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-rw-r--r--mm/memory.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c
index b8f97b8575b7..15e1f19a3b10 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1310,6 +1310,28 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
*/
mark_page_accessed(page);
}
+ if (flags & FOLL_MLOCK) {
+ /*
+ * The preliminary mapping check is mainly to avoid the
+ * pointless overhead of lock_page on the ZERO_PAGE
+ * which might bounce very badly if there is contention.
+ *
+ * If the page is already locked, we don't need to
+ * handle it now - vmscan will handle it later if and
+ * when it attempts to reclaim the page.
+ */
+ if (page->mapping && trylock_page(page)) {
+ lru_add_drain(); /* push cached pages to LRU */
+ /*
+ * Because we lock page here and migration is
+ * blocked by the pte's page reference, we need
+ * only check for file-cache page truncation.
+ */
+ if (page->mapping)
+ mlock_vma_page(page);
+ unlock_page(page);
+ }
+ }
unlock:
pte_unmap_unlock(ptep, ptl);
out: