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-rw-r--r--mm/mempolicy.c124
1 files changed, 105 insertions, 19 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 0c73c8b814c..8a993db8802 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -119,7 +119,22 @@ struct mempolicy default_policy = {
static const struct mempolicy_operations {
int (*create)(struct mempolicy *pol, const nodemask_t *nodes);
- void (*rebind)(struct mempolicy *pol, const nodemask_t *nodes);
+ /*
+ * If read-side task has no lock to protect task->mempolicy, write-side
+ * task will rebind the task->mempolicy by two step. The first step is
+ * setting all the newly nodes, and the second step is cleaning all the
+ * disallowed nodes. In this way, we can avoid finding no node to alloc
+ * page.
+ * If we have a lock to protect task->mempolicy in read-side, we do
+ * rebind directly.
+ *
+ * step:
+ * MPOL_REBIND_ONCE - do rebind work at once
+ * MPOL_REBIND_STEP1 - set all the newly nodes
+ * MPOL_REBIND_STEP2 - clean all the disallowed nodes
+ */
+ void (*rebind)(struct mempolicy *pol, const nodemask_t *nodes,
+ enum mpol_rebind_step step);
} mpol_ops[MPOL_MAX];
/* Check that the nodemask contains at least one populated zone */
@@ -274,12 +289,19 @@ void __mpol_put(struct mempolicy *p)
kmem_cache_free(policy_cache, p);
}
-static void mpol_rebind_default(struct mempolicy *pol, const nodemask_t *nodes)
+static void mpol_rebind_default(struct mempolicy *pol, const nodemask_t *nodes,
+ enum mpol_rebind_step step)
{
}
-static void mpol_rebind_nodemask(struct mempolicy *pol,
- const nodemask_t *nodes)
+/*
+ * step:
+ * MPOL_REBIND_ONCE - do rebind work at once
+ * MPOL_REBIND_STEP1 - set all the newly nodes
+ * MPOL_REBIND_STEP2 - clean all the disallowed nodes
+ */
+static void mpol_rebind_nodemask(struct mempolicy *pol, const nodemask_t *nodes,
+ enum mpol_rebind_step step)
{
nodemask_t tmp;
@@ -288,12 +310,31 @@ static void mpol_rebind_nodemask(struct mempolicy *pol,
else if (pol->flags & MPOL_F_RELATIVE_NODES)
mpol_relative_nodemask(&tmp, &pol->w.user_nodemask, nodes);
else {
- nodes_remap(tmp, pol->v.nodes, pol->w.cpuset_mems_allowed,
- *nodes);
- pol->w.cpuset_mems_allowed = *nodes;
+ /*
+ * if step == 1, we use ->w.cpuset_mems_allowed to cache the
+ * result
+ */
+ if (step == MPOL_REBIND_ONCE || step == MPOL_REBIND_STEP1) {
+ nodes_remap(tmp, pol->v.nodes,
+ pol->w.cpuset_mems_allowed, *nodes);
+ pol->w.cpuset_mems_allowed = step ? tmp : *nodes;
+ } else if (step == MPOL_REBIND_STEP2) {
+ tmp = pol->w.cpuset_mems_allowed;
+ pol->w.cpuset_mems_allowed = *nodes;
+ } else
+ BUG();
}
- pol->v.nodes = tmp;
+ if (nodes_empty(tmp))
+ tmp = *nodes;
+
+ if (step == MPOL_REBIND_STEP1)
+ nodes_or(pol->v.nodes, pol->v.nodes, tmp);
+ else if (step == MPOL_REBIND_ONCE || step == MPOL_REBIND_STEP2)
+ pol->v.nodes = tmp;
+ else
+ BUG();
+
if (!node_isset(current->il_next, tmp)) {
current->il_next = next_node(current->il_next, tmp);
if (current->il_next >= MAX_NUMNODES)
@@ -304,7 +345,8 @@ static void mpol_rebind_nodemask(struct mempolicy *pol,
}
static void mpol_rebind_preferred(struct mempolicy *pol,
- const nodemask_t *nodes)
+ const nodemask_t *nodes,
+ enum mpol_rebind_step step)
{
nodemask_t tmp;
@@ -327,16 +369,45 @@ static void mpol_rebind_preferred(struct mempolicy *pol,
}
}
-/* Migrate a policy to a different set of nodes */
-static void mpol_rebind_policy(struct mempolicy *pol,
- const nodemask_t *newmask)
+/*
+ * mpol_rebind_policy - Migrate a policy to a different set of nodes
+ *
+ * If read-side task has no lock to protect task->mempolicy, write-side
+ * task will rebind the task->mempolicy by two step. The first step is
+ * setting all the newly nodes, and the second step is cleaning all the
+ * disallowed nodes. In this way, we can avoid finding no node to alloc
+ * page.
