diff options
Diffstat (limited to 'mm/swap_cgroup.c')
| -rw-r--r-- | mm/swap_cgroup.c | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/mm/swap_cgroup.c b/mm/swap_cgroup.c new file mode 100644 index 0000000000..db6c4a26cf --- /dev/null +++ b/mm/swap_cgroup.c @@ -0,0 +1,231 @@ +// 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 length; + struct swap_cgroup_ctrl *ctrl; + + if (mem_cgroup_disabled()) + return 0; + + length = DIV_ROUND_UP(max_pages, SC_PER_PAGE); + + array = vcalloc(length, sizeof(void *)); + 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 (mem_cgroup_disabled()) + 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); + } +} |