Merge branch 'akpm' (patches from Andrew)

Merge third patch-bomb from Andrew Morton:

 - even more of the rest of MM

 - lib/ updates

 - checkpatch updates

 - small changes to a few scruffy filesystems

 - kmod fixes/cleanups

 - kexec updates

 - a dma-mapping cleanup series from hch

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (81 commits)
  dma-mapping: consolidate dma_set_mask
  dma-mapping: consolidate dma_supported
  dma-mapping: cosolidate dma_mapping_error
  dma-mapping: consolidate dma_{alloc,free}_noncoherent
  dma-mapping: consolidate dma_{alloc,free}_{attrs,coherent}
  mm: use vma_is_anonymous() in create_huge_pmd() and wp_huge_pmd()
  mm: make sure all file VMAs have ->vm_ops set
  mm, mpx: add "vm_flags_t vm_flags" arg to do_mmap_pgoff()
  mm: mark most vm_operations_struct const
  namei: fix warning while make xmldocs caused by namei.c
  ipc: convert invalid scenarios to use WARN_ON
  zlib_deflate/deftree: remove bi_reverse()
  lib/decompress_unlzma: Do a NULL check for pointer
  lib/decompressors: use real out buf size for gunzip with kernel
  fs/affs: make root lookup from blkdev logical size
  sysctl: fix int -> unsigned long assignments in INT_MIN case
  kexec: export KERNEL_IMAGE_SIZE to vmcoreinfo
  kexec: align crash_notes allocation to make it be inside one physical page
  kexec: remove unnecessary test in kimage_alloc_crash_control_pages()
  kexec: split kexec_load syscall from kexec core code
  ...

19 files changed, 934 insertions, 243 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 3a4070f5ab79..6413d027c0b2 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -649,6 +649,18 @@ config DEFERRED_STRUCT_PAGE_INIT
 	  processes running early in the lifetime of the systemm until kswapd
 	  finishes the initialisation.
 
+config IDLE_PAGE_TRACKING
+	bool "Enable idle page tracking"
+	depends on SYSFS && MMU
+	select PAGE_EXTENSION if !64BIT
+	help
+	  This feature allows to estimate the amount of user pages that have
+	  not been touched during a given period of time. This information can
+	  be useful to tune memory cgroup limits and/or for job placement
+	  within a compute cluster.
+
+	  See Documentation/vm/idle_page_tracking.txt for more details.
+
 config ZONE_DEVICE
 	bool "Device memory (pmem, etc...) hotplug support" if EXPERT
 	default !ZONE_DMA
diff --git a/mm/Makefile b/mm/Makefile
index b424d5e5b6ff..56f8eed73f1a 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -79,3 +79,4 @@ obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
 obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
 obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
 obj-$(CONFIG_USERFAULTFD) += userfaultfd.o
+obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o
diff --git a/mm/debug.c b/mm/debug.c
index 76089ddf99ea..6c1b3ea61bfd 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -48,6 +48,10 @@ static const struct trace_print_flags pageflag_names[] = {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	{1UL << PG_compound_lock,	"compound_lock"	},
 #endif
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
+	{1UL << PG_young,		"young"		},
+	{1UL << PG_idle,		"idle"		},
+#endif
 };
 
 static void dump_flags(unsigned long flags,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b16279cbd91d..4b06b8db9df2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -25,6 +25,7 @@
 #include <linux/migrate.h>
 #include <linux/hashtable.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/page_idle.h>
 
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
@@ -1757,6 +1758,11 @@ static void __split_huge_page_refcount(struct page *page,
 		/* clear PageTail before overwriting first_page */
 		smp_wmb();
 
+		if (page_is_young(page))
+			set_page_young(page_tail);
+		if (page_is_idle(page))
+			set_page_idle(page_tail);
+
 		/*
 		 * __split_huge_page_splitting() already set the
 		 * splitting bit in all pmd that could map this
@@ -2262,7 +2268,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		VM_BUG_ON_PAGE(PageLRU(page), page);
 
 		/* If there is no mapped pte young don't collapse the page */
-		if (pte_young(pteval) || PageReferenced(page) ||
+		if (pte_young(pteval) ||
+		    page_is_young(page) || PageReferenced(page) ||
 		    mmu_notifier_test_young(vma->vm_mm, address))
 			referenced = true;
 	}
@@ -2693,7 +2700,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 		 */
 		if (page_count(page) != 1 + !!PageSwapCache(page))
 			goto out_unmap;
-		if (pte_young(pteval) || PageReferenced(page) ||
+		if (pte_young(pteval) ||
+		    page_is_young(page) || PageReferenced(page) ||
 		    mmu_notifier_test_young(vma->vm_mm, address))
 			referenced = true;
 	}
diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
index aeba0edd6e44..9d26fd9fefe4 100644
--- a/mm/hwpoison-inject.c
+++ b/mm/hwpoison-inject.c
@@ -45,12 +45,9 @@ static int hwpoison_inject(void *data, u64 val)
 	/*
 	 * do a racy check with elevated page count, to make sure PG_hwpoison
 	 * will only be set for the targeted owner (or on a free page).
-	 * We temporarily take page lock for try_get_mem_cgroup_from_page().
 	 * memory_failure() will redo the check reliably inside page lock.
 	 */
-	lock_page(hpage);
 	err = hwpoison_filter(hpage);
-	unlock_page(hpage);
 	if (err)
 		goto put_out;
 
@@ -126,7 +123,7 @@ static int pfn_inject_init(void)
 	if (!dentry)
 		goto fail;
 
-#ifdef CONFIG_MEMCG_SWAP
+#ifdef CONFIG_MEMCG
 	dentry = debugfs_create_u64("corrupt-filter-memcg", 0600,
 				    hwpoison_dir, &hwpoison_filter_memcg);
 	if (!dentry)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index f532f6a37b55..77191eccdc6f 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -302,23 +302,14 @@ static void hex_dump_object(struct seq_file *seq,
 			    struct kmemleak_object *object)
 {
 	const u8 *ptr = (const u8 *)object->pointer;
-	int i, len, remaining;
-	unsigned char linebuf[HEX_ROW_SIZE * 5];
+	size_t len;
 
 	/* limit the number of lines to HEX_MAX_LINES */
-	remaining = len =
-		min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));
-
-	seq_printf(seq, "  hex dump (first %d bytes):\n", len);
-	for (i = 0; i < len; i += HEX_ROW_SIZE) {
-		int linelen = min(remaining, HEX_ROW_SIZE);
-
-		remaining -= HEX_ROW_SIZE;
-		hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE,
-				   HEX_GROUP_SIZE, linebuf, sizeof(linebuf),
-				   HEX_ASCII);
-		seq_printf(seq, "    %s\n", linebuf);
-	}
+	len = min_t(size_t, object->size, HEX_MAX_LINES * HEX_ROW_SIZE);
+
+	seq_printf(seq, "  hex dump (first %zu bytes):\n", len);
+	seq_hex_dump(seq, "    ", DUMP_PREFIX_NONE, HEX_ROW_SIZE,
+		     HEX_GROUP_SIZE, ptr, len, HEX_ASCII);
 }
 
 /*
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1742a2db89c7..6ddaeba34e09 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -441,6 +441,34 @@ struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
 	return &memcg->css;
 }
 
+/**
+ * page_cgroup_ino - return inode number of the memcg a page is charged to
+ * @page: the page
+ *
+ * Look up the closest online ancestor of the memory cgroup @page is charged to
+ * and return its inode number or 0 if @page is not charged to any cgroup. It
+ * is safe to call this function without holding a reference to @page.
+ *
+ * Note, this function is inherently racy, because there is nothing to prevent
+ * the cgroup inode from getting torn down and potentially reallocated a moment
+ * after page_cgroup_ino() returns, so it only should be used by callers that
+ * do not care (such as procfs interfaces).
+ */
+ino_t page_cgroup_ino(struct page *page)
+{
+	struct mem_cgroup *memcg;
+	unsigned long ino = 0;
+
+	rcu_read_lock();
+	memcg = READ_ONCE(page->mem_cgroup);
+	while (memcg && !(memcg->css.flags & CSS_ONLINE))
+		memcg = parent_mem_cgroup(memcg);
+	if (memcg)
+		ino = cgroup_ino(memcg->css.cgroup);
+	rcu_read_unlock();
+	return ino;
+}
+
 static struct mem_cgroup_per_zone *
 mem_cgroup_page_zoneinfo(struct mem_cgroup *memcg, struct page *page)
 {
@@ -2071,40 +2099,6 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
 	css_put_many(&memcg->css, nr_pages);
 }
 
-/*
- * try_get_mem_cgroup_from_page - look up page's memcg association
- * @page: the page
- *
- * Look up, get a css reference, and return the memcg that owns @page.
- *
- * The page must be locked to prevent racing with swap-in and page
- * cache charges.  If coming from an unlocked page table, the caller
- * must ensure the page is on the LRU or this can race with charging.
- */
-struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
-{
-	struct mem_cgroup *memcg;
-	unsigned short id;
-	swp_entry_t ent;
-
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-
-	memcg = page->mem_cgroup;
-	if (memcg) {
-		if (!css_tryget_online(&memcg->css))
-			memcg = NULL;
-	} else if (PageSwapCache(page)) {
-		ent.val = page_private(page);
-		id = lookup_swap_cgroup_id(ent);
-		rcu_read_lock();
-		memcg = mem_cgroup_from_id(id);
-		if (memcg && !css_tryget_online(&memcg->css))
-			memcg = NULL;
-		rcu_read_unlock();
-	}
-	return memcg;
-}
-
 static void lock_page_lru(struct page *page, int *isolated)
 {
 	struct zone *zone = page_zone(page);
@@ -5301,8 +5295,20 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 		 * the page lock, which serializes swap cache removal, which
 		 * in turn serializes uncharging.
 		 */
+		VM_BUG_ON_PAGE(!PageLocked(page), page);
 		if (page->mem_cgroup)
 			goto out;
+
+		if (do_swap_account) {
+			swp_entry_t ent = { .val = page_private(page), };
+			unsigned short id = lookup_swap_cgroup_id(ent);
+
+			rcu_read_lock();
+			memcg = mem_cgroup_from_id(id);
+			if (memcg && !css_tryget_online(&memcg->css))
+				memcg = NULL;
+			rcu_read_unlock();
+		}
 	}
 
 	if (PageTransHuge(page)) {
@@ -5310,8 +5316,6 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 		VM_BUG_ON_PAGE(!PageTransHuge(page), page);
 	}
 
-	if (do_swap_account && PageSwapCache(page))
-		memcg = try_get_mem_cgroup_from_page(page);
 	if (!memcg)
 		memcg = get_mem_cgroup_from_mm(mm);
 
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index eeda6485e76c..95882692e747 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -130,27 +130,15 @@ static int hwpoison_filter_flags(struct page *p)
  * can only guarantee that the page either belongs to the memcg tasks, or is
  * a freed page.
  */
-#ifdef	CONFIG_MEMCG_SWAP
+#ifdef CONFIG_MEMCG
 u64 hwpoison_filter_memcg;
 EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
 static int hwpoison_filter_task(struct page *p)
 {
-	struct mem_cgroup *mem;
-	struct cgroup_subsys_state *css;
-	unsigned long ino;
-
 	if (!hwpoison_filter_memcg)
 		return 0;
 
-	mem = try_get_mem_cgroup_from_page(p);
-	if (!mem)
-		return -EINVAL;
-
-	css = &mem->css;
-	ino = cgroup_ino(css->cgroup);
-	css_put(css);
-
-	if (ino != hwpoison_filter_memcg)
+	if (page_cgroup_ino(p) != hwpoison_filter_memcg)
 		return -EINVAL;
 
 	return 0;
diff --git a/mm/memory.c b/mm/memory.c
index 6cd0b2160401..9cb27470fee9 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3233,7 +3233,7 @@ out:
 static int create_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, pmd_t *pmd, unsigned int flags)
 {
-	if (!vma->vm_ops)
+	if (vma_is_anonymous(vma))
 		return do_huge_pmd_anonymous_page(mm, vma, address, pmd, flags);
 	if (vma->vm_ops->pmd_fault)
 		return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
@@ -3244,7 +3244,7 @@ static int wp_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, pmd_t *pmd, pmd_t orig_pmd,
 			unsigned int flags)
 {
-	if (!vma->vm_ops)
+	if (vma_is_anonymous(vma))
 		return do_huge_pmd_wp_page(mm, vma, address, pmd, orig_pmd);
 	if (vma->vm_ops->pmd_fault)
 		return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
diff --git a/mm/migrate.c b/mm/migrate.c
index 02ce25df16c2..c3cb566af3e2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -37,6 +37,7 @@
 #include <linux/gfp.h>
 #include <linux/balloon_compaction.h>
 #include <linux/mmu_notifier.h>
+#include <linux/page_idle.h>
 
 #include <asm/tlbflush.h>
 
@@ -524,6 +525,11 @@ void migrate_page_copy(struct page *newpage, struct page *page)
 			__set_page_dirty_nobuffers(newpage);
  	}
 
+	if (page_is_young(page))
+		set_page_young(newpage);
+	if (page_is_idle(page))
+		set_page_idle(newpage);
+
 	/*
 	 * Copy NUMA information to the new page, to prevent over-eager
 	 * future migrations of this same page.
diff --git a/mm/mmap.c b/mm/mmap.c
index b6be3249f0a9..971dd2cb77d2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -612,6 +612,8 @@ static unsigned long count_vma_pages_range(struct mm_struct *mm,
 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
 		struct rb_node **rb_link, struct rb_node *rb_parent)
 {
+	WARN_ONCE(vma->vm_file && !vma->vm_ops, "missing vma->vm_ops");
+
 	/* Update tracking information for the gap following the new vma. */
 	if (vma->vm_next)
 		vma_gap_update(vma->vm_next);
@@ -1260,14 +1262,12 @@ static inline int mlock_future_check(struct mm_struct *mm,
 /*
  * The caller must hold down_write(&current->mm->mmap_sem).
  */
-
-unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
+unsigned long do_mmap(struct file *file, unsigned long addr,
 			unsigned long len, unsigned long prot,
-			unsigned long flags, unsigned long pgoff,
-			unsigned long *populate)
+			unsigned long flags, vm_flags_t vm_flags,
+			unsigned long pgoff, unsigned long *populate)
 {
 	struct mm_struct *mm = current->mm;
-	vm_flags_t vm_flags;
 
