On 10.06.24 14:02, Lance Yang wrote:
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.
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
---
include/linux/rmap.h | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 7229b9baf20d..5f18509610cc 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -710,6 +710,28 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
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);
Can we have this more general, like
WARN_ON_ONCE(!pvmw->pmd && !pvmw->pte);
And then setting both to NULL below?
+ WARN_ON_ONCE(!pvmw->ptl);
This is confusing: you check for ptl below. What would be clearer is
if (likely(pvmw->ptl))
spin_unlock(pvmw->ptl);
else
WARN_ON_ONCE(1);
+
+ if (pvmw->ptl)
+ spin_unlock(pvmw->ptl);
+
+ pvmw->ptl = NULL;
+ pvmw->pmd = NULL;
+}
+
bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
/*
I'd suggest squashing that into the next patch.
--
Cheers,
David / dhildenb
