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Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c181
1 files changed, 91 insertions, 90 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7acf43bf04a2..08adaaae6fcc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2337,7 +2337,6 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
again:
if (*ptr) { /* css should be a valid one */
memcg = *ptr;
- VM_BUG_ON(css_is_removed(&memcg->css));
if (mem_cgroup_is_root(memcg))
goto done;
if (nr_pages == 1 && consume_stock(memcg))
@@ -2477,9 +2476,9 @@ static void __mem_cgroup_cancel_local_charge(struct mem_cgroup *memcg,
/*
* A helper function to get mem_cgroup from ID. must be called under
- * rcu_read_lock(). The caller must check css_is_removed() or some if
- * it's concern. (dropping refcnt from swap can be called against removed
- * memcg.)
+ * rcu_read_lock(). The caller is responsible for calling css_tryget if
+ * the mem_cgroup is used for charging. (dropping refcnt from swap can be
+ * called against removed memcg.)
*/
static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
{
@@ -2676,13 +2675,6 @@ static int mem_cgroup_move_account(struct page *page,
/* caller should have done css_get */
pc->mem_cgroup = to;
mem_cgroup_charge_statistics(to, anon, nr_pages);
- /*
- * We charges against "to" which may not have any tasks. Then, "to"
- * can be under rmdir(). But in current implementation, caller of
- * this function is just force_empty() and move charge, so it's
- * guaranteed that "to" is never removed. So, we don't check rmdir
- * status here.
- */
move_unlock_mem_cgroup(from, &flags);
ret = 0;
unlock:
@@ -2696,10 +2688,27 @@ out:
return ret;
}
-/*
- * move charges to its parent.
+/**
+ * mem_cgroup_move_parent - moves page to the parent group
+ * @page: the page to move
+ * @pc: page_cgroup of the page
+ * @child: page's cgroup
+ *
+ * move charges to its parent or the root cgroup if the group has no
+ * parent (aka use_hierarchy==0).
+ * Although this might fail (get_page_unless_zero, isolate_lru_page or
+ * mem_cgroup_move_account fails) the failure is always temporary and
+ * it signals a race with a page removal/uncharge or migration. In the
+ * first case the page is on the way out and it will vanish from the LRU
+ * on the next attempt and the call should be retried later.
+ * Isolation from the LRU fails only if page has been isolated from
+ * the LRU since we looked at it and that usually means either global
+ * reclaim or migration going on. The page will either get back to the
+ * LRU or vanish.
+ * Finaly mem_cgroup_move_account fails only if the page got uncharged
+ * (!PageCgroupUsed) or moved to a different group. The page will
+ * disappear in the next attempt.
*/
-
static int mem_cgroup_move_parent(struct page *page,
struct page_cgroup *pc,
struct mem_cgroup *child)
@@ -2709,9 +2718,7 @@ static int mem_cgroup_move_parent(struct page *page,
unsigned long uninitialized_var(flags);
int ret;
- /* Is ROOT ? */
- if (mem_cgroup_is_root(child))
- return -EINVAL;
+ VM_BUG_ON(mem_cgroup_is_root(child));
ret = -EBUSY;
if (!get_page_unless_zero(page))
@@ -2728,8 +2735,10 @@ static int mem_cgroup_move_parent(struct page *page,
if (!parent)
parent = root_mem_cgroup;
- if (nr_pages > 1)
+ if (nr_pages > 1) {
+ VM_BUG_ON(!PageTransHuge(page));
flags = compound_lock_irqsave(page);
+ }
ret = mem_cgroup_move_account(page, nr_pages,
pc, child, parent);
@@ -2871,7 +2880,6 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
return;
if (!memcg)
return;
- cgroup_exclude_rmdir(&memcg->css);
__mem_cgroup_commit_charge(memcg, page, 1, ctype, true);
/*
@@ -2885,12 +2893,6 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
swp_entry_t ent = {.val = page_private(page)};
mem_cgroup_uncharge_swap(ent);
}
- /*
- * At swapin, we may charge account against cgroup which has no tasks.
- * So, rmdir()->pre_destroy() can be called while we do this charge.
- * In that case, we need to call pre_destroy() again. check it here.
- */
- cgroup_release_and_wakeup_rmdir(&memcg->css);
}
void mem_cgroup_commit_charge_swapin(struct page *page,
@@ -3338,8 +3340,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg,
if (!memcg)
return;
- /* blocks rmdir() */
- cgroup_exclude_rmdir(&memcg->css);
+
if (!migration_ok) {
used = oldpage;
unused = newpage;
@@ -3373,13 +3374,6 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg,
*/
if (anon)
mem_cgroup_uncharge_page(used);
- /*
- * At migration, we may charge account against cgroup which has no
- * tasks.
- * So, rmdir()->pre_destroy() can be called while we do this charge.
- * In that case, we need to call pre_destroy() again. check it here.
- */
- cgroup_release_and_wakeup_rmdir(&memcg->css);
}
/*
@@ -3679,17 +3673,22 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
return nr_reclaimed;
}
-/*
+/**
+ * mem_cgroup_force_empty_list - clears LRU of a group
+ * @memcg: group to clear
+ * @node: NUMA node
+ * @zid: zone id
+ * @lru: lru to to clear
+ *
* Traverse a specified page_cgroup list and try to drop them all. This doesn't
- * reclaim the pages page themselves - it just removes the page_cgroups.