 	*populate = 0;
 
@@ -1311,7 +1311,7 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 	 * to. we assume access permissions have been handled by the open
 	 * of the memory object, so we don't do any here.
 	 */
-	vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
+	vm_flags |= calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
 			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
 
 	if (flags & MAP_LOCKED)
@@ -1638,6 +1638,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 		 */
 		WARN_ON_ONCE(addr != vma->vm_start);
 
+		/* All file mapping must have ->vm_ops set */
+		if (!vma->vm_ops) {
+			static const struct vm_operations_struct dummy_ops = {};
+			vma->vm_ops = &dummy_ops;
+		}
+
 		addr = vma->vm_start;
 		vm_flags = vma->vm_flags;
 	} else if (vm_flags & VM_SHARED) {
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 3b9b3d0741b2..5fbdd367bbed 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -123,6 +123,23 @@ int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
 	return young;
 }
 
+int __mmu_notifier_clear_young(struct mm_struct *mm,
+			       unsigned long start,
+			       unsigned long end)
+{
+	struct mmu_notifier *mn;
+	int young = 0, id;
+
+	id = srcu_read_lock(&srcu);
+	hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
+		if (mn->ops->clear_young)
+			young |= mn->ops->clear_young(mn, mm, start, end);
+	}
+	srcu_read_unlock(&srcu, id);
+
+	return young;
+}
+
 int __mmu_notifier_test_young(struct mm_struct *mm,
 			      unsigned long address)
 {
diff --git a/mm/nommu.c b/mm/nommu.c
index 1cc0709fcaa5..ab14a2014dea 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1233,18 +1233,19 @@ enomem:
 /*
  * handle mapping creation for uClinux
  */
-unsigned long do_mmap_pgoff(struct file *file,
-			    unsigned long addr,
-			    unsigned long len,
-			    unsigned long prot,
-			    unsigned long flags,
-			    unsigned long pgoff,
-			    unsigned long *populate)
+unsigned long do_mmap(struct file *file,
+			unsigned long addr,
+			unsigned long len,
+			unsigned long prot,
+			unsigned long flags,
+			vm_flags_t vm_flags,
+			unsigned long pgoff,
+			unsigned long *populate)
 {
 	struct vm_area_struct *vma;
 	struct vm_region *region;
 	struct rb_node *rb;
-	unsigned long capabilities, vm_flags, result;
+	unsigned long capabilities, result;
 	int ret;
 
 	*populate = 0;
@@ -1262,7 +1263,7 @@ unsigned long do_mmap_pgoff(struct file *file,
 
 	/* we've determined that we can make the mapping, now translate what we
 	 * now know into VMA flags */
-	vm_flags = determine_vm_flags(file, prot, flags, capabilities);
+	vm_flags |= determine_vm_flags(file, prot, flags, capabilities);
 
 	/* we're going to need to record the mapping */
 	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
diff --git a/mm/page_ext.c b/mm/page_ext.c
index d86fd2f5353f..292ca7b8debd 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -6,6 +6,7 @@
 #include <linux/vmalloc.h>
 #include <linux/kmemleak.h>
 #include <linux/page_owner.h>
+#include <linux/page_idle.h>
 
 /*
  * struct page extension
@@ -59,6 +60,9 @@ static struct page_ext_operations *page_ext_ops[] = {
 #ifdef CONFIG_PAGE_OWNER
 	&page_owner_ops,
 #endif
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
+	&page_idle_ops,
+#endif
 };
 
