirosław
diff mbox series

Patch

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4fba49bf09447..0903e10e5fc08 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -19,6 +19,8 @@ 
 #include <linux/shmem_fs.h>
 #include <linux/uaccess.h>
 #include <linux/pkeys.h>
+#include <linux/minmax.h>
+#include <linux/overflow.h>
 
 #include <asm/elf.h>
 #include <asm/tlb.h>
@@ -1760,11 +1762,678 @@  static int pagemap_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+#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)
+#define PM_SCAN_FLAGS		(PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC)
+
+struct pagemap_scan_private {
+	struct pm_scan_arg arg;
+	unsigned long masks_of_interest, cur_vma_category;
+	struct page_region *vec_buf;
+	unsigned long vec_buf_len, vec_buf_index, found_pages;
+	struct page_region __user *vec_out;
+};
+
+static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
+					   struct vm_area_struct *vma,
+					   unsigned long addr, pte_t pte)
+{
+	unsigned long categories = 0;
+
+	if (pte_present(pte)) {
+		struct page *page;
+
+		categories |= PAGE_IS_PRESENT;
+		if (!pte_uffd_wp(pte))
+			categories |= PAGE_IS_WRITTEN;
+
+		if (p->masks_of_interest & PAGE_IS_FILE) {
+			page = vm_normal_page(vma, addr, pte);
+			if (page && !PageAnon(page))
+				categories |= PAGE_IS_FILE;
+		}
+
+		if (is_zero_pfn(pte_pfn(pte)))
+			categories |= PAGE_IS_PFNZERO;
+	} else if (is_swap_pte(pte)) {
+		swp_entry_t swp;
+
+		categories |= PAGE_IS_SWAPPED;
+		if (!pte_swp_uffd_wp_any(pte))
+			categories |= PAGE_IS_WRITTEN;
+
+		if (p->masks_of_interest & PAGE_IS_FILE) {
+			swp = pte_to_swp_entry(pte);
+			if (is_pfn_swap_entry(swp) &&
+			    !PageAnon(pfn_swap_entry_to_page(swp)))
+				categories |= PAGE_IS_FILE;
+		}
+	}
+
+	return categories;
+}
+
+static void make_uffd_wp_pte(struct vm_area_struct *vma,
+			     unsigned long addr, pte_t *pte)
+{
+	pte_t ptent = ptep_get(pte);
+
+	if (pte_present(ptent)) {
+		pte_t old_pte;
+
+		old_pte = ptep_modify_prot_start(vma, addr, pte);
+		ptent = pte_mkuffd_wp(ptent);
+		ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);
+	} else if (is_swap_pte(ptent)) {
+		ptent = pte_swp_mkuffd_wp(ptent);
+		set_pte_at(vma->vm_mm, addr, pte, ptent);
+	} else {
+		set_pte_at(vma->vm_mm, addr, pte,
+			   make_pte_marker(PTE_MARKER_UFFD_WP));
+	}
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static unsigned long pagemap_thp_category(pmd_t pmd)
+{
+	unsigned long categories = PAGE_IS_HUGE;
+
+	/*
+	 * THPs don't support file-backed memory. So PAGE_IS_FILE
+	 * is not checked here.
+	 */
+	if (pmd_present(pmd)) {
+		categories |= PAGE_IS_PRESENT;
+		if (!pmd_uffd_wp(pmd))
+			categories |= PAGE_IS_WRITTEN;
+		if (is_zero_pfn(pmd_pfn(pmd)))
+			categories |= PAGE_IS_PFNZERO;
+	} else if (is_swap_pmd(pmd)) {
+		categories |= PAGE_IS_SWAPPED;
+		if (!pmd_swp_uffd_wp(pmd))
+			categories |= PAGE_IS_WRITTEN;
+	}
+
+	return categories;
+}
+
+static void make_uffd_wp_pmd(struct vm_area_struct *vma,
+			     unsigned long addr, pmd_t *pmdp)
+{
+	pmd_t old, pmd = *pmdp;
+
+	if (pmd_present(pmd)) {
+		old = pmdp_invalidate_ad(vma, addr, pmdp);
+		pmd = pmd_mkuffd_wp(old);
+		set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+	} else if (is_migration_entry(pmd_to_swp_entry(pmd))) {
+		pmd = pmd_swp_mkuffd_wp(pmd);
+		set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+	}
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+#ifdef CONFIG_HUGETLB_PAGE
+static unsigned long pagemap_hugetlb_category(pte_t pte)
+{
+	unsigned long categories = PAGE_IS_HUGE;
+
+	/*
+	 * According to pagemap_hugetlb_range(), file-backed HugeTLB
+	 * page cannot be swapped. So PAGE_IS_FILE is not checked for
+	 * swapped pages.
