1 files changed, 935 insertions, 451 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 6772e0c654fa..54c57103715f 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -33,6 +33,7 @@
 #include <linux/debugfs.h>
 #include <linux/cpuhotplug.h>
 #include <linux/part_stat.h>
+#include <linux/kernel_read_file.h>
 
 #include "zram_drv.h"
 
@@ -43,6 +44,8 @@ static DEFINE_MUTEX(zram_index_mutex);
 static int zram_major;
 static const char *default_compressor = CONFIG_ZRAM_DEF_COMP;
 
+#define ZRAM_MAX_ALGO_NAME_SZ	128
+
 /* Module params (documentation at end) */
 static unsigned int num_devices = 1;
 /*
@@ -54,22 +57,59 @@ static size_t huge_class_size;
 static const struct block_device_operations zram_devops;
 
 static void zram_free_page(struct zram *zram, size_t index);
-static int zram_read_page(struct zram *zram, struct page *page, u32 index,
-			  struct bio *parent);
+static int zram_read_from_zspool(struct zram *zram, struct page *page,
+				 u32 index);
+
+#define slot_dep_map(zram, index) (&(zram)->table[(index)].dep_map)
+
+static void zram_slot_lock_init(struct zram *zram, u32 index)
+{
+	static struct lock_class_key __key;
+
+	lockdep_init_map(slot_dep_map(zram, index), "zram->table[index].lock",
+			 &__key, 0);
+}
 
-static int zram_slot_trylock(struct zram *zram, u32 index)
+/*
+ * entry locking rules:
+ *
+ * 1) Lock is exclusive
+ *
+ * 2) lock() function can sleep waiting for the lock
+ *
+ * 3) Lock owner can sleep
+ *
+ * 4) Use TRY lock variant when in atomic context
+ *    - must check return value and handle locking failers
+ */
+static __must_check bool zram_slot_trylock(struct zram *zram, u32 index)
 {
-	return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags);
+	unsigned long *lock = &zram->table[index].flags;
+
+	if (!test_and_set_bit_lock(ZRAM_ENTRY_LOCK, lock)) {
+		mutex_acquire(slot_dep_map(zram, index), 0, 1, _RET_IP_);
+		lock_acquired(slot_dep_map(zram, index), _RET_IP_);
+		return true;
+	}
+
+	return false;
 }
 
 static void zram_slot_lock(struct zram *zram, u32 index)
 {
-	bit_spin_lock(ZRAM_LOCK, &zram->table[index].flags);
+	unsigned long *lock = &zram->table[index].flags;
+
+	mutex_acquire(slot_dep_map(zram, index), 0, 0, _RET_IP_);
+	wait_on_bit_lock(lock, ZRAM_ENTRY_LOCK, TASK_UNINTERRUPTIBLE);
+	lock_acquired(slot_dep_map(zram, index), _RET_IP_);
 }
 
 static void zram_slot_unlock(struct zram *zram, u32 index)
 {
-	bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags);
+	unsigned long *lock = &zram->table[index].flags;
+
+	mutex_release(slot_dep_map(zram, index), _RET_IP_);
+	clear_and_wake_up_bit(ZRAM_ENTRY_LOCK, lock);
 }
 
 static inline bool init_done(struct zram *zram)
@@ -92,7 +132,6 @@ static void zram_set_handle(struct zram *zram, u32 index, unsigned long handle)
 	zram->table[index].handle = handle;
 }
 
-/* flag operations require table entry bit_spin_lock() being held */
 static bool zram_test_flag(struct zram *zram, u32 index,
 			enum zram_pageflags flag)
 {
@@ -111,17 +150,6 @@ static void zram_clear_flag(struct zram *zram, u32 index,
 	zram->table[index].flags &= ~BIT(flag);
 }
 
-static inline void zram_set_element(struct zram *zram, u32 index,
-			unsigned long element)
-{
-	zram->table[index].element = element;
-}
-
-static unsigned long zram_get_element(struct zram *zram, u32 index)
-{
-	return zram->table[index].element;
-}
-
 static size_t zram_get_obj_size(struct zram *zram, u32 index)
 {
 	return zram->table[index].flags & (BIT(ZRAM_FLAG_SHIFT) - 1);
@@ -142,6 +170,27 @@ static inline bool zram_allocated(struct zram *zram, u32 index)
 			zram_test_flag(zram, index, ZRAM_WB);
 }
 
+static inline void update_used_max(struct zram *zram, const unsigned long pages)
+{
+	unsigned long cur_max = atomic_long_read(&zram->stats.max_used_pages);
+
+	do {
+		if (cur_max >= pages)
+			return;
+	} while (!atomic_long_try_cmpxchg(&zram->stats.max_used_pages,
+					  &cur_max, pages));
+}
+
+static bool zram_can_store_page(struct zram *zram)
+{
+	unsigned long alloced_pages;
+
+	alloced_pages = zs_get_total_pages(zram->mem_pool);
+	update_used_max(zram, alloced_pages);
+
+	return !zram->limit_pages || alloced_pages <= zram->limit_pages;
+}
+
 #if PAGE_SIZE != 4096
 static inline bool is_partial_io(struct bio_vec *bvec)
 {
@@ -177,22 +226,113 @@ static inline u32 zram_get_priority(struct zram *zram, u32 index)
 static void zram_accessed(struct zram *zram, u32 index)
 {
 	zram_clear_flag(zram, index, ZRAM_IDLE);
+	zram_clear_flag(zram, index, ZRAM_PP_SLOT);
 #ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
 	zram->table[index].ac_time = ktime_get_boottime();
 #endif
 }
 
-static inline void update_used_max(struct zram *zram,
-					const unsigned long pages)
+#if defined CONFIG_ZRAM_WRITEBACK || defined CONFIG_ZRAM_MULTI_COMP
+struct zram_pp_slot {
+	unsigned long		index;
+	struct list_head	entry;
+};
+
+/*
+ * A post-processing bucket is, essentially, a size class, this defines
+ * the range (in bytes) of pp-slots sizes in particular bucket.
+ */
+#define PP_BUCKET_SIZE_RANGE	64
+#define NUM_PP_BUCKETS		((PAGE_SIZE / PP_BUCKET_SIZE_RANGE) + 1)
+
+struct zram_pp_ctl {
+	struct list_head	pp_buckets[NUM_PP_BUCKETS];
+};
+
+static struct zram_pp_ctl *init_pp_ctl(void)
 {
-	unsigned long cur_max = atomic_long_read(&zram->stats.max_used_pages);
+	struct zram_pp_ctl *ctl;
+	u32 idx;
 
-	do {
-		if (cur_max >= pages)
-			return;
-	} while (!atomic_long_try_cmpxchg(&zram->stats.max_used_pages,
-					  &cur_max, pages));
+	ctl = kmalloc(sizeof(*ctl), GFP_KERNEL);
+	if (!ctl)
+		return NULL;
+
+	for (idx = 0; idx < NUM_PP_BUCKETS; idx++)
+		INIT_LIST_HEAD(&ctl->pp_buckets[idx]);
+	return ctl;
+}
+
+static void release_pp_slot(struct zram *zram, struct zram_pp_slot *pps)
+{
+	list_del_init(&pps->entry);
+
+	zram_slot_lock(zram, pps->index);
+	zram_clear_flag(zram, pps->index, ZRAM_PP_SLOT);
+	zram_slot_unlock(zram, pps->index);
+
+	kfree(pps);
+}
+
+static void release_pp_ctl(struct zram *zram, struct zram_pp_ctl *ctl)
+{
+	u32 idx;
+
+	if (!ctl)
+		return;
+
+	for (idx = 0; idx < NUM_PP_BUCKETS; idx++) {
+		while (!list_empty(&ctl->pp_buckets[idx])) {
+			struct zram_pp_slot *pps;
+
+			pps = list_first_entry(&ctl->pp_buckets[idx],
+					       struct zram_pp_slot,
+					       entry);
+			release_pp_slot(zram, pps);
+		}
+	}
+
+	kfree(ctl);
+}
+
+static bool place_pp_slot(struct zram *zram, struct zram_pp_ctl *ctl,
+			  u32 index)
+{
+	struct zram_pp_slot *pps;
+	u32 bid;
+
+	pps = kmalloc(sizeof(*pps), GFP_NOIO | __GFP_NOWARN);
+	if (!pps)
+		return false;
+
+	INIT_LIST_HEAD(&pps->entry);
+	pps->index = index;
+
+	bid = zram_get_obj_size(zram, pps->index) / PP_BUCKET_SIZE_RANGE;
+	list_add(&pps->entry, &ctl->pp_buckets[bid]);
+
+	zram_set_flag(zram, pps->index, ZRAM_PP_SLOT);
+	return true;
+}
+
+static struct zram_pp_slot *select_pp_slot(struct zram_pp_ctl *ctl)
+{
+	struct zram_pp_slot *pps = NULL;
+	s32 idx = NUM_PP_BUCKETS - 1;
+
+	/* The higher the bucket id the more optimal slot post-processing is */
+	while (idx >= 0) {
+		pps = list_first_entry_or_null(&ctl->pp_buckets[idx],
+					       struct zram_pp_slot,
+					       entry);
+		if (pps)
+			break;
+
+		idx--;
+	}
+	return pps;
 }
+#endif
 