 static unsigned long total_usage;
diff --git a/mm/page_idle.c b/mm/page_idle.c
new file mode 100644
index 000000000000..d5dd79041484
--- /dev/null
+++ b/mm/page_idle.c
@@ -0,0 +1,232 @@
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/fs.h>
+#include <linux/sysfs.h>
+#include <linux/kobject.h>
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/mmu_notifier.h>
+#include <linux/page_ext.h>
+#include <linux/page_idle.h>
+
+#define BITMAP_CHUNK_SIZE	sizeof(u64)
+#define BITMAP_CHUNK_BITS	(BITMAP_CHUNK_SIZE * BITS_PER_BYTE)
+
+/*
+ * Idle page tracking only considers user memory pages, for other types of
+ * pages the idle flag is always unset and an attempt to set it is silently
+ * ignored.
+ *
+ * We treat a page as a user memory page if it is on an LRU list, because it is
+ * always safe to pass such a page to rmap_walk(), which is essential for idle
+ * page tracking. With such an indicator of user pages we can skip isolated
+ * pages, but since there are not usually many of them, it will hardly affect
+ * the overall result.
+ *
+ * This function tries to get a user memory page by pfn as described above.
+ */
+static struct page *page_idle_get_page(unsigned long pfn)
+{
+	struct page *page;
+	struct zone *zone;
+
+	if (!pfn_valid(pfn))
+		return NULL;
+
+	page = pfn_to_page(pfn);
+	if (!page || !PageLRU(page) ||
+	    !get_page_unless_zero(page))
+		return NULL;
+
+	zone = page_zone(page);
+	spin_lock_irq(&zone->lru_lock);
+	if (unlikely(!PageLRU(page))) {
+		put_page(page);
+		page = NULL;
+	}
+	spin_unlock_irq(&zone->lru_lock);
+	return page;
+}
+
+static int page_idle_clear_pte_refs_one(struct page *page,
+					struct vm_area_struct *vma,
+					unsigned long addr, void *arg)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	spinlock_t *ptl;
+	pmd_t *pmd;
+	pte_t *pte;
+	bool referenced = false;
+
+	if (unlikely(PageTransHuge(page))) {
+		pmd = page_check_address_pmd(page, mm, addr,
+					     PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
+		if (pmd) {
+			referenced = pmdp_clear_young_notify(vma, addr, pmd);
+			spin_unlock(ptl);
+		}
+	} else {
+		pte = page_check_address(page, mm, addr, &ptl, 0);
+		if (pte) {
+			referenced = ptep_clear_young_notify(vma, addr, pte);
+			pte_unmap_unlock(pte, ptl);
+		}
+	}
+	if (referenced) {
+		clear_page_idle(page);
+		/*
+		 * We cleared the referenced bit in a mapping to this page. To
+		 * avoid interference with page reclaim, mark it young so that
+		 * page_referenced() will return > 0.
+		 */
+		set_page_young(page);
+	}
+	return SWAP_AGAIN;
+}
+
+static void page_idle_clear_pte_refs(struct page *page)
+{
+	/*
+	 * Since rwc.arg is unused, rwc is effectively immutable, so we
+	 * can make it static const to save some cycles and stack.
+	 */
+	static const struct rmap_walk_control rwc = {
+		.rmap_one = page_idle_clear_pte_refs_one,
+		.anon_lock = page_lock_anon_vma_read,
+	};
+	bool need_lock;
+
+	if (!page_mapped(page) ||
+	    !page_rmapping(page))
+		return;
+
+	need_lock = !PageAnon(page) || PageKsm(page);
+	if (need_lock && !trylock_page(page))
+		return;
+
+	rmap_walk(page, (struct rmap_walk_control *)&rwc);
+
+	if (need_lock)
+		unlock_page(page);
+}
+
+static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
+				     struct bin_attribute *attr, char *buf,
+				     loff_t pos, size_t count)
+{
+	u64 *out = (u64 *)buf;
+	struct page *page;
+	unsigned long pfn, end_pfn;
+	int bit;
+
+	if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
+		return -EINVAL;
+
+	pfn = pos * BITS_PER_BYTE;
+	if (pfn >= max_pfn)
+		return 0;
+
+	end_pfn = pfn + count * BITS_PER_BYTE;
+	if (end_pfn > max_pfn)
+		end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
+
+	for (; pfn < end_pfn; pfn++) {
+		bit = pfn % BITMAP_CHUNK_BITS;
+		if (!bit)
+			*out = 0ULL;
+		page = page_idle_get_page(pfn);
+		if (page) {
+			if (page_is_idle(page)) {
+				/*
+				 * The page might have been referenced via a
+				 * pte, in which case it is not idle. Clear
+				 * refs and recheck.
+				 */
+				page_idle_clear_pte_refs(page);
+				if (page_is_idle(page))
+					*out |= 1ULL << bit;
+			}
+			put_page(page);
+		}
+		if (bit == BITMAP_CHUNK_BITS - 1)
+			out++;
+		cond_resched();
+	}
+	return (char *)out - buf;
+}
+
+static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
+				      struct bin_attribute *attr, char *buf,
+				      loff_t pos, size_t count)
+{
+	const u64 *in = (u64 *)buf;
+	struct page *page;
+	unsigned long pfn, end_pfn;
+	int bit;
+
+	if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
+		return -EINVAL;
+
+	pfn = pos * BITS_PER_BYTE;
+	if (pfn >= max_pfn)
+		return -ENXIO;
+
+	end_pfn = pfn + count * BITS_PER_BYTE;
+	if (end_pfn > max_pfn)
+		end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
+
+	for (; pfn < end_pfn; pfn++) {
+		bit = pfn % BITMAP_CHUNK_BITS;
+		if ((*in >> bit) & 1) {
+			page = page_idle_get_page(pfn);
+			if (page) {
+				page_idle_clear_pte_refs(page);
+				set_page_idle(page);
+				put_page(page);
+			}
+		}
+		if (bit == BITMAP_CHUNK_BITS - 1)
+			in++;
+		cond_resched();
+	}
+	return (char *)in - buf;
+}
+
+static struct bin_attribute page_idle_bitmap_attr =
+		__BIN_ATTR(bitmap, S_IRUSR | S_IWUSR,
+			   page_idle_bitmap_read, page_idle_bitmap_write, 0);
+
+static struct bin_attribute *page_idle_bin_attrs[] = {
+	&page_idle_bitmap_attr,
+	NULL,
+};
+
+static struct attribute_group page_idle_attr_group = {
+	.bin_attrs = page_idle_bin_attrs,
+	.name = "page_idle",
+};
+
+#ifndef CONFIG_64BIT
+static bool need_page_idle(void)
+{
+	return true;
+}
+struct page_ext_operations page_idle_ops = {
+	.need = need_page_idle,
+};
+#endif
+
+static int __init page_idle_init(void)
+{
+	int err;
+
+	err = sysfs_create_group(mm_kobj, &page_idle_attr_group);
+	if (err) {
+		pr_err("page_idle: register sysfs failed\n");
+		return err;
+	}
+	return 0;
+}
+subsys_initcall(page_idle_init);
diff --git a/mm/rmap.c b/mm/rmap.c
index 0db38e7d0a72..f5b5c1f3dcd7 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -59,6 +59,7 @@
 #include <linux/migrate.h>
 #include <linux/hugetlb.h>
 #include <linux/backing-dev.h>
+#include <linux/page_idle.h>
 
 #include <asm/tlbflush.h>
 
@@ -886,6 +887,11 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
 		pte_unmap_unlock(pte, ptl);
 	}
 
+	if (referenced)
+		clear_page_idle(page);
+	if (test_and_clear_page_young(page))
+		referenced++;
+
 	if (referenced) {
 		pra->referenced++;
 		pra->vm_flags |= vma->vm_flags;
diff --git a/mm/swap.c b/mm/swap.c
index a3a0a2f1f7c3..983f692a47fd 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -32,6 +32,7 @@
 #include <linux/gfp.h>
 #include <linux/uio.h>
 #include <linux/hugetlb.h>
+#include <linux/page_idle.h>
 
 #include "internal.h"
 
@@ -622,6 +623,8 @@ void mark_page_accessed(struct page *page)
 	} else if (!PageReferenced(page)) {
 		SetPageReferenced(page);
 	}
+	if (page_is_idle(page))
+		clear_page_idle(page);
 }
 EXPORT_SYMBOL(mark_page_accessed);
 
diff --git a/mm/zpool.c b/mm/zpool.c
index 68d2dd8ed2d8..8f670d3e8706 100644
--- a/mm/zpool.c
+++ b/mm/zpool.c
@@ -100,6 +100,39 @@ static void zpool_put_driver(struct zpool_driver *driver)
 }
 
 /**
+ * zpool_has_pool() - Check if the pool driver is available
+ * @type	The type of the zpool to check (e.g. zbud, zsmalloc)
+ *
+ * This checks if the @type pool driver is available.  This will try to load
+ * the requested module, if needed, but there is no guarantee the module will
+ * still be loaded and available immediately after calling.  If this returns
+ * true, the caller should assume the pool is available, but must be prepared
+ * to handle the @zpool_create_pool() returning failure.  However if this
+ * returns false, the caller should assume the requested pool type is not
+ * available; either the requested pool type module does not exist, or could
+ * not be loaded, and calling @zpool_create_pool() with the pool type will
+ * fail.
+ *
+ * Returns: true if @type pool is available, false if not
+ */
+bool zpool_has_pool(char *type)
+{
+	struct zpool_driver *driver = zpool_get_driver(type);
+
+	if (!driver) {
+		request_module("zpool-%s", type);
+		driver = zpool_get_driver(type);
+	}
+
+	if (!driver)
+		return false;
+
+	zpool_put_driver(driver);
+	return true;
+}
+EXPORT_SYMBOL(zpool_has_pool);
+
+/**
  * zpool_create_pool() - Create a new zpool
  * @type	The type of the zpool to create (e.g. zbud, zsmalloc)
  * @name	The name of the zpool (e.g. zram0, zswap)
diff --git a/mm/zswap.c b/mm/zswap.c
index 48a1d081e2a5..4043df7c672f 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -80,85 +80,54 @@ static u64 zswap_duplicate_entry;
 static bool zswap_enabled;
 module_param_named(enabled, zswap_enabled, bool, 0644);
 