+	 */
+	if (pte_present(pte)) {
+		categories |= PAGE_IS_PRESENT;
+		if (!huge_pte_uffd_wp(pte))
+			categories |= PAGE_IS_WRITTEN;
+		if (!PageAnon(pte_page(pte)))
+			categories |= PAGE_IS_FILE;
+		if (is_zero_pfn(pte_pfn(pte)))
+			categories |= PAGE_IS_PFNZERO;
+	} else if (is_swap_pte(pte)) {
+		categories |= PAGE_IS_SWAPPED;
+		if (!pte_swp_uffd_wp_any(pte))
+			categories |= PAGE_IS_WRITTEN;
+	}
+
+	return categories;
+}
+
+static void make_uffd_wp_huge_pte(struct vm_area_struct *vma,
+				  unsigned long addr, pte_t *ptep,
+				  pte_t ptent)
+{
+	if (is_hugetlb_entry_hwpoisoned(ptent) || is_pte_marker(ptent))
+		return;
+
+	if (is_hugetlb_entry_migration(ptent))
+		set_huge_pte_at(vma->vm_mm, addr, ptep,
+				pte_swp_mkuffd_wp(ptent));
+	else if (!huge_pte_none(ptent))
+		huge_ptep_modify_prot_commit(vma, addr, ptep, ptent,
+					     huge_pte_mkuffd_wp(ptent));
+	else
+		set_huge_pte_at(vma->vm_mm, addr, ptep,
+				make_pte_marker(PTE_MARKER_UFFD_WP));
+}
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static bool pagemap_scan_is_interesting_page(unsigned long categories,
+					     const struct pagemap_scan_private *p)
+{
+	categories ^= p->arg.category_inverted;
+	if ((categories & p->arg.category_mask) != p->arg.category_mask)
+		return false;
+	if (p->arg.category_anyof_mask && !(categories & p->arg.category_anyof_mask))
+		return false;
+
+	return true;
+}
+
+static bool pagemap_scan_is_interesting_vma(unsigned long categories,
+					    const struct pagemap_scan_private *p)
+{
+	unsigned long required = p->arg.category_mask & PAGE_IS_WPALLOWED;
+
+	categories ^= p->arg.category_inverted;
+	if ((categories & required) != required)
+		return false;
+
+	return true;
+}
+
+static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
+				  struct mm_walk *walk)
+{
+	struct pagemap_scan_private *p = walk->private;
+	struct vm_area_struct *vma = walk->vma;
+	unsigned long vma_category = 0;
+
+	if (userfaultfd_wp_async(vma) && userfaultfd_wp_use_markers(vma))
+		vma_category |= PAGE_IS_WPALLOWED;
+	else if (p->arg.flags & PM_SCAN_CHECK_WPASYNC)
+		return -EPERM;
+
+	if (vma->vm_flags & VM_PFNMAP)
+		return 1;
+
+	if (!pagemap_scan_is_interesting_vma(vma_category, p))
+		return 1;
+
+	p->cur_vma_category = vma_category;
+
+	return 0;
+}
+
+static bool pagemap_scan_push_range(unsigned long categories,
+				    struct pagemap_scan_private *p,
+				    unsigned long addr, unsigned long end)
+{
+	struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index];
+
+	/*
+	 * When there is no output buffer provided at all, the sentinel values
+	 * won't match here. There is no other way for `cur_buf->end` to be
+	 * non-zero other than it being non-empty.