 static inline void zram_fill_page(void *ptr, unsigned long len,
 					unsigned long value)
@@ -295,19 +435,28 @@ static void mark_idle(struct zram *zram, ktime_t cutoff)
 
 	for (index = 0; index < nr_pages; index++) {
 		/*
-		 * Do not mark ZRAM_UNDER_WB slot as ZRAM_IDLE to close race.
-		 * See the comment in writeback_store.
+		 * Do not mark ZRAM_SAME slots as ZRAM_IDLE, because no
+		 * post-processing (recompress, writeback) happens to the
+		 * ZRAM_SAME slot.
+		 *
+		 * And ZRAM_WB slots simply cannot be ZRAM_IDLE.
 		 */
 		zram_slot_lock(zram, index);
-		if (zram_allocated(zram, index) &&
-				!zram_test_flag(zram, index, ZRAM_UNDER_WB)) {
+		if (!zram_allocated(zram, index) ||
+		    zram_test_flag(zram, index, ZRAM_WB) ||
+		    zram_test_flag(zram, index, ZRAM_SAME)) {
+			zram_slot_unlock(zram, index);
+			continue;
+		}
+
 #ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
-			is_idle = !cutoff || ktime_after(cutoff,
-							 zram->table[index].ac_time);
+		is_idle = !cutoff ||
+			ktime_after(cutoff, zram->table[index].ac_time);
 #endif
-			if (is_idle)
-				zram_set_flag(zram, index, ZRAM_IDLE);
-		}
+		if (is_idle)
+			zram_set_flag(zram, index, ZRAM_IDLE);
+		else
+			zram_clear_flag(zram, index, ZRAM_IDLE);
 		zram_slot_unlock(zram, index);
 	}
 }
@@ -426,11 +575,10 @@ static void reset_bdev(struct zram *zram)
 	if (!zram->backing_dev)
 		return;
 
-	bdev_release(zram->bdev_handle);
 	/* hope filp_close flush all of IO */
 	filp_close(zram->backing_dev, NULL);
 	zram->backing_dev = NULL;
-	zram->bdev_handle = NULL;
+	zram->bdev = NULL;
 	zram->disk->fops = &zram_devops;
 	kvfree(zram->bitmap);
 	zram->bitmap = NULL;
@@ -473,10 +621,8 @@ static ssize_t backing_dev_store(struct device *dev,
 	size_t sz;
 	struct file *backing_dev = NULL;
 	struct inode *inode;
-	struct address_space *mapping;
 	unsigned int bitmap_sz;
 	unsigned long nr_pages, *bitmap = NULL;
-	struct bdev_handle *bdev_handle = NULL;
 	int err;
 	struct zram *zram = dev_to_zram(dev);
 
@@ -497,15 +643,14 @@ static ssize_t backing_dev_store(struct device *dev,
 	if (sz > 0 && file_name[sz - 1] == '\n')
 		file_name[sz - 1] = 0x00;
 
-	backing_dev = filp_open(file_name, O_RDWR|O_LARGEFILE, 0);
+	backing_dev = filp_open(file_name, O_RDWR | O_LARGEFILE | O_EXCL, 0);
 	if (IS_ERR(backing_dev)) {
 		err = PTR_ERR(backing_dev);
 		backing_dev = NULL;
 		goto out;
 	}
 
