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-rw-r--r--mm/mempolicy.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index e93cc740c22..4f71cfd29c6 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -422,6 +422,37 @@ static int contextualize_policy(int mode, nodemask_t *nodes)
return mpol_check_policy(mode, nodes);
}
+
+/*
+ * Update task->flags PF_MEMPOLICY bit: set iff non-default
+ * mempolicy. Allows more rapid checking of this (combined perhaps
+ * with other PF_* flag bits) on memory allocation hot code paths.
+ *
+ * If called from outside this file, the task 'p' should -only- be
+ * a newly forked child not yet visible on the task list, because
+ * manipulating the task flags of a visible task is not safe.
+ *
+ * The above limitation is why this routine has the funny name
+ * mpol_fix_fork_child_flag().
+ *
+ * It is also safe to call this with a task pointer of current,
+ * which the static wrapper mpol_set_task_struct_flag() does,
+ * for use within this file.
+ */
+
+void mpol_fix_fork_child_flag(struct task_struct *p)
+{
+ if (p->mempolicy)
+ p->flags |= PF_MEMPOLICY;
+ else
+ p->flags &= ~PF_MEMPOLICY;
+}
+
+static void mpol_set_task_struct_flag(void)
+{
+ mpol_fix_fork_child_flag(current);
+}
+
/* Set the process memory policy */
long do_set_mempolicy(int mode, nodemask_t *nodes)
{
@@ -434,6 +465,7 @@ long do_set_mempolicy(int mode, nodemask_t *nodes)
return PTR_ERR(new);
mpol_free(current->mempolicy);
current->mempolicy = new;
+ mpol_set_task_struct_flag();
if (new && new->policy == MPOL_INTERLEAVE)
current->il_next = first_node(new->v.nodes);
return 0;