-/* Compressor to be used by zswap (fixed at boot for now) */
+/* Crypto compressor to use */
 #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
-static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
-module_param_named(compressor, zswap_compressor, charp, 0444);
-
-/* The maximum percentage of memory that the compressed pool can occupy */
-static unsigned int zswap_max_pool_percent = 20;
-module_param_named(max_pool_percent,
-			zswap_max_pool_percent, uint, 0644);
+static char zswap_compressor[CRYPTO_MAX_ALG_NAME] = ZSWAP_COMPRESSOR_DEFAULT;
+static struct kparam_string zswap_compressor_kparam = {
+	.string =	zswap_compressor,
+	.maxlen =	sizeof(zswap_compressor),
+};
+static int zswap_compressor_param_set(const char *,
+				      const struct kernel_param *);
+static struct kernel_param_ops zswap_compressor_param_ops = {
+	.set =		zswap_compressor_param_set,
+	.get =		param_get_string,
+};
+module_param_cb(compressor, &zswap_compressor_param_ops,
+		&zswap_compressor_kparam, 0644);
 
-/* Compressed storage to use */
+/* Compressed storage zpool to use */
 #define ZSWAP_ZPOOL_DEFAULT "zbud"
-static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
-module_param_named(zpool, zswap_zpool_type, charp, 0444);
+static char zswap_zpool_type[32 /* arbitrary */] = ZSWAP_ZPOOL_DEFAULT;
+static struct kparam_string zswap_zpool_kparam = {
+	.string =	zswap_zpool_type,
+	.maxlen =	sizeof(zswap_zpool_type),
+};
+static int zswap_zpool_param_set(const char *, const struct kernel_param *);
+static struct kernel_param_ops zswap_zpool_param_ops = {
+	.set =	zswap_zpool_param_set,
+	.get =	param_get_string,
+};
+module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_kparam, 0644);
 
-/* zpool is shared by all of zswap backend  */
-static struct zpool *zswap_pool;
+/* The maximum percentage of memory that the compressed pool can occupy */
+static unsigned int zswap_max_pool_percent = 20;
+module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
 
 /*********************************
-* compression functions
+* data structures
 **********************************/
-/* per-cpu compression transforms */
-static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
 
-enum comp_op {
-	ZSWAP_COMPOP_COMPRESS,
-	ZSWAP_COMPOP_DECOMPRESS
+struct zswap_pool {
+	struct zpool *zpool;
+	struct crypto_comp * __percpu *tfm;
+	struct kref kref;
+	struct list_head list;
+	struct rcu_head rcu_head;
+	struct notifier_block notifier;
+	char tfm_name[CRYPTO_MAX_ALG_NAME];
 };
 
-static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
-				u8 *dst, unsigned int *dlen)
-{
-	struct crypto_comp *tfm;
-	int ret;
-
-	tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
-	switch (op) {
-	case ZSWAP_COMPOP_COMPRESS:
-		ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
-		break;
-	case ZSWAP_COMPOP_DECOMPRESS:
-		ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
-		break;
-	default:
-		ret = -EINVAL;
-	}
-
-	put_cpu();
-	return ret;
-}
-
-static int __init zswap_comp_init(void)
-{
-	if (!crypto_has_comp(zswap_compressor, 0, 0)) {
-		pr_info("%s compressor not available\n", zswap_compressor);
-		/* fall back to default compressor */
-		zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
-		if (!crypto_has_comp(zswap_compressor, 0, 0))
-			/* can't even load the default compressor */
-			return -ENODEV;
-	}
-	pr_info("using %s compressor\n", zswap_compressor);
-
-	/* alloc percpu transforms */
-	zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
-	if (!zswap_comp_pcpu_tfms)
-		return -ENOMEM;
-	return 0;
-}
-
-static void __init zswap_comp_exit(void)
-{
-	/* free percpu transforms */
-	free_percpu(zswap_comp_pcpu_tfms);
-}
-
-/*********************************
-* data structures
-**********************************/
 /*
  * struct zswap_entry
  *
@@ -166,22 +135,24 @@ static void __init zswap_comp_exit(void)
  * page within zswap.
  *
  * rbnode - links the entry into red-black tree for the appropriate swap type
+ * offset - the swap offset for the entry.  Index into the red-black tree.
  * refcount - the number of outstanding reference to the entry. This is needed
  *            to protect against premature freeing of the entry by code
  *            concurrent calls to load, invalidate, and writeback.  The lock
  *            for the zswap_tree structure that contains the entry must
  *            be held while changing the refcount.  Since the lock must
  *            be held, there is no reason to also make refcount atomic.
- * offset - the swap offset for the entry.  Index into the red-black tree.
- * handle - zpool allocation handle that stores the compressed page data
  * length - the length in bytes of the compressed page data.  Needed during
  *          decompression
+ * pool - the zswap_pool the entry's data is in
+ * handle - zpool allocation handle that stores the compressed page data
  */
 struct zswap_entry {
 	struct rb_node rbnode;
 	pgoff_t offset;
 	int refcount;
 	unsigned int length;
+	struct zswap_pool *pool;
 	unsigned long handle;
 };
 
@@ -201,6 +172,51 @@ struct zswap_tree {
 
 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 
+/* RCU-protected iteration */
+static LIST_HEAD(zswap_pools);
+/* protects zswap_pools list modification */
+static DEFINE_SPINLOCK(zswap_pools_lock);
+
+/* used by param callback function */
+static bool zswap_init_started;
+
+/*********************************
+* helpers and fwd declarations
+**********************************/
+
+#define zswap_pool_debug(msg, p)				\
+	pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,		\
+		 zpool_get_type((p)->zpool))
+
+static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
+static int zswap_pool_get(struct zswap_pool *pool);
+static void zswap_pool_put(struct zswap_pool *pool);
+
+static const struct zpool_ops zswap_zpool_ops = {
+	.evict = zswap_writeback_entry
+};
+
+static bool zswap_is_full(void)
+{
+	return totalram_pages * zswap_max_pool_percent / 100 <
+		DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
+}
+
+static void zswap_update_total_size(void)
+{
+	struct zswap_pool *pool;
+	u64 total = 0;
+
+	rcu_read_lock();
+
+	list_for_each_entry_rcu(pool, &zswap_pools, list)
+		total += zpool_get_total_size(pool->zpool);
+
+	rcu_read_unlock();
+
+	zswap_pool_total_size = total;
+}
+
 /*********************************
 * zswap entry functions
 **********************************/
@@ -294,10 +310,11 @@ static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
  */
 static void zswap_free_entry(struct zswap_entry *entry)
 {
-	zpool_free(zswap_pool, entry->handle);
+	zpool_free(entry->pool->zpool, entry->handle);
+	zswap_pool_put(entry->pool);
 	zswap_entry_cache_free(entry);
 	atomic_dec(&zswap_stored_pages);
-	zswap_pool_total_size = zpool_get_total_size(zswap_pool);
+	zswap_update_total_size();
 }
 
 /* caller must hold the tree lock */
@@ -339,35 +356,21 @@ static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 **********************************/
 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
 