-	mapping = backing_dev->f_mapping;
-	inode = mapping->host;
+	inode = backing_dev->f_mapping->host;
 
 	/* Support only block device in this moment */
 	if (!S_ISBLK(inode->i_mode)) {
@@ -513,15 +658,13 @@ static ssize_t backing_dev_store(struct device *dev,
 		goto out;
 	}
 
-	bdev_handle = bdev_open_by_dev(inode->i_rdev,
-				BLK_OPEN_READ | BLK_OPEN_WRITE, zram, NULL);
-	if (IS_ERR(bdev_handle)) {
-		err = PTR_ERR(bdev_handle);
-		bdev_handle = NULL;
+	nr_pages = i_size_read(inode) >> PAGE_SHIFT;
+	/* Refuse to use zero sized device (also prevents self reference) */
+	if (!nr_pages) {
+		err = -EINVAL;
 		goto out;
 	}
 
-	nr_pages = i_size_read(inode) >> PAGE_SHIFT;
 	bitmap_sz = BITS_TO_LONGS(nr_pages) * sizeof(long);
 	bitmap = kvzalloc(bitmap_sz, GFP_KERNEL);
 	if (!bitmap) {
@@ -531,7 +674,7 @@ static ssize_t backing_dev_store(struct device *dev,
 
 	reset_bdev(zram);
 
-	zram->bdev_handle = bdev_handle;
+	zram->bdev = I_BDEV(inode);
 	zram->backing_dev = backing_dev;
 	zram->bitmap = bitmap;
 	zram->nr_pages = nr_pages;
@@ -544,9 +687,6 @@ static ssize_t backing_dev_store(struct device *dev,
 out:
 	kvfree(bitmap);
 
-	if (bdev_handle)
-		bdev_release(bdev_handle);
-
 	if (backing_dev)
 		filp_close(backing_dev, NULL);
 
@@ -587,71 +727,28 @@ static void read_from_bdev_async(struct zram *zram, struct page *page,
 {
 	struct bio *bio;
 
-	bio = bio_alloc(zram->bdev_handle->bdev, 1, parent->bi_opf, GFP_NOIO);
+	bio = bio_alloc(zram->bdev, 1, parent->bi_opf, GFP_NOIO);
 	bio->bi_iter.bi_sector = entry * (PAGE_SIZE >> 9);
 	__bio_add_page(bio, page, PAGE_SIZE, 0);
 	bio_chain(bio, parent);
 	submit_bio(bio);
 }
 
-#define PAGE_WB_SIG "page_index="
-
-#define PAGE_WRITEBACK			0
-#define HUGE_WRITEBACK			(1<<0)
-#define IDLE_WRITEBACK			(1<<1)
-#define INCOMPRESSIBLE_WRITEBACK	(1<<2)
-
-static ssize_t writeback_store(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t len)
+static int zram_writeback_slots(struct zram *zram, struct zram_pp_ctl *ctl)
 {
-	struct zram *zram = dev_to_zram(dev);
-	unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
-	unsigned long index = 0;
-	struct bio bio;
-	struct bio_vec bio_vec;
-	struct page *page;
-	ssize_t ret = len;
-	int mode, err;
 	unsigned long blk_idx = 0;
-
-	if (sysfs_streq(buf, "idle"))
-		mode = IDLE_WRITEBACK;
-	else if (sysfs_streq(buf, "huge"))
-		mode = HUGE_WRITEBACK;
-	else if (sysfs_streq(buf, "huge_idle"))
-		mode = IDLE_WRITEBACK | HUGE_WRITEBACK;
-	else if (sysfs_streq(buf, "incompressible"))
-		mode = INCOMPRESSIBLE_WRITEBACK;
-	else {
-		if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1))
-			return -EINVAL;
-
-		if (kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index) ||
-				index >= nr_pages)
-			return -EINVAL;
-
-		nr_pages = 1;
-		mode = PAGE_WRITEBACK;
-	}
-
-	down_read(&zram->init_lock);
-	if (!init_done(zram)) {
-		ret = -EINVAL;
-		goto release_init_lock;
-	}
-
-	if (!zram->backing_dev) {
-		ret = -ENODEV;
-		goto release_init_lock;
-	}
+	struct page *page = NULL;
+	struct zram_pp_slot *pps;
+	struct bio_vec bio_vec;
+	struct bio bio;
+	int ret = 0, err;
+	u32 index;
 
 	page = alloc_page(GFP_KERNEL);
-	if (!page) {
-		ret = -ENOMEM;
-		goto release_init_lock;
-	}
+	if (!page)
+		return -ENOMEM;
 