+	 */
+	if (addr == cur_buf->end && categories == cur_buf->categories) {
+		cur_buf->end = end;
+		return true;
+	}
+
+	if (cur_buf->end) {
+		if (p->vec_buf_index >= p->vec_buf_len - 1)
+			return false;
+
+		cur_buf = &p->vec_buf[++p->vec_buf_index];
+	}
+
+	cur_buf->start = addr;
+	cur_buf->end = end;
+	cur_buf->categories = categories;
+
+	return true;
+}
+
+static void pagemap_scan_backout_range(struct pagemap_scan_private *p,
+				       unsigned long addr, unsigned long end)
+{
+	struct page_region *cur_buf = &p->vec_buf[p->vec_buf_index];
+
+	if (cur_buf->start != addr)
+		cur_buf->end = addr;
+	else
+		cur_buf->start = cur_buf->end = 0;
+
+	p->found_pages -= (end - addr) / PAGE_SIZE;
+}
+
+static int pagemap_scan_output(unsigned long categories,
+			       struct pagemap_scan_private *p,
+			       unsigned long addr, unsigned long *end)
+{
+	unsigned long n_pages, total_pages;
+	int ret = 0;
+
+	if (!p->vec_buf)
+		return 0;
+
+	categories &= p->arg.return_mask;
+
+	n_pages = (*end - addr) / PAGE_SIZE;
+	if (check_add_overflow(p->found_pages, n_pages, &total_pages) ||
+	    total_pages > p->arg.max_pages) {
+		size_t n_too_much = total_pages - p->arg.max_pages;
+		*end -= n_too_much * PAGE_SIZE;
+		n_pages -= n_too_much;
+		ret = -ENOSPC;
+	}
+
+	if (!pagemap_scan_push_range(categories, p, addr, *end)) {
+		*end = addr;
+		n_pages = 0;
+		ret = -ENOSPC;
+	}
+
+	p->found_pages += n_pages;
+	if (ret)
+		p->arg.walk_end = *end;
+
+	return ret;
+}
+
+static int pagemap_scan_thp_entry(pmd_t *pmd, unsigned long start,
+				  unsigned long end, struct mm_walk *walk)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	struct pagemap_scan_private *p = walk->private;
+	struct vm_area_struct *vma = walk->vma;
+	unsigned long categories;
+	spinlock_t *ptl;
+	int ret = 0;
+
+	ptl = pmd_trans_huge_lock(pmd, vma);
+	if (!ptl)
+		return -ENOENT;
+
+	categories = p->cur_vma_category | pagemap_thp_category(*pmd);
+
+	if (!pagemap_scan_is_interesting_page(categories, p))
+		goto out_unlock;
+
+	ret = pagemap_scan_output(categories, p, start, &end);
+	if (start == end)
+		goto out_unlock;
+
+	if (~p->arg.flags & PM_SCAN_WP_MATCHING)
+		goto out_unlock;
+	if (~categories & PAGE_IS_WRITTEN)
+		goto out_unlock;
+
+	/*
+	 * Break huge page into small pages if the WP operation
+	 * needs to be performed on a portion of the huge page.
+	 */
+	if (end != start + HPAGE_SIZE) {
+		spin_unlock(ptl);
+		split_huge_pmd(vma, pmd, start);
+		pagemap_scan_backout_range(p, start, end);
+		/* Report as if there was no THP */
+		return -ENOENT;
+	}
+
+	make_uffd_wp_pmd(vma, start, pmd);
+	flush_tlb_range(vma, start, end);
+out_unlock:
+	spin_unlock(ptl);
+	return ret;
+#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
+	return -ENOENT;
+#endif
+}
+
+static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
+				  unsigned long end, struct mm_walk *walk)
+{
+	struct pagemap_scan_private *p = walk->private;
+	struct vm_area_struct *vma = walk->vma;
+	unsigned long addr, flush_end = 0;
+	pte_t *pte, *start_pte;
+	spinlock_t *ptl;
+	int ret;
+
+	arch_enter_lazy_mmu_mode();
+
+	ret = pagemap_scan_thp_entry(pmd, start, end, walk);
+	if (ret != -ENOENT) {
+		arch_leave_lazy_mmu_mode();
+		return ret;
+	}
+
+	ret = 0;
+	start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
+	if (!pte) {
+		arch_leave_lazy_mmu_mode();
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
+
+	for (addr = start; addr != end; pte++, addr += PAGE_SIZE) {
+		unsigned long categories = p->cur_vma_category |
+					   pagemap_page_category(p, vma, addr, ptep_get(pte));
+		unsigned long next = addr + PAGE_SIZE;
+
+		if (!pagemap_scan_is_interesting_page(categories, p))
+			continue;
+
