Merge branch 'akpm' (patches from Andrew)

[linux-2.6-microblaze.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 7d60876..feff48e 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2892,11 +2892,13 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
                entry = mk_pte(new_page, vma->vm_page_prot);
                entry = pte_sw_mkyoung(entry);
                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+
                /*
                 * Clear the pte entry and flush it first, before updating the
-                * pte with the new entry. This will avoid a race condition
-                * seen in the presence of one thread doing SMC and another
-                * thread doing COW.
+                * pte with the new entry, to keep TLBs on different CPUs in
+                * sync. This code used to set the new PTE then flush TLBs, but
+                * that left a window where the new PTE could be loaded into
+                * some TLBs while the old PTE remains in others.
                 */
                ptep_clear_flush_notify(vma, vmf->address, vmf->pte);
                page_add_new_anon_rmap(new_page, vma, vmf->address, false);