-	for (; nr_pages != 0; index++, nr_pages--) {
+	while ((pps = select_pp_slot(ctl))) {
 		spin_lock(&zram->wb_limit_lock);
 		if (zram->wb_limit_enable && !zram->bd_wb_limit) {
 			spin_unlock(&zram->wb_limit_lock);
@@ -668,42 +765,21 @@ static ssize_t writeback_store(struct device *dev,
 			}
 		}
 
+		index = pps->index;
 		zram_slot_lock(zram, index);
-		if (!zram_allocated(zram, index))
-			goto next;
-
-		if (zram_test_flag(zram, index, ZRAM_WB) ||
-				zram_test_flag(zram, index, ZRAM_SAME) ||
-				zram_test_flag(zram, index, ZRAM_UNDER_WB))
-			goto next;
-
-		if (mode & IDLE_WRITEBACK &&
-		    !zram_test_flag(zram, index, ZRAM_IDLE))
-			goto next;
-		if (mode & HUGE_WRITEBACK &&
-		    !zram_test_flag(zram, index, ZRAM_HUGE))
-			goto next;
-		if (mode & INCOMPRESSIBLE_WRITEBACK &&
-		    !zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
-			goto next;
-
 		/*
-		 * Clearing ZRAM_UNDER_WB is duty of caller.
-		 * IOW, zram_free_page never clear it.
+		 * scan_slots() sets ZRAM_PP_SLOT and relases slot lock, so
+		 * slots can change in the meantime. If slots are accessed or
+		 * freed they lose ZRAM_PP_SLOT flag and hence we don't
+		 * post-process them.
 		 */
-		zram_set_flag(zram, index, ZRAM_UNDER_WB);
-		/* Need for hugepage writeback racing */
-		zram_set_flag(zram, index, ZRAM_IDLE);
+		if (!zram_test_flag(zram, index, ZRAM_PP_SLOT))
+			goto next;
+		if (zram_read_from_zspool(zram, page, index))
+			goto next;
 		zram_slot_unlock(zram, index);
-		if (zram_read_page(zram, page, index, NULL)) {
-			zram_slot_lock(zram, index);
-			zram_clear_flag(zram, index, ZRAM_UNDER_WB);
-			zram_clear_flag(zram, index, ZRAM_IDLE);
-			zram_slot_unlock(zram, index);
-			continue;
-		}
 
-		bio_init(&bio, zram->bdev_handle->bdev, &bio_vec, 1,
+		bio_init(&bio, zram->bdev, &bio_vec, 1,
 			 REQ_OP_WRITE | REQ_SYNC);
 		bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9);
 		__bio_add_page(&bio, page, PAGE_SIZE, 0);
@@ -714,10 +790,7 @@ static ssize_t writeback_store(struct device *dev,
 		 */
 		err = submit_bio_wait(&bio);
 		if (err) {
-			zram_slot_lock(zram, index);
-			zram_clear_flag(zram, index, ZRAM_UNDER_WB);
-			zram_clear_flag(zram, index, ZRAM_IDLE);
-			zram_slot_unlock(zram, index);
+			release_pp_slot(zram, pps);
 			/*
 			 * BIO errors are not fatal, we continue and simply
 			 * attempt to writeback the remaining objects (pages).
@@ -731,27 +804,21 @@ static ssize_t writeback_store(struct device *dev,
 		}
 