-static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
+static int __zswap_cpu_dstmem_notifier(unsigned long action, unsigned long cpu)
 {
-	struct crypto_comp *tfm;
 	u8 *dst;
 
 	switch (action) {
 	case CPU_UP_PREPARE:
-		tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
-		if (IS_ERR(tfm)) {
-			pr_err("can't allocate compressor transform\n");
-			return NOTIFY_BAD;
-		}
-		*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
 		dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
 		if (!dst) {
 			pr_err("can't allocate compressor buffer\n");
-			crypto_free_comp(tfm);
-			*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
 			return NOTIFY_BAD;
 		}
 		per_cpu(zswap_dstmem, cpu) = dst;
 		break;
 	case CPU_DEAD:
 	case CPU_UP_CANCELED:
-		tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
-		if (tfm) {
-			crypto_free_comp(tfm);
-			*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
-		}
 		dst = per_cpu(zswap_dstmem, cpu);
 		kfree(dst);
 		per_cpu(zswap_dstmem, cpu) = NULL;
@@ -378,43 +381,398 @@ static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
 	return NOTIFY_OK;
 }
 
-static int zswap_cpu_notifier(struct notifier_block *nb,
-				unsigned long action, void *pcpu)
+static int zswap_cpu_dstmem_notifier(struct notifier_block *nb,
+				     unsigned long action, void *pcpu)
 {
-	unsigned long cpu = (unsigned long)pcpu;
-	return __zswap_cpu_notifier(action, cpu);
+	return __zswap_cpu_dstmem_notifier(action, (unsigned long)pcpu);
 }
 
-static struct notifier_block zswap_cpu_notifier_block = {
-	.notifier_call = zswap_cpu_notifier
+static struct notifier_block zswap_dstmem_notifier = {
+	.notifier_call =	zswap_cpu_dstmem_notifier,
 };
 
-static int __init zswap_cpu_init(void)
+static int __init zswap_cpu_dstmem_init(void)
+{
+	unsigned long cpu;
+
+	cpu_notifier_register_begin();
+	for_each_online_cpu(cpu)
+		if (__zswap_cpu_dstmem_notifier(CPU_UP_PREPARE, cpu) ==
+		    NOTIFY_BAD)
+			goto cleanup;
+	__register_cpu_notifier(&zswap_dstmem_notifier);
+	cpu_notifier_register_done();
+	return 0;
+
+cleanup:
+	for_each_online_cpu(cpu)
+		__zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
+	cpu_notifier_register_done();
+	return -ENOMEM;
+}
+
+static void zswap_cpu_dstmem_destroy(void)
+{
+	unsigned long cpu;
+
+	cpu_notifier_register_begin();
+	for_each_online_cpu(cpu)
+		__zswap_cpu_dstmem_notifier(CPU_UP_CANCELED, cpu);
+	__unregister_cpu_notifier(&zswap_dstmem_notifier);
+	cpu_notifier_register_done();
+}
+
+static int __zswap_cpu_comp_notifier(struct zswap_pool *pool,
+				     unsigned long action, unsigned long cpu)
+{
+	struct crypto_comp *tfm;
+
+	switch (action) {
+	case CPU_UP_PREPARE:
+		if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
+			break;
+		tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
+		if (IS_ERR_OR_NULL(tfm)) {
+			pr_err("could not alloc crypto comp %s : %ld\n",
+			       pool->tfm_name, PTR_ERR(tfm));
+			return NOTIFY_BAD;
+		}
+		*per_cpu_ptr(pool->tfm, cpu) = tfm;
+		break;
+	case CPU_DEAD:
+	case CPU_UP_CANCELED:
+		tfm = *per_cpu_ptr(pool->tfm, cpu);
+		if (!IS_ERR_OR_NULL(tfm))
+			crypto_free_comp(tfm);
+		*per_cpu_ptr(pool->tfm, cpu) = NULL;
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static int zswap_cpu_comp_notifier(struct notifier_block *nb,
+				   unsigned long action, void *pcpu)
+{
+	unsigned long cpu = (unsigned long)pcpu;
+	struct zswap_pool *pool = container_of(nb, typeof(*pool), notifier);
+
+	return __zswap_cpu_comp_notifier(pool, action, cpu);
+}
+
+static int zswap_cpu_comp_init(struct zswap_pool *pool)
 {
 	unsigned long cpu;
 
+	memset(&pool->notifier, 0, sizeof(pool->notifier));
+	pool->notifier.notifier_call = zswap_cpu_comp_notifier;
+
 	cpu_notifier_register_begin();
 	for_each_online_cpu(cpu)
-		if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
+		if (__zswap_cpu_comp_notifier(pool, CPU_UP_PREPARE, cpu) ==
+		    NOTIFY_BAD)
 			goto cleanup;
-	__register_cpu_notifier(&zswap_cpu_notifier_block);
+	__register_cpu_notifier(&pool->notifier);
 	cpu_notifier_register_done();
 	return 0;
 
 cleanup:
 	for_each_online_cpu(cpu)
-		__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
+		__zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
 	cpu_notifier_register_done();
 	return -ENOMEM;
 }
 
