patches/old/mm-rmap-add-helper-to-restart-pgtable-walk-on-changes.patch

From: Lance Yang <ioworker0@gmail.com>
Subject: mm/rmap: add helper to restart pgtable walk on changes
Date: Mon, 10 Jun 2024 20:02:07 +0800

Introduce the page_vma_mapped_walk_restart() helper to handle scenarios
where the page table walk needs to be restarted due to changes in the page
table, such as when a PMD is split.  It releases the PTL held during the
previous walk and resets the state, allowing a new walk to start at the
current address stored in pvmw->address.

Link: https://lkml.kernel.org/r/20240610120209.66311-3-ioworker0@gmail.com
Signed-off-by: Lance Yang <ioworker0@gmail.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Cc: Bang Li <libang.li@antgroup.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Fangrui Song <maskray@google.com>
Cc: Jeff Xie <xiehuan09@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/rmap.h |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

--- a/include/linux/rmap.h~mm-rmap-add-helper-to-restart-pgtable-walk-on-changes
+++ a/include/linux/rmap.h
@@ -703,6 +703,28 @@ static inline void page_vma_mapped_walk_
 		spin_unlock(pvmw->ptl);
 }
 
+/**
+ * page_vma_mapped_walk_restart - Restart the page table walk.
+ * @pvmw: Pointer to struct page_vma_mapped_walk.
+ *
+ * It restarts the page table walk when changes occur in the page
+ * table, such as splitting a PMD. Ensures that the PTL held during
+ * the previous walk is released and resets the state to allow for
+ * a new walk starting at the current address stored in pvmw->address.
+ */
+static inline void
+page_vma_mapped_walk_restart(struct page_vma_mapped_walk *pvmw)
+{
+	WARN_ON_ONCE(!pvmw->pmd);
+	WARN_ON_ONCE(!pvmw->ptl);
+
+	if (pvmw->ptl)
+		spin_unlock(pvmw->ptl);
+
+	pvmw->ptl = NULL;
+	pvmw->pmd = NULL;
+}
+
 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
 
 /*
_