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![Paolo Bonzini](/assets/img/avatar_default.png)
Instead of using array_size or just a multiply, use a function that takes care of both the multiplication and the overflow checks. Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
225 lines
5.1 KiB
C
225 lines
5.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/swap_cgroup.h>
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#include <linux/vmalloc.h>
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#include <linux/mm.h>
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#include <linux/swapops.h> /* depends on mm.h include */
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static DEFINE_MUTEX(swap_cgroup_mutex);
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struct swap_cgroup_ctrl {
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struct page **map;
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unsigned long length;
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spinlock_t lock;
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};
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static struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
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struct swap_cgroup {
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unsigned short id;
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};
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#define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup))
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/*
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* SwapCgroup implements "lookup" and "exchange" operations.
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* In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge
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* against SwapCache. At swap_free(), this is accessed directly from swap.
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*
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* This means,
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* - we have no race in "exchange" when we're accessed via SwapCache because
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* SwapCache(and its swp_entry) is under lock.
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* - When called via swap_free(), there is no user of this entry and no race.
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* Then, we don't need lock around "exchange".
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*
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* TODO: we can push these buffers out to HIGHMEM.
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*/
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/*
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* allocate buffer for swap_cgroup.
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*/
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static int swap_cgroup_prepare(int type)
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{
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struct page *page;
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struct swap_cgroup_ctrl *ctrl;
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unsigned long idx, max;
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ctrl = &swap_cgroup_ctrl[type];
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for (idx = 0; idx < ctrl->length; idx++) {
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page = alloc_page(GFP_KERNEL | __GFP_ZERO);
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if (!page)
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goto not_enough_page;
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ctrl->map[idx] = page;
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if (!(idx % SWAP_CLUSTER_MAX))
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cond_resched();
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}
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return 0;
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not_enough_page:
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max = idx;
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for (idx = 0; idx < max; idx++)
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__free_page(ctrl->map[idx]);
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return -ENOMEM;
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}
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static struct swap_cgroup *__lookup_swap_cgroup(struct swap_cgroup_ctrl *ctrl,
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pgoff_t offset)
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{
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struct page *mappage;
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struct swap_cgroup *sc;
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mappage = ctrl->map[offset / SC_PER_PAGE];
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sc = page_address(mappage);
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return sc + offset % SC_PER_PAGE;
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}
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static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t ent,
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struct swap_cgroup_ctrl **ctrlp)
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{
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pgoff_t offset = swp_offset(ent);
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struct swap_cgroup_ctrl *ctrl;
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ctrl = &swap_cgroup_ctrl[swp_type(ent)];
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if (ctrlp)
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*ctrlp = ctrl;
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return __lookup_swap_cgroup(ctrl, offset);
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}
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/**
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* swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry.
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* @ent: swap entry to be cmpxchged
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* @old: old id
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* @new: new id
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*
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* Returns old id at success, 0 at failure.
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* (There is no mem_cgroup using 0 as its id)
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*/
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unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
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unsigned short old, unsigned short new)
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{
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struct swap_cgroup_ctrl *ctrl;
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struct swap_cgroup *sc;
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unsigned long flags;
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unsigned short retval;
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sc = lookup_swap_cgroup(ent, &ctrl);
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spin_lock_irqsave(&ctrl->lock, flags);
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retval = sc->id;
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if (retval == old)
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sc->id = new;
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else
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retval = 0;
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spin_unlock_irqrestore(&ctrl->lock, flags);
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return retval;
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}
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/**
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* swap_cgroup_record - record mem_cgroup for a set of swap entries
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* @ent: the first swap entry to be recorded into
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* @id: mem_cgroup to be recorded
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* @nr_ents: number of swap entries to be recorded
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*
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* Returns old value at success, 0 at failure.
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* (Of course, old value can be 0.)
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*/
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unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id,
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unsigned int nr_ents)
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{
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struct swap_cgroup_ctrl *ctrl;
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struct swap_cgroup *sc;
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unsigned short old;
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unsigned long flags;
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pgoff_t offset = swp_offset(ent);
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pgoff_t end = offset + nr_ents;
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sc = lookup_swap_cgroup(ent, &ctrl);
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spin_lock_irqsave(&ctrl->lock, flags);
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old = sc->id;
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for (;;) {
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VM_BUG_ON(sc->id != old);
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sc->id = id;
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offset++;
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if (offset == end)
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break;
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if (offset % SC_PER_PAGE)
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sc++;
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else
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sc = __lookup_swap_cgroup(ctrl, offset);
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}
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spin_unlock_irqrestore(&ctrl->lock, flags);
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return old;
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}
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/**
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* lookup_swap_cgroup_id - lookup mem_cgroup id tied to swap entry
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* @ent: swap entry to be looked up.
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*
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* Returns ID of mem_cgroup at success. 0 at failure. (0 is invalid ID)
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*/
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unsigned short lookup_swap_cgroup_id(swp_entry_t ent)
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{
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return lookup_swap_cgroup(ent, NULL)->id;
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}
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int swap_cgroup_swapon(int type, unsigned long max_pages)
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{
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void *array;
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unsigned long length;
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struct swap_cgroup_ctrl *ctrl;
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length = DIV_ROUND_UP(max_pages, SC_PER_PAGE);
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array = vcalloc(length, sizeof(void *));
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if (!array)
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goto nomem;
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ctrl = &swap_cgroup_ctrl[type];
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mutex_lock(&swap_cgroup_mutex);
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ctrl->length = length;
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ctrl->map = array;
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spin_lock_init(&ctrl->lock);
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if (swap_cgroup_prepare(type)) {
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/* memory shortage */
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ctrl->map = NULL;
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ctrl->length = 0;
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mutex_unlock(&swap_cgroup_mutex);
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vfree(array);
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goto nomem;
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}
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mutex_unlock(&swap_cgroup_mutex);
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return 0;
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nomem:
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pr_info("couldn't allocate enough memory for swap_cgroup\n");
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pr_info("swap_cgroup can be disabled by swapaccount=0 boot option\n");
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return -ENOMEM;
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}
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void swap_cgroup_swapoff(int type)
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{
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struct page **map;
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unsigned long i, length;
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struct swap_cgroup_ctrl *ctrl;
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mutex_lock(&swap_cgroup_mutex);
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ctrl = &swap_cgroup_ctrl[type];
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map = ctrl->map;
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length = ctrl->length;
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ctrl->map = NULL;
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ctrl->length = 0;
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mutex_unlock(&swap_cgroup_mutex);
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if (map) {
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for (i = 0; i < length; i++) {
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struct page *page = map[i];
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if (page)
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__free_page(page);
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if (!(i % SWAP_CLUSTER_MAX))
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cond_resched();
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}
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vfree(map);
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}
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}
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