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

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