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fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs
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. [[email protected]: update it for "mm: hugetlb: add huge page size param to set_huge_pte_at()"] [[email protected]: fix CONFIG_HUGETLB_PAGE=n warning] [[email protected]: hide unused pagemap_scan_backout_range() function] Link: https://lkml.kernel.org/r/[email protected] [[email protected]: fix "fs/proc/task_mmu: hide unused pagemap_scan_backout_range() function"] Link: https://lkml.kernel.org/r/[email protected] Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Muhammad Usama Anjum <[email protected]> Signed-off-by: Michał Mirosław <[email protected]> Signed-off-by: Arnd Bergmann <[email protected]> Signed-off-by: Stephen Rothwell <[email protected]> Reviewed-by: Andrei Vagin <[email protected]> Reviewed-by: Michał Mirosław <[email protected]> Cc: Alex Sierra <[email protected]> Cc: Al Viro <[email protected]> Cc: Axel Rasmussen <[email protected]> Cc: Christian Brauner <[email protected]> Cc: Cyrill Gorcunov <[email protected]> Cc: Dan Williams <[email protected]> Cc: David Hildenbrand <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Gustavo A. R. Silva <[email protected]> Cc: "Liam R. Howlett" <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: Michal Miroslaw <[email protected]> Cc: Mike Rapoport (IBM) <[email protected]> Cc: Nadav Amit <[email protected]> Cc: Pasha Tatashin <[email protected]> Cc: Paul Gofman <[email protected]> Cc: Peter Xu <[email protected]> Cc: Shuah Khan <[email protected]> Cc: Suren Baghdasaryan <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Yang Shi <[email protected]> Cc: Yun Zhou <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
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