 		atomic64_inc(&zram->stats.bd_writes);
+		zram_slot_lock(zram, index);
 		/*
-		 * We released zram_slot_lock so need to check if the slot was
-		 * changed. If there is freeing for the slot, we can catch it
-		 * easily by zram_allocated.
-		 * A subtle case is the slot is freed/reallocated/marked as
-		 * ZRAM_IDLE again. To close the race, idle_store doesn't
-		 * mark ZRAM_IDLE once it found the slot was ZRAM_UNDER_WB.
-		 * Thus, we could close the race by checking ZRAM_IDLE bit.
+		 * Same as above, we release slot lock during writeback so
+		 * slot can change under us: slot_free() or slot_free() and
+		 * reallocation (zram_write_page()). In both cases slot loses
+		 * ZRAM_PP_SLOT flag. No concurrent post-processing can set
+		 * ZRAM_PP_SLOT on such slots until current post-processing
+		 * finishes.
 		 */
-		zram_slot_lock(zram, index);
-		if (!zram_allocated(zram, index) ||
-			  !zram_test_flag(zram, index, ZRAM_IDLE)) {
-			zram_clear_flag(zram, index, ZRAM_UNDER_WB);
-			zram_clear_flag(zram, index, ZRAM_IDLE);
+		if (!zram_test_flag(zram, index, ZRAM_PP_SLOT))
 			goto next;
-		}
 
 		zram_free_page(zram, index);
-		zram_clear_flag(zram, index, ZRAM_UNDER_WB);
 		zram_set_flag(zram, index, ZRAM_WB);
-		zram_set_element(zram, index, blk_idx);
+		zram_set_handle(zram, index, blk_idx);
 		blk_idx = 0;
 		atomic64_inc(&zram->stats.pages_stored);
 		spin_lock(&zram->wb_limit_lock);
@@ -760,12 +827,224 @@ static ssize_t writeback_store(struct device *dev,
 		spin_unlock(&zram->wb_limit_lock);
 next:
 		zram_slot_unlock(zram, index);
+		release_pp_slot(zram, pps);
+
+		cond_resched();
 	}
 