+ * If we have a lock to protect task->mempolicy in read-side, we do
+ * rebind directly.
+ *
+ * step:
+ * MPOL_REBIND_ONCE - do rebind work at once
+ * MPOL_REBIND_STEP1 - set all the newly nodes
+ * MPOL_REBIND_STEP2 - clean all the disallowed nodes
+ */
+static void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask,
+ enum mpol_rebind_step step)
{
if (!pol)
return;
- if (!mpol_store_user_nodemask(pol) &&
+ if (!mpol_store_user_nodemask(pol) && step == 0 &&
nodes_equal(pol->w.cpuset_mems_allowed, *newmask))
return;
- mpol_ops[pol->mode].rebind(pol, newmask);
+
+ if (step == MPOL_REBIND_STEP1 && (pol->flags & MPOL_F_REBINDING))
+ return;
+
+ if (step == MPOL_REBIND_STEP2 && !(pol->flags & MPOL_F_REBINDING))
+ BUG();
+
+ if (step == MPOL_REBIND_STEP1)
+ pol->flags |= MPOL_F_REBINDING;
+ else if (step == MPOL_REBIND_STEP2)
+ pol->flags &= ~MPOL_F_REBINDING;
+ else if (step >= MPOL_REBIND_NSTEP)
+ BUG();
+
+ mpol_ops[pol->mode].rebind(pol, newmask, step);
}
/*
@@ -346,9 +417,10 @@ static void mpol_rebind_policy(struct mempolicy *pol,
* Called with task's alloc_lock held.
*/
-void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new)
+void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new,
+ enum mpol_rebind_step step)
{
- mpol_rebind_policy(tsk->mempolicy, new);
+ mpol_rebind_policy(tsk->mempolicy, new, step);
}
/*
@@ -363,7 +435,7 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
down_write(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next)
- mpol_rebind_policy(vma->vm_policy, new);
+ mpol_rebind_policy(vma->vm_policy, new, MPOL_REBIND_ONCE);
up_write(&mm->mmap_sem);
}
@@ -1745,6 +1817,9 @@ EXPORT_SYMBOL(alloc_pages_current);
* with the mems_allowed returned by cpuset_mems_allowed(). This
* keeps mempolicies cpuset relative after its cpuset moves. See
* further kernel/cpuset.c update_nodemask().
+ *
+ * current's mempolicy may be rebinded by the other task(the task that changes
+ * cpuset's mems), so we needn't do rebind work for current task.
*/
/* Slow path of a mempolicy duplicate */
@@ -1754,13 +1829,24 @@ struct mempolicy *__mpol_dup(struct mempolicy *old)
if (!new)
return ERR_PTR(-ENOMEM);
+
+ /* task's mempolicy is protected by alloc_lock */
+ if (old == current->mempolicy) {
+ task_lock(current);
+ *new = *old;
+ task_unlock(current);
+ } else
+ *new = *old;
+
rcu_read_lock();
if (current_cpuset_is_being_rebound()) {
nodemask_t mems = cpuset_mems_allowed(current);
- mpol_rebind_policy(old, &mems);
+ if (new->flags & MPOL_F_REBINDING)
+ mpol_rebind_policy(new, &mems, MPOL_REBIND_STEP2);
+ else
+ mpol_rebind_policy(new, &mems, MPOL_REBIND_ONCE);
}
rcu_read_unlock();
- *new = *old;
atomic_set(&new->refcnt, 1);
return new;
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-12-14 17:09:32 +0000