diff options
| author | Andrei Vagin <avagin@gmail.com> | 2025-03-24 06:53:26 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-05-11 17:48:16 -0700 |
| commit | a516403787e08119b70ce8bfff985272ef318a58 (patch) | |
| tree | 5b41ff2b433823e4b4e5a4c2522a1f4479eda532 | |
| parent | 7eeafde0ac05fa84a74d37af0efe5c6c5270bbef (diff) | |
fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions
Patch series "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard
regions", v2.
Introduce the PAGE_IS_GUARD flag in the PAGEMAP_SCAN ioctl to expose
information about guard regions. This allows userspace tools, such as
CRIU, to detect and handle guard regions.
Currently, CRIU utilizes PAGEMAP_SCAN as a more efficient alternative to
parsing /proc/pid/pagemap. Without this change, guard regions are
incorrectly reported as swap-anon regions, leading CRIU to attempt dumping
them and subsequently failing.
The series includes updates to the documentation and selftests to reflect
the new functionality.
This patch (of 3):
Introduce the PAGE_IS_GUARD flag in the PAGEMAP_SCAN ioctl to expose
information about guard regions. This allows userspace tools, such as
CRIU, to detect and handle guard regions.
Link: https://lkml.kernel.org/r/20250324065328.107678-1-avagin@google.com
Link: https://lkml.kernel.org/r/20250324065328.107678-2-avagin@google.com
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | Documentation/admin-guide/mm/pagemap.rst | 1 | ||||
| -rw-r--r-- | fs/proc/task_mmu.c | 17 | ||||
| -rw-r--r-- | include/uapi/linux/fs.h | 1 |
3 files changed, 12 insertions, 7 deletions
diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst index afce291649dd..e60e9211fd9b 100644 --- a/Documentation/admin-guide/mm/pagemap.rst +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -250,6 +250,7 @@ Following flags about pages are currently supported: - ``PAGE_IS_PFNZERO`` - Page has zero PFN - ``PAGE_IS_HUGE`` - Page is PMD-mapped THP or Hugetlb backed - ``PAGE_IS_SOFT_DIRTY`` - Page is soft-dirty +- ``PAGE_IS_GUARD`` - Page is a part of a guard region 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 994cde10e3f4..b9e4fbbdf6e6 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -2087,7 +2087,8 @@ 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_SOFT_DIRTY) + PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY | \ + PAGE_IS_GUARD) #define PM_SCAN_FLAGS (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC) struct pagemap_scan_private { @@ -2128,12 +2129,14 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p, 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) && - !folio_test_anon(pfn_swap_entry_folio(swp))) - categories |= PAGE_IS_FILE; - } + swp = pte_to_swp_entry(pte); + if (is_guard_swp_entry(swp)) + categories |= PAGE_IS_GUARD; + else if ((p->masks_of_interest & PAGE_IS_FILE) && + is_pfn_swap_entry(swp) && + !folio_test_anon(pfn_swap_entry_folio(swp))) + categories |= PAGE_IS_FILE; + if (pte_swp_soft_dirty(pte)) categories |= PAGE_IS_SOFT_DIRTY; } diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index e762e1af650c..0098b0ce8ccb 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -361,6 +361,7 @@ typedef int __bitwise __kernel_rwf_t; #define PAGE_IS_PFNZERO (1 << 5) #define PAGE_IS_HUGE (1 << 6) #define PAGE_IS_SOFT_DIRTY (1 << 7) +#define PAGE_IS_GUARD (1 << 8) /* * struct page_region - Page region with flags |