v4.19.13 snapshot.
diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c
new file mode 100644
index 0000000..45affae
--- /dev/null
+++ b/mm/swap_cgroup.c
@@ -0,0 +1,233 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/swap_cgroup.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+
+#include <linux/swapops.h> /* depends on mm.h include */
+
+static DEFINE_MUTEX(swap_cgroup_mutex);
+struct swap_cgroup_ctrl {
+ struct page **map;
+ unsigned long length;
+ spinlock_t lock;
+};
+
+static struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
+
+struct swap_cgroup {
+ unsigned short id;
+};
+#define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup))
+
+/*
+ * SwapCgroup implements "lookup" and "exchange" operations.
+ * In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge
+ * against SwapCache. At swap_free(), this is accessed directly from swap.
+ *
+ * This means,
+ * - we have no race in "exchange" when we're accessed via SwapCache because
+ * SwapCache(and its swp_entry) is under lock.
+ * - When called via swap_free(), there is no user of this entry and no race.
+ * Then, we don't need lock around "exchange".
+ *
+ * TODO: we can push these buffers out to HIGHMEM.
+ */
+
+/*
+ * allocate buffer for swap_cgroup.
+ */
+static int swap_cgroup_prepare(int type)
+{
+ struct page *page;
+ struct swap_cgroup_ctrl *ctrl;
+ unsigned long idx, max;
+
+ ctrl = &swap_cgroup_ctrl[type];
+
+ for (idx = 0; idx < ctrl->length; idx++) {
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ goto not_enough_page;
+ ctrl->map[idx] = page;
+
+ if (!(idx % SWAP_CLUSTER_MAX))
+ cond_resched();
+ }
+ return 0;
+not_enough_page:
+ max = idx;
+ for (idx = 0; idx < max; idx++)
+ __free_page(ctrl->map[idx]);
+
+ return -ENOMEM;
+}
+
+static struct swap_cgroup *__lookup_swap_cgroup(struct swap_cgroup_ctrl *ctrl,
+ pgoff_t offset)
+{
+ struct page *mappage;
+ struct swap_cgroup *sc;
+
+ mappage = ctrl->map[offset / SC_PER_PAGE];
+ sc = page_address(mappage);
+ return sc + offset % SC_PER_PAGE;
+}
+
+static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t ent,
+ struct swap_cgroup_ctrl **ctrlp)
+{
+ pgoff_t offset = swp_offset(ent);
+ struct swap_cgroup_ctrl *ctrl;
+
+ ctrl = &swap_cgroup_ctrl[swp_type(ent)];
+ if (ctrlp)
+ *ctrlp = ctrl;
+ return __lookup_swap_cgroup(ctrl, offset);
+}
+
+/**
+ * swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry.
+ * @ent: swap entry to be cmpxchged
+ * @old: old id
+ * @new: new id
+ *
+ * Returns old id at success, 0 at failure.
+ * (There is no mem_cgroup using 0 as its id)
+ */
+unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
+ unsigned short old, unsigned short new)
+{
+ struct swap_cgroup_ctrl *ctrl;
+ struct swap_cgroup *sc;
+ unsigned long flags;
+ unsigned short retval;
+
+ sc = lookup_swap_cgroup(ent, &ctrl);
+
+ spin_lock_irqsave(&ctrl->lock, flags);
+ retval = sc->id;
+ if (retval == old)
+ sc->id = new;
+ else
+ retval = 0;
+ spin_unlock_irqrestore(&ctrl->lock, flags);
+ return retval;
+}
+
+/**
+ * swap_cgroup_record - record mem_cgroup for a set of swap entries
+ * @ent: the first swap entry to be recorded into
+ * @id: mem_cgroup to be recorded
+ * @nr_ents: number of swap entries to be recorded
+ *
+ * Returns old value at success, 0 at failure.
+ * (Of course, old value can be 0.)
+ */
+unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id,
+ unsigned int nr_ents)
+{
+ struct swap_cgroup_ctrl *ctrl;
+ struct swap_cgroup *sc;
+ unsigned short old;
+ unsigned long flags;
+ pgoff_t offset = swp_offset(ent);
+ pgoff_t end = offset + nr_ents;
+
+ sc = lookup_swap_cgroup(ent, &ctrl);
+
+ spin_lock_irqsave(&ctrl->lock, flags);
+ old = sc->id;
+ for (;;) {
+ VM_BUG_ON(sc->id != old);
+ sc->id = id;
+ offset++;
+ if (offset == end)
+ break;
+ if (offset % SC_PER_PAGE)
+ sc++;
+ else
+ sc = __lookup_swap_cgroup(ctrl, offset);
+ }
+ spin_unlock_irqrestore(&ctrl->lock, flags);
+
+ return old;
+}
+
+/**
+ * lookup_swap_cgroup_id - lookup mem_cgroup id tied to swap entry
+ * @ent: swap entry to be looked up.
+ *
+ * Returns ID of mem_cgroup at success. 0 at failure. (0 is invalid ID)
+ */
+unsigned short lookup_swap_cgroup_id(swp_entry_t ent)
+{
+ return lookup_swap_cgroup(ent, NULL)->id;
+}
+
+int swap_cgroup_swapon(int type, unsigned long max_pages)
+{
+ void *array;
+ unsigned long array_size;
+ unsigned long length;
+ struct swap_cgroup_ctrl *ctrl;
+
+ if (!do_swap_account)
+ return 0;
+
+ length = DIV_ROUND_UP(max_pages, SC_PER_PAGE);
+ array_size = length * sizeof(void *);
+
+ array = vzalloc(array_size);
+ if (!array)
+ goto nomem;
+
+ ctrl = &swap_cgroup_ctrl[type];
+ mutex_lock(&swap_cgroup_mutex);
+ ctrl->length = length;
+ ctrl->map = array;
+ spin_lock_init(&ctrl->lock);
+ if (swap_cgroup_prepare(type)) {
+ /* memory shortage */
+ ctrl->map = NULL;
+ ctrl->length = 0;
+ mutex_unlock(&swap_cgroup_mutex);
+ vfree(array);
+ goto nomem;
+ }
+ mutex_unlock(&swap_cgroup_mutex);
+
+ return 0;
+nomem:
+ pr_info("couldn't allocate enough memory for swap_cgroup\n");
+ pr_info("swap_cgroup can be disabled by swapaccount=0 boot option\n");
+ return -ENOMEM;
+}
+
+void swap_cgroup_swapoff(int type)
+{
+ struct page **map;
+ unsigned long i, length;
+ struct swap_cgroup_ctrl *ctrl;
+
+ if (!do_swap_account)
+ return;
+
+ mutex_lock(&swap_cgroup_mutex);
+ ctrl = &swap_cgroup_ctrl[type];
+ map = ctrl->map;
+ length = ctrl->length;
+ ctrl->map = NULL;
+ ctrl->length = 0;
+ mutex_unlock(&swap_cgroup_mutex);
+
+ if (map) {
+ for (i = 0; i < length; i++) {
+ struct page *page = map[i];
+ if (page)
+ __free_page(page);
+ if (!(i % SWAP_CLUSTER_MAX))
+ cond_resched();
+ }
+ vfree(map);
+ }
+}