- * Returns true if some page_cgroups were not freed, indicating that the caller
- * must retry this operation.
+ * reclaim the pages page themselves - pages are moved to the parent (or root)
+ * group.
*/
-static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
+static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
int node, int zid, enum lru_list lru)
{
struct mem_cgroup_per_zone *mz;
- unsigned long flags, loop;
+ unsigned long flags;
struct list_head *list;
struct page *busy;
struct zone *zone;
@@ -3698,11 +3697,8 @@ static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
mz = mem_cgroup_zoneinfo(memcg, node, zid);
list = &mz->lruvec.lists[lru];
- loop = mz->lru_size[lru];
- /* give some margin against EBUSY etc...*/
- loop += 256;
busy = NULL;
- while (loop--) {
+ do {
struct page_cgroup *pc;
struct page *page;
@@ -3728,76 +3724,72 @@ static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
cond_resched();
} else
busy = NULL;
- }
- return !list_empty(list);
+ } while (!list_empty(list));
}
/*
- * make mem_cgroup's charge to be 0 if there is no task.
+ * make mem_cgroup's charge to be 0 if there is no task by moving
+ * all the charges and pages to the parent.
* This enables deleting this mem_cgroup.
+ *
+ * Caller is responsible for holding css reference on the memcg.
*/
-static int mem_cgroup_force_empty(struct mem_cgroup *memcg, bool free_all)
+static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
{
- int ret;
- int node, zid, shrink;
- int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
- struct cgroup *cgrp = memcg->css.cgroup;
-
- css_get(&memcg->css);
+ int node, zid;
- shrink = 0;
- /* should free all ? */
- if (free_all)
- goto try_to_free;
-move_account:
do {
- ret = -EBUSY;
- if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
- goto out;
/* This is for making all *used* pages to be on LRU. */
lru_add_drain_all();
drain_all_stock_sync(memcg);
- ret = 0;
mem_cgroup_start_move(memcg);
for_each_node_state(node, N_HIGH_MEMORY) {
- for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
+ for (zid = 0; zid < MAX_NR_ZONES; zid++) {
enum lru_list lru;
for_each_lru(lru) {
- ret = mem_cgroup_force_empty_list(memcg,
+ mem_cgroup_force_empty_list(memcg,
node, zid, lru);
- if (ret)
- break;
}
}
- if (ret)
- break;
}
mem_cgroup_end_move(memcg);
memcg_oom_recover(memcg);
cond_resched();
- /* "ret" should also be checked to ensure all lists are empty. */
- } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0 || ret);
-out:
- css_put(&memcg->css);
- return ret;
-try_to_free:
+ /*
+ * This is a safety check because mem_cgroup_force_empty_list
+ * could have raced with mem_cgroup_replace_page_cache callers
+ * so the lru seemed empty but the page could have been added
+ * right after the check. RES_USAGE should be safe as we always
+ * charge before adding to the LRU.
+ */
+ } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0);
+}
+
+/*
+ * Reclaims as many pages from the given memcg as possible and moves
+ * the rest to the parent.
+ *
+ * Caller is responsible for holding css reference for memcg.
+ */
+static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
+{
+ int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ struct cgroup *cgrp = memcg->css.cgroup;
+
/* returns EBUSY if there is a task or if we come here twice. */
- if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children) || shrink) {
- ret = -EBUSY;
- goto out;
- }
+ if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
+ return -EBUSY;
+
/* we call try-to-free pages for make this cgroup empty */
lru_add_drain_all();
/* try to free all pages in this cgroup */
- shrink = 1;
while (nr_retries && res_counter_read_u64(&memcg->res, RES_USAGE) > 0) {
int progress;
- if (signal_pending(current)) {
- ret = -EINTR;
- goto out;
- }
+ if (signal_pending(current))
+ return -EINTR;
+
progress = try_to_free_mem_cgroup_pages(memcg, GFP_KERNEL,
false);
if (!progress) {
@@ -3808,13 +3800,23 @@ try_to_free:
}
lru_add_drain();
- /* try move_account...there may be some *locked* pages. */
- goto move_account;
+ mem_cgroup_reparent_charges(memcg);
+
+ return 0;
}
static int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
{
- return mem_cgroup_force_empty(mem_cgroup_from_cont(cont), true);
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
+ int ret;
+
+ if (mem_cgroup_is_root(memcg))
+ return -EINVAL;
+ css_get(&memcg->css);
+ ret = mem_cgroup_force_empty(memcg);
+ css_put(&memcg->css);
+
+ return ret;
}
@@ -5001,11 +5003,11 @@ free_out:
return ERR_PTR(error);
}
-static int mem_cgroup_pre_destroy(struct cgroup *cont)
+static void mem_cgroup_pre_destroy(struct cgroup *cont)
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
- return mem_cgroup_force_empty(memcg, false);
+ mem_cgroup_reparent_charges(memcg);
}
static void mem_cgroup_destroy(struct cgroup *cont)
@@ -5607,7 +5609,6 @@ struct cgroup_subsys mem_cgroup_subsys = {
.base_cftypes = mem_cgroup_files,
.early_init = 0,
.use_id = 1,
- .__DEPRECATED_clear_css_refs = true,
};
#ifdef CONFIG_MEMCG_SWAP