+static void zswap_cpu_comp_destroy(struct zswap_pool *pool)
+{
+	unsigned long cpu;
+
+	cpu_notifier_register_begin();
+	for_each_online_cpu(cpu)
+		__zswap_cpu_comp_notifier(pool, CPU_UP_CANCELED, cpu);
+	__unregister_cpu_notifier(&pool->notifier);
+	cpu_notifier_register_done();
+}
+
 /*********************************
-* helpers
+* pool functions
 **********************************/
-static bool zswap_is_full(void)
+
+static struct zswap_pool *__zswap_pool_current(void)
 {
-	return totalram_pages * zswap_max_pool_percent / 100 <
-		DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
+	struct zswap_pool *pool;
+
+	pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
+	WARN_ON(!pool);
+
+	return pool;
+}
+
+static struct zswap_pool *zswap_pool_current(void)
+{
+	assert_spin_locked(&zswap_pools_lock);
+
+	return __zswap_pool_current();
+}
+
+static struct zswap_pool *zswap_pool_current_get(void)
+{
+	struct zswap_pool *pool;
+
+	rcu_read_lock();
+
+	pool = __zswap_pool_current();
+	if (!pool || !zswap_pool_get(pool))
+		pool = NULL;
+
+	rcu_read_unlock();
+
+	return pool;
+}
+
+static struct zswap_pool *zswap_pool_last_get(void)
+{
+	struct zswap_pool *pool, *last = NULL;
+
+	rcu_read_lock();
+
+	list_for_each_entry_rcu(pool, &zswap_pools, list)
+		last = pool;
+	if (!WARN_ON(!last) && !zswap_pool_get(last))
+		last = NULL;
+
+	rcu_read_unlock();
+
+	return last;
+}
+
+static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
+{
+	struct zswap_pool *pool;
+
+	assert_spin_locked(&zswap_pools_lock);
+
+	list_for_each_entry_rcu(pool, &zswap_pools, list) {
+		if (strncmp(pool->tfm_name, compressor, sizeof(pool->tfm_name)))
+			continue;
+		if (strncmp(zpool_get_type(pool->zpool), type,
+			    sizeof(zswap_zpool_type)))
+			continue;
+		/* if we can't get it, it's about to be destroyed */
+		if (!zswap_pool_get(pool))
+			continue;
+		return pool;
+	}
+
+	return NULL;
+}
+
+static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
+{
+	struct zswap_pool *pool;
+	gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN;
+
+	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
+	if (!pool) {
+		pr_err("pool alloc failed\n");
+		return NULL;
+	}
+
+	pool->zpool = zpool_create_pool(type, "zswap", gfp, &zswap_zpool_ops);
+	if (!pool->zpool) {
+		pr_err("%s zpool not available\n", type);
+		goto error;
+	}
+	pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
+
+	strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
+	pool->tfm = alloc_percpu(struct crypto_comp *);
+	if (!pool->tfm) {
+		pr_err("percpu alloc failed\n");
+		goto error;
+	}
+
+	if (zswap_cpu_comp_init(pool))
+		goto error;
+	pr_debug("using %s compressor\n", pool->tfm_name);
+
+	/* being the current pool takes 1 ref; this func expects the
+	 * caller to always add the new pool as the current pool
+	 */
+	kref_init(&pool->kref);
+	INIT_LIST_HEAD(&pool->list);
+
+	zswap_pool_debug("created", pool);
+
+	return pool;
+
+error:
+	free_percpu(pool->tfm);
+	if (pool->zpool)
+		zpool_destroy_pool(pool->zpool);
+	kfree(pool);
+	return NULL;
+}
+
+static struct zswap_pool *__zswap_pool_create_fallback(void)
+{
+	if (!crypto_has_comp(zswap_compressor, 0, 0)) {
+		pr_err("compressor %s not available, using default %s\n",
+		       zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
+		strncpy(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT,
+			sizeof(zswap_compressor));
+	}
+	if (!zpool_has_pool(zswap_zpool_type)) {
+		pr_err("zpool %s not available, using default %s\n",
+		       zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
+		strncpy(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT,
+			sizeof(zswap_zpool_type));
+	}
+
+	return zswap_pool_create(zswap_zpool_type, zswap_compressor);
+}
+
+static void zswap_pool_destroy(struct zswap_pool *pool)
+{
+	zswap_pool_debug("destroying", pool);
+
+	zswap_cpu_comp_destroy(pool);
+	free_percpu(pool->tfm);
+	zpool_destroy_pool(pool->zpool);
+	kfree(pool);
+}
+
+static int __must_check zswap_pool_get(struct zswap_pool *pool)
+{
+	return kref_get_unless_zero(&pool->kref);
+}
+
+static void __zswap_pool_release(struct rcu_head *head)
+{
+	struct zswap_pool *pool = container_of(head, typeof(*pool), rcu_head);
+
+	/* nobody should have been able to get a kref... */
+	WARN_ON(kref_get_unless_zero(&pool->kref));
+
+	/* pool is now off zswap_pools list and has no references. */
+	zswap_pool_destroy(pool);
+}
+
+static void __zswap_pool_empty(struct kref *kref)
+{
+	struct zswap_pool *pool;
+
+	pool = container_of(kref, typeof(*pool), kref);
+
+	spin_lock(&zswap_pools_lock);
+
+	WARN_ON(pool == zswap_pool_current());
+
+	list_del_rcu(&pool->list);
+	call_rcu(&pool->rcu_head, __zswap_pool_release);
+
+	spin_unlock(&zswap_pools_lock);
+}
+
+static void zswap_pool_put(struct zswap_pool *pool)
+{
+	kref_put(&pool->kref, __zswap_pool_empty);
+}
+
+/*********************************
+* param callbacks
+**********************************/
+
+static int __zswap_param_set(const char *val, const struct kernel_param *kp,
+			     char *type, char *compressor)
+{
+	struct zswap_pool *pool, *put_pool = NULL;
+	char str[kp->str->maxlen], *s;
+	int ret;
+
+	/*
+	 * kp is either zswap_zpool_kparam or zswap_compressor_kparam, defined
+	 * at the top of this file, so maxlen is CRYPTO_MAX_ALG_NAME (64) or
+	 * 32 (arbitrary).
+	 */
+	strlcpy(str, val, kp->str->maxlen);
+	s = strim(str);
+
+	/* if this is load-time (pre-init) param setting,
+	 * don't create a pool; that's done during init.
+	 */
+	if (!zswap_init_started)
+		return param_set_copystring(s, kp);
+
+	/* no change required */
+	if (!strncmp(kp->str->string, s, kp->str->maxlen))
+		return 0;
+
+	if (!type) {
+		type = s;
+		if (!zpool_has_pool(type)) {
+			pr_err("zpool %s not available\n", type);
+			return -ENOENT;
+		}
+	} else if (!compressor) {
+		compressor = s;
+		if (!crypto_has_comp(compressor, 0, 0)) {
+			pr_err("compressor %s not available\n", compressor);
+			return -ENOENT;
+		}
+	}
+
+	spin_lock(&zswap_pools_lock);
+
+	pool = zswap_pool_find_get(type, compressor);
+	if (pool) {
+		zswap_pool_debug("using existing", pool);
+		list_del_rcu(&pool->list);
+	} else {
+		spin_unlock(&zswap_pools_lock);
+		pool = zswap_pool_create(type, compressor);
+		spin_lock(&zswap_pools_lock);
+	}
+
+	if (pool)
+		ret = param_set_copystring(s, kp);
+	else
+		ret = -EINVAL;
+
+	if (!ret) {
+		put_pool = zswap_pool_current();
+		list_add_rcu(&pool->list, &zswap_pools);
+	} else if (pool) {
+		/* add the possibly pre-existing pool to the end of the pools
+		 * list; if it's new (and empty) then it'll be removed and
+		 * destroyed by the put after we drop the lock
+		 */
+		list_add_tail_rcu(&pool->list, &zswap_pools);
+		put_pool = pool;
+	}
+
+	spin_unlock(&zswap_pools_lock);
+
+	/* drop the ref from either the old current pool,
+	 * or the new pool we failed to add
+	 */
+	if (put_pool)
+		zswap_pool_put(put_pool);
+
+	return ret;
+}
+
+static int zswap_compressor_param_set(const char *val,
+				      const struct kernel_param *kp)
+{
+	return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
+}
+
+static int zswap_zpool_param_set(const char *val,
+				 const struct kernel_param *kp)
+{
+	return __zswap_param_set(val, kp, NULL, zswap_compressor);
 }
 
 /*********************************
@@ -477,6 +835,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 	pgoff_t offset;
 	struct zswap_entry *entry;
 	struct page *page;
+	struct crypto_comp *tfm;
 	u8 *src, *dst;
 	unsigned int dlen;
 	int ret;
@@ -517,13 +876,15 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 	case ZSWAP_SWAPCACHE_NEW: /* page is locked */
 		/* decompress */
 		dlen = PAGE_SIZE;
-		src = (u8 *)zpool_map_handle(zswap_pool, entry->handle,
+		src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
 				ZPOOL_MM_RO) + sizeof(struct zswap_header);
 		dst = kmap_atomic(page);
-		ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
-				entry->length, dst, &dlen);
+		tfm = *get_cpu_ptr(entry->pool->tfm);
+		ret = crypto_comp_decompress(tfm, src, entry->length,
+					     dst, &dlen);
+		put_cpu_ptr(entry->pool->tfm);
 		kunmap_atomic(dst);
-		zpool_unmap_handle(zswap_pool, entry->handle);
+		zpool_unmap_handle(entry->pool->zpool, entry->handle);
 		BUG_ON(ret);
 		BUG_ON(dlen != PAGE_SIZE);
 