+		ret = pagemap_scan_output(categories, p, addr, &next);
+		if (next == addr)
+			break;
+
+		if (~p->arg.flags & PM_SCAN_WP_MATCHING)
+			continue;
+		if (~categories & PAGE_IS_WRITTEN)
+			continue;
+
+		make_uffd_wp_pte(vma, addr, pte);
+		if (!flush_end)
+			start = addr;
+		flush_end = next;
+	}
+
+	if (flush_end)
+		flush_tlb_range(vma, start, addr);
+
+	pte_unmap_unlock(start_pte, ptl);
+	arch_leave_lazy_mmu_mode();
+
+	cond_resched();
+	return ret;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask,
+				      unsigned long start, unsigned long end,
+				      struct mm_walk *walk)
+{
+	struct pagemap_scan_private *p = walk->private;
+	struct vm_area_struct *vma = walk->vma;
+	unsigned long categories;
+	spinlock_t *ptl;
+	int ret = 0;
+	pte_t pte;
+
+	if (~p->arg.flags & PM_SCAN_WP_MATCHING) {
+		/* Go the short route when not write-protecting pages. */
+
+		pte = huge_ptep_get(ptep);
+		categories = p->cur_vma_category | pagemap_hugetlb_category(pte);
+
+		if (!pagemap_scan_is_interesting_page(categories, p))
+			return 0;
+
+		return pagemap_scan_output(categories, p, start, &end);
+	}
+
+	i_mmap_lock_write(vma->vm_file->f_mapping);
+	ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, ptep);
+
+	pte = huge_ptep_get(ptep);
+	categories = p->cur_vma_category | pagemap_hugetlb_category(pte);
+
+	if (!pagemap_scan_is_interesting_page(categories, p))
+		goto out_unlock;
+
+	ret = pagemap_scan_output(categories, p, start, &end);
+	if (start == end)
+		goto out_unlock;
+
+	if (~categories & PAGE_IS_WRITTEN)
+		goto out_unlock;
+
+	if (end != start + HPAGE_SIZE) {
+		/* Partial HugeTLB page WP isn't possible. */
+		pagemap_scan_backout_range(p, start, end);
+		p->arg.walk_end = start;
+		ret = 0;
+		goto out_unlock;
+	}
+
+	make_uffd_wp_huge_pte(vma, start, ptep, pte);
+	flush_hugetlb_tlb_range(vma, start, end);
+
+out_unlock:
+	spin_unlock(ptl);
+	i_mmap_unlock_write(vma->vm_file->f_mapping);
+
+	return ret;
+}
+#else
+#define pagemap_scan_hugetlb_entry NULL
+#endif
+
+static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
+				 int depth, struct mm_walk *walk)
+{
+	struct pagemap_scan_private *p = walk->private;
+	struct vm_area_struct *vma = walk->vma;
+	int ret, err;
+
+	if (!vma || !pagemap_scan_is_interesting_page(p->cur_vma_category, p))
+		return 0;
+
+	ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end);
+	if (addr == end)
+		return ret;
+
+	if (~p->arg.flags & PM_SCAN_WP_MATCHING)
+		return ret;
+
+	err = uffd_wp_range(vma, addr, end - addr, true);
+	if (err < 0)
+		ret = err;
+
+	return ret;
+}
+
+static const struct mm_walk_ops pagemap_scan_ops = {
+	.test_walk = pagemap_scan_test_walk,
+	.pmd_entry = pagemap_scan_pmd_entry,
+	.pte_hole = pagemap_scan_pte_hole,
+	.hugetlb_entry = pagemap_scan_hugetlb_entry,
+};
+
+static int pagemap_scan_get_args(struct pm_scan_arg *arg,
+				 unsigned long uarg)
+{
+	if (copy_from_user(arg, (void __user *)uarg, sizeof(*arg)))
+		return -EFAULT;
+
+	if (arg->size != sizeof(struct pm_scan_arg))
+		return -EINVAL;
+
+	/* Validate requested features */
+	if (arg->flags & ~PM_SCAN_FLAGS)
+		return -EINVAL;
+	if ((arg->category_inverted | arg->category_mask |
+	     arg->category_anyof_mask | arg->return_mask) & ~PM_SCAN_CATEGORIES)
+		return -EINVAL;
+
+	arg->start = untagged_addr((unsigned long)arg->start);
+	arg->end = untagged_addr((unsigned long)arg->end);
+	arg->vec = untagged_addr((unsigned long)arg->vec);
+
+	/* Validate memory pointers */
+	if (!IS_ALIGNED(arg->start, PAGE_SIZE))
+		return -EINVAL;
+	if (!access_ok((void __user *)(long)arg->start, arg->end - arg->start))
+		return -EFAULT;
+	if (!arg->vec && arg->vec_len)
+		return -EINVAL;