 	if (blk_idx)
 		free_block_bdev(zram, blk_idx);
-	__free_page(page);
+	if (page)
+		__free_page(page);
+
+	return ret;
+}
+
+#define PAGE_WRITEBACK			0
+#define HUGE_WRITEBACK			(1 << 0)
+#define IDLE_WRITEBACK			(1 << 1)
+#define INCOMPRESSIBLE_WRITEBACK	(1 << 2)
+
+static int parse_page_index(char *val, unsigned long nr_pages,
+			    unsigned long *lo, unsigned long *hi)
+{
+	int ret;
+
+	ret = kstrtoul(val, 10, lo);
+	if (ret)
+		return ret;
+	if (*lo >= nr_pages)
+		return -ERANGE;
+	*hi = *lo + 1;
+	return 0;
+}
+
+static int parse_page_indexes(char *val, unsigned long nr_pages,
+			      unsigned long *lo, unsigned long *hi)
+{
+	char *delim;
+	int ret;
+
+	delim = strchr(val, '-');
+	if (!delim)
+		return -EINVAL;
+
+	*delim = 0x00;
+	ret = kstrtoul(val, 10, lo);
+	if (ret)
+		return ret;
+	if (*lo >= nr_pages)
+		return -ERANGE;
+
+	ret = kstrtoul(delim + 1, 10, hi);
+	if (ret)
+		return ret;
+	if (*hi >= nr_pages || *lo > *hi)
+		return -ERANGE;
+	*hi += 1;
+	return 0;
+}
+
+static int parse_mode(char *val, u32 *mode)
+{
+	*mode = 0;
+
+	if (!strcmp(val, "idle"))
+		*mode = IDLE_WRITEBACK;
+	if (!strcmp(val, "huge"))
+		*mode = HUGE_WRITEBACK;
+	if (!strcmp(val, "huge_idle"))
+		*mode = IDLE_WRITEBACK | HUGE_WRITEBACK;
+	if (!strcmp(val, "incompressible"))
+		*mode = INCOMPRESSIBLE_WRITEBACK;
+
+	if (*mode == 0)
+		return -EINVAL;
+	return 0;
+}
+
+static int scan_slots_for_writeback(struct zram *zram, u32 mode,
+				    unsigned long lo, unsigned long hi,
+				    struct zram_pp_ctl *ctl)
+{
+	u32 index = lo;
+
+	while (index < hi) {
+		bool ok = true;
+
+		zram_slot_lock(zram, index);
+		if (!zram_allocated(zram, index))
+			goto next;
+
+		if (zram_test_flag(zram, index, ZRAM_WB) ||
+		    zram_test_flag(zram, index, ZRAM_SAME))
+			goto next;
+
+		if (mode & IDLE_WRITEBACK &&
+		    !zram_test_flag(zram, index, ZRAM_IDLE))
+			goto next;
+		if (mode & HUGE_WRITEBACK &&
+		    !zram_test_flag(zram, index, ZRAM_HUGE))
+			goto next;
+		if (mode & INCOMPRESSIBLE_WRITEBACK &&
+		    !zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
+			goto next;
+
+		ok = place_pp_slot(zram, ctl, index);
+next:
+		zram_slot_unlock(zram, index);
+		if (!ok)
+			break;
+		index++;
+	}
+
+	return 0;
+}
+
+static ssize_t writeback_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t len)
+{
+	struct zram *zram = dev_to_zram(dev);
+	u64 nr_pages = zram->disksize >> PAGE_SHIFT;
+	unsigned long lo = 0, hi = nr_pages;
+	struct zram_pp_ctl *ctl = NULL;
+	char *args, *param, *val;
+	ssize_t ret = len;
+	int err, mode = 0;
+
+	down_read(&zram->init_lock);
+	if (!init_done(zram)) {
+		up_read(&zram->init_lock);
+		return -EINVAL;
+	}
+
+	/* Do not permit concurrent post-processing actions. */
+	if (atomic_xchg(&zram->pp_in_progress, 1)) {
+		up_read(&zram->init_lock);
+		return -EAGAIN;
+	}
+
+	if (!zram->backing_dev) {
+		ret = -ENODEV;
+		goto release_init_lock;
+	}
+
+	ctl = init_pp_ctl();
+	if (!ctl) {
+		ret = -ENOMEM;
+		goto release_init_lock;
+	}
+
+	args = skip_spaces(buf);
+	while (*args) {
+		args = next_arg(args, &param, &val);
+
+		/*
+		 * Workaround to support the old writeback interface.
+		 *
+		 * The old writeback interface has a minor inconsistency and
+		 * requires key=value only for page_index parameter, while the
+		 * writeback mode is a valueless parameter.
+		 *
+		 * This is not the case anymore and now all parameters are
+		 * required to have values, however, we need to support the
+		 * legacy writeback interface format so we check if we can
+		 * recognize a valueless parameter as the (legacy) writeback
+		 * mode.
+		 */
+		if (!val || !*val) {
+			err = parse_mode(param, &mode);
+			if (err) {
+				ret = err;
+				goto release_init_lock;
+			}
+
+			scan_slots_for_writeback(zram, mode, lo, hi, ctl);
+			break;
+		}
+
+		if (!strcmp(param, "type")) {
+			err = parse_mode(val, &mode);
+			if (err) {
+				ret = err;
+				goto release_init_lock;
+			}
+
+			scan_slots_for_writeback(zram, mode, lo, hi, ctl);
+			break;
+		}
+
+		if (!strcmp(param, "page_index")) {
+			err = parse_page_index(val, nr_pages, &lo, &hi);
+			if (err) {
+				ret = err;
+				goto release_init_lock;
+			}
+
+			scan_slots_for_writeback(zram, mode, lo, hi, ctl);
+			continue;
+		}
+
+		if (!strcmp(param, "page_indexes")) {
+			err = parse_page_indexes(val, nr_pages, &lo, &hi);
+			if (err) {
+				ret = err;
+				goto release_init_lock;
+			}
+
+			scan_slots_for_writeback(zram, mode, lo, hi, ctl);
+			continue;
+		}
+	}
+
+	err = zram_writeback_slots(zram, ctl);
+	if (err)
+		ret = err;
+
 release_init_lock:
+	release_pp_ctl(zram, ctl);
+	atomic_set(&zram->pp_in_progress, 0);
 	up_read(&zram->init_lock);
 
 	return ret;
@@ -785,7 +1064,7 @@ static void zram_sync_read(struct work_struct *work)
 	struct bio_vec bv;
 	struct bio bio;
 