@@ -572,6 +933,22 @@ end:
 	return ret;
 }
 
+static int zswap_shrink(void)
+{
+	struct zswap_pool *pool;
+	int ret;
+
+	pool = zswap_pool_last_get();
+	if (!pool)
+		return -ENOENT;
+
+	ret = zpool_shrink(pool->zpool, 1, NULL);
+
+	zswap_pool_put(pool);
+
+	return ret;
+}
+
 /*********************************
 * frontswap hooks
 **********************************/
@@ -581,6 +958,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 {
 	struct zswap_tree *tree = zswap_trees[type];
 	struct zswap_entry *entry, *dupentry;
+	struct crypto_comp *tfm;
 	int ret;
 	unsigned int dlen = PAGE_SIZE, len;
 	unsigned long handle;
@@ -596,7 +974,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 	/* reclaim space if needed */
 	if (zswap_is_full()) {
 		zswap_pool_limit_hit++;
-		if (zpool_shrink(zswap_pool, 1, NULL)) {
+		if (zswap_shrink()) {
 			zswap_reject_reclaim_fail++;
 			ret = -ENOMEM;
 			goto reject;
@@ -611,33 +989,42 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 		goto reject;
 	}
 
+	/* if entry is successfully added, it keeps the reference */
+	entry->pool = zswap_pool_current_get();
+	if (!entry->pool) {
+		ret = -EINVAL;
+		goto freepage;
+	}
+
 	/* compress */
 	dst = get_cpu_var(zswap_dstmem);
+	tfm = *get_cpu_ptr(entry->pool->tfm);
 	src = kmap_atomic(page);
-	ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
+	ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
 	kunmap_atomic(src);
+	put_cpu_ptr(entry->pool->tfm);
 	if (ret) {
 		ret = -EINVAL;
-		goto freepage;
+		goto put_dstmem;
 	}
 
 	/* store */
 	len = dlen + sizeof(struct zswap_header);
-	ret = zpool_malloc(zswap_pool, len, __GFP_NORETRY | __GFP_NOWARN,
-		&handle);
+	ret = zpool_malloc(entry->pool->zpool, len,
+			   __GFP_NORETRY | __GFP_NOWARN, &handle);
 	if (ret == -ENOSPC) {
 		zswap_reject_compress_poor++;
-		goto freepage;
+		goto put_dstmem;
 	}
 	if (ret) {
 		zswap_reject_alloc_fail++;
-		goto freepage;
+		goto put_dstmem;
 	}
-	zhdr = zpool_map_handle(zswap_pool, handle, ZPOOL_MM_RW);
+	zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
 	zhdr->swpentry = swp_entry(type, offset);
 	buf = (u8 *)(zhdr + 1);
 	memcpy(buf, dst, dlen);
-	zpool_unmap_handle(zswap_pool, handle);
+	zpool_unmap_handle(entry->pool->zpool, handle);
 	put_cpu_var(zswap_dstmem);
 
 	/* populate entry */
@@ -660,12 +1047,14 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 
 	/* update stats */
 	atomic_inc(&zswap_stored_pages);
-	zswap_pool_total_size = zpool_get_total_size(zswap_pool);
+	zswap_update_total_size();
 
 	return 0;
 
-freepage:
+put_dstmem:
 	put_cpu_var(zswap_dstmem);
+	zswap_pool_put(entry->pool);
+freepage:
 	zswap_entry_cache_free(entry);
 reject:
 	return ret;
@@ -680,6 +1069,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 {
 	struct zswap_tree *tree = zswap_trees[type];
 	struct zswap_entry *entry;
+	struct crypto_comp *tfm;
 	u8 *src, *dst;
 	unsigned int dlen;
 	int ret;
@@ -696,13 +1086,14 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 
 	/* decompress */
 	dlen = PAGE_SIZE;
-	src = (u8 *)zpool_map_handle(zswap_pool, entry->handle,
+	src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
 			ZPOOL_MM_RO) + sizeof(struct zswap_header);
 	dst = kmap_atomic(page);
-	ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
-		dst, &dlen);
+	tfm = *get_cpu_ptr(entry->pool->tfm);
+	ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
+	put_cpu_ptr(entry->pool->tfm);
 	kunmap_atomic(dst);
-	zpool_unmap_handle(zswap_pool, entry->handle);
+	zpool_unmap_handle(entry->pool->zpool, entry->handle);
 	BUG_ON(ret);
 
 	spin_lock(&tree->lock);
@@ -755,10 +1146,6 @@ static void zswap_frontswap_invalidate_area(unsigned type)
 	zswap_trees[type] = NULL;
 }
 
-static const struct zpool_ops zswap_zpool_ops = {
-	.evict = zswap_writeback_entry
-};
-
 static void zswap_frontswap_init(unsigned type)
 {
 	struct zswap_tree *tree;
@@ -839,49 +1226,40 @@ static void __exit zswap_debugfs_exit(void) { }
 **********************************/
 static int __init init_zswap(void)
 {
-	gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN;
+	struct zswap_pool *pool;
 
-	pr_info("loading zswap\n");
-
-	zswap_pool = zpool_create_pool(zswap_zpool_type, "zswap", gfp,
-					&zswap_zpool_ops);
-	if (!zswap_pool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
-		pr_info("%s zpool not available\n", zswap_zpool_type);
-		zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
-		zswap_pool = zpool_create_pool(zswap_zpool_type, "zswap", gfp,
-					&zswap_zpool_ops);
-	}
-	if (!zswap_pool) {
-		pr_err("%s zpool not available\n", zswap_zpool_type);
-		pr_err("zpool creation failed\n");
-		goto error;
-	}
-	pr_info("using %s pool\n", zswap_zpool_type);
+	zswap_init_started = true;
 
 	if (zswap_entry_cache_create()) {
 		pr_err("entry cache creation failed\n");
-		goto cachefail;
+		goto cache_fail;
 	}
-	if (zswap_comp_init()) {
-		pr_err("compressor initialization failed\n");
-		goto compfail;
+
+	if (zswap_cpu_dstmem_init()) {
+		pr_err("dstmem alloc failed\n");
+		goto dstmem_fail;
 	}
-	if (zswap_cpu_init()) {
-		pr_err("per-cpu initialization failed\n");
-		goto pcpufail;
+
+	pool = __zswap_pool_create_fallback();
+	if (!pool) {
+		pr_err("pool creation failed\n");
+		goto pool_fail;
 	}
+	pr_info("loaded using pool %s/%s\n", pool->tfm_name,
+		zpool_get_type(pool->zpool));
+
+	list_add(&pool->list, &zswap_pools);
 
 	frontswap_register_ops(&zswap_frontswap_ops);
 	if (zswap_debugfs_init())
 		pr_warn("debugfs initialization failed\n");
 	return 0;
-pcpufail:
-	zswap_comp_exit();
-compfail:
+
+pool_fail:
+	zswap_cpu_dstmem_destroy();
+dstmem_fail:
 	zswap_entry_cache_destroy();
-cachefail:
-	zpool_destroy_pool(zswap_pool);
-error:
+cache_fail:
 	return -ENOMEM;
 }
 /* must be late so crypto has time to come up */