+	if (arg->vec && !access_ok((void __user *)(long)arg->vec,
+			      arg->vec_len * sizeof(struct page_region)))
+		return -EFAULT;
+
+	/* Fixup default values */
+	arg->end = ALIGN(arg->end, PAGE_SIZE);
+	arg->walk_end = 0;
+	if (!arg->max_pages)
+		arg->max_pages = ULONG_MAX;
+
+	return 0;
+}
+
+static int pagemap_scan_writeback_args(struct pm_scan_arg *arg,
+				       unsigned long uargl)
+{
+	struct pm_scan_arg __user *uarg	= (void __user *)uargl;
+
+	if (copy_to_user(&uarg->walk_end, &arg->walk_end, sizeof(arg->walk_end)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int pagemap_scan_init_bounce_buffer(struct pagemap_scan_private *p)
+{
+	if (!p->arg.vec_len)
+		return 0;
+
+	p->vec_buf_len = min_t(size_t, PAGEMAP_WALK_SIZE >> PAGE_SHIFT,
+			       p->arg.vec_len);
+	p->vec_buf = kmalloc_array(p->vec_buf_len, sizeof(*p->vec_buf),
+				   GFP_KERNEL);
+	if (!p->vec_buf)
+		return -ENOMEM;
+
+	p->vec_buf->start = p->vec_buf->end = 0;
+	p->vec_out = (struct page_region __user *)(long)p->arg.vec;
+
+	return 0;
+}
+
+static long pagemap_scan_flush_buffer(struct pagemap_scan_private *p)
+{
+	const struct page_region *buf = p->vec_buf;
+	long n = p->vec_buf_index;
+
+	if (!p->vec_buf)
+		return 0;
+
+	if (buf[n].end != buf[n].start)
+		n++;
+
+	if (!n)
+		return 0;
+
+	if (copy_to_user(p->vec_out, buf, n * sizeof(*buf)))
+		return -EFAULT;
+
+	p->arg.vec_len -= n;
+	p->vec_out += n;
+
+	p->vec_buf_index = 0;
+	p->vec_buf_len = min_t(size_t, p->vec_buf_len, p->arg.vec_len);
+	p->vec_buf->start = p->vec_buf->end = 0;
+
+	return n;
+}
+
+static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg)
+{
+	struct mmu_notifier_range range;
+	struct pagemap_scan_private p = {0};
+	unsigned long walk_start;
+	size_t n_ranges_out = 0;
+	int ret;
+
+	ret = pagemap_scan_get_args(&p.arg, uarg);
+	if (ret)
+		return ret;
+
+	p.masks_of_interest = p.arg.category_mask | p.arg.category_anyof_mask |
+			      p.arg.return_mask;
+	ret = pagemap_scan_init_bounce_buffer(&p);
+	if (ret)
+		return ret;
+
+	/* Protection change for the range is going to happen. */
+	if (p.arg.flags & PM_SCAN_WP_MATCHING) {
+		mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
+					mm, p.arg.start, p.arg.end);
+		mmu_notifier_invalidate_range_start(&range);
+	}
+
+	for (walk_start = p.arg.start; walk_start < p.arg.end;
+			walk_start = p.arg.walk_end) {
+		long n_out;
+
+		if (fatal_signal_pending(current)) {
+			ret = -EINTR;
+			break;
+		}
+
+		ret = mmap_read_lock_killable(mm);
+		if (ret)
+			break;
+		ret = walk_page_range(mm, walk_start, p.arg.end,
+				      &pagemap_scan_ops, &p);
+		mmap_read_unlock(mm);
+
+		n_out = pagemap_scan_flush_buffer(&p);
+		if (n_out < 0)
+			ret = n_out;
+		else
+			n_ranges_out += n_out;
+
+		if (ret != -ENOSPC)
+			break;
+
+		if (p.arg.vec_len == 0 || p.found_pages == p.arg.max_pages)
+			break;
+	}
+
+	/* ENOSPC signifies early stop (buffer full) from the walk. */
+	if (!ret || ret == -ENOSPC)
+		ret = n_ranges_out;
+
+	/* The walk_end isn't set when ret is zero */
+	if (!p.arg.walk_end)
+		p.arg.walk_end = p.arg.end;
+	if (pagemap_scan_writeback_args(&p.arg, uarg))
+		ret = -EFAULT;
+
+	if (p.arg.flags & PM_SCAN_WP_MATCHING)
+		mmu_notifier_invalidate_range_end(&range);
+
+	kfree(p.vec_buf);
+	return ret;
+}
+
+static long do_pagemap_cmd(struct file *file, unsigned int cmd,
+			   unsigned long arg)
+{
+	struct mm_struct *mm = file->private_data;
+
+	switch (cmd) {
+	case PAGEMAP_SCAN:
+		return do_pagemap_scan(mm, arg);
+
+	default:
+		return -EINVAL;
+	}
+}
+
 const struct file_operations proc_pagemap_operations = {
 	.llseek		= mem_lseek, /* borrow this */
 	.read		= pagemap_read,
 	.open		= pagemap_open,
 	.release	= pagemap_release,
+	.unlocked_ioctl = do_pagemap_cmd,