-	bio_init(&bio, zw->zram->bdev_handle->bdev, &bv, 1, REQ_OP_READ);
+	bio_init(&bio, zw->zram->bdev, &bv, 1, REQ_OP_READ);
 	bio.bi_iter.bi_sector = zw->entry * (PAGE_SIZE >> 9);
 	__bio_add_page(&bio, zw->page, PAGE_SIZE, 0);
 	zw->error = submit_bio_wait(&bio);
@@ -937,27 +1216,6 @@ static void zram_debugfs_register(struct zram *zram) {};
 static void zram_debugfs_unregister(struct zram *zram) {};
 #endif
 
-/*
- * We switched to per-cpu streams and this attr is not needed anymore.
- * However, we will keep it around for some time, because:
- * a) we may revert per-cpu streams in the future
- * b) it's visible to user space and we need to follow our 2 years
- *    retirement rule; but we already have a number of 'soon to be
- *    altered' attrs, so max_comp_streams need to wait for the next
- *    layoff cycle.
- */
-static ssize_t max_comp_streams_show(struct device *dev,
-		struct device_attribute *attr, char *buf)
-{
-	return scnprintf(buf, PAGE_SIZE, "%d\n", num_online_cpus());
-}
-
-static ssize_t max_comp_streams_store(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t len)
-{
-	return len;
-}
-
 static void comp_algorithm_set(struct zram *zram, u32 prio, const char *alg)
 {
 	/* Do not free statically defined compression algorithms */
@@ -984,7 +1242,7 @@ static int __comp_algorithm_store(struct zram *zram, u32 prio, const char *buf)
 	size_t sz;
 
 	sz = strlen(buf);
-	if (sz >= CRYPTO_MAX_ALG_NAME)
+	if (sz >= ZRAM_MAX_ALGO_NAME_SZ)
 		return -E2BIG;
 
 	compressor = kstrdup(buf, GFP_KERNEL);
@@ -1013,6 +1271,116 @@ static int __comp_algorithm_store(struct zram *zram, u32 prio, const char *buf)
 	return 0;
 }
 
+static void comp_params_reset(struct zram *zram, u32 prio)
+{
+	struct zcomp_params *params = &zram->params[prio];
+
+	vfree(params->dict);
+	params->level = ZCOMP_PARAM_NOT_SET;
+	params->deflate.winbits = ZCOMP_PARAM_NOT_SET;
+	params->dict_sz = 0;
+	params->dict = NULL;
+}
+
+static int comp_params_store(struct zram *zram, u32 prio, s32 level,
+			     const char *dict_path,
+			     struct deflate_params *deflate_params)
+{
+	ssize_t sz = 0;
+
+	comp_params_reset(zram, prio);
+
+	if (dict_path) {
+		sz = kernel_read_file_from_path(dict_path, 0,
+						&zram->params[prio].dict,
+						INT_MAX,
+						NULL,
+						READING_POLICY);
+		if (sz < 0)
+			return -EINVAL;
+	}
+
+	zram->params[prio].dict_sz = sz;
+	zram->params[prio].level = level;
+	zram->params[prio].deflate.winbits = deflate_params->winbits;
+	return 0;
+}
+
+static ssize_t algorithm_params_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf,
+				      size_t len)
+{
+	s32 prio = ZRAM_PRIMARY_COMP, level = ZCOMP_PARAM_NOT_SET;
+	char *args, *param, *val, *algo = NULL, *dict_path = NULL;
+	struct deflate_params deflate_params;
+	struct zram *zram = dev_to_zram(dev);
+	int ret;
+
+	deflate_params.winbits = ZCOMP_PARAM_NOT_SET;
+
+	args = skip_spaces(buf);
+	while (*args) {
+		args = next_arg(args, &param, &val);
+
+		if (!val || !*val)
+			return -EINVAL;
+
+		if (!strcmp(param, "priority")) {
+			ret = kstrtoint(val, 10, &prio);
+			if (ret)
+				return ret;
+			continue;
+		}
+
+		if (!strcmp(param, "level")) {
+			ret = kstrtoint(val, 10, &level);
+			if (