From e6a9a2cbc13bf43e4c03f57666e93d511249d5d7 Mon Sep 17 00:00:00 2001 From: Andrei Vagin Date: Mon, 6 Nov 2023 14:09:58 -0800 Subject: fs/proc/task_mmu: report SOFT_DIRTY bits through the PAGEMAP_SCAN ioctl MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. [avagin@google.com: update tools/include/uapi/linux/fs.h] Link: https://lkml.kernel.org/r/20231107164139.576046-1-avagin@google.com Link: https://lkml.kernel.org/r/20231106220959.296568-1-avagin@google.com Signed-off-by: Andrei Vagin Reviewed-by: Muhammad Usama Anjum Cc: Michał Mirosław Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/pagemap.rst | 1 + 1 file changed, 1 insertion(+) (limited to 'Documentation/admin-guide') 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. -- cgit v1.2.3