+	.compat_ioctl	= do_pagemap_cmd,
 };
 #endif /* CONFIG_PROC_PAGE_MONITOR */
 
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 0a393bc02f25b..8f8ff07453f22 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -259,6 +259,7 @@  long hugetlb_change_protection(struct vm_area_struct *vma,
 		unsigned long cp_flags);
 
 bool is_hugetlb_entry_migration(pte_t pte);
+bool is_hugetlb_entry_hwpoisoned(pte_t pte);
 void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
 
 #else /* !CONFIG_HUGETLB_PAGE */
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index c98df391bfd8f..f2dc19f40d059 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -221,6 +221,13 @@  static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
 	return VM_FAULT_SIGBUS;
 }
 
+static inline long uffd_wp_range(struct vm_area_struct *vma,
+				 unsigned long start, unsigned long len,
+				 bool enable_wp)
+{
+	return false;
+}
+
 static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
 					struct vm_userfaultfd_ctx vm_ctx)
 {
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index b7b56871029c5..da43810b74856 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -305,4 +305,63 @@  typedef int __bitwise __kernel_rwf_t;
 #define RWF_SUPPORTED	(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\
 			 RWF_APPEND)
 
+/* Pagemap ioctl */
+#define PAGEMAP_SCAN	_IOWR('f', 16, struct pm_scan_arg)
+
+/* Bitmasks provided in pm_scan_args masks and reported in page_region.categories. */
+#define PAGE_IS_WPALLOWED	(1 << 0)
+#define PAGE_IS_WRITTEN		(1 << 1)
+#define PAGE_IS_FILE		(1 << 2)
+#define PAGE_IS_PRESENT		(1 << 3)
+#define PAGE_IS_SWAPPED		(1 << 4)
+#define PAGE_IS_PFNZERO		(1 << 5)
+#define PAGE_IS_HUGE		(1 << 6)
+
+/*
+ * struct page_region - Page region with flags
+ * @start:	Start of the region
+ * @end:	End of the region (exclusive)
+ * @categories:	PAGE_IS_* category bitmask for the region
+ */
+struct page_region {
+	__u64 start;
+	__u64 end;
+	__u64 categories;
+};
+
+/* Flags for PAGEMAP_SCAN ioctl */
+#define PM_SCAN_WP_MATCHING	(1 << 0)	/* Write protect the pages matched. */
+#define PM_SCAN_CHECK_WPASYNC	(1 << 1)	/* Abort the scan when a non-WP-enabled page is found. */
+
+/*
+ * struct pm_scan_arg - Pagemap ioctl argument
+ * @size:		Size of the structure
+ * @flags:		Flags for the IOCTL
+ * @start:		Starting address of the region
+ * @end:		Ending address of the region
+ * @walk_end		Address where the scan stopped (written by kernel).
+ *			walk_end == end (address tags cleared) informs that the scan completed on entire range.
+ * @vec:		Address of page_region struct array for output
+ * @vec_len:		Length of the page_region struct array
+ * @max_pages:		Optional limit for number of returned pages (0 = disabled)
+ * @category_inverted:	PAGE_IS_* categories which values match if 0 instead of 1
+ * @category_mask:	Skip pages for which any category doesn't match
+ * @category_anyof_mask: Skip pages for which no category matches
+ * @return_mask:	PAGE_IS_* categories that are to be reported in `page_region`s returned
+ */
+struct pm_scan_arg {
+	__u64 size;
+	__u64 flags;
+	__u64 start;
+	__u64 end;
+	__u64 walk_end;
+	__u64 vec;
+	__u64 vec_len;
+	__u64 max_pages;
+	__u64 category_inverted;
+	__u64 category_mask;
+	__u64 category_anyof_mask;
+	__u64 return_mask;
+};
+
 #endif /* _UAPI_LINUX_FS_H */
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7ed95353c46a7..a24eb6352d6a5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5008,7 +5008,7 @@  bool is_hugetlb_entry_migration(pte_t pte)
 		return false;
 }
 
-static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
+bool is_hugetlb_entry_hwpoisoned(pte_t pte)
 {
 	swp_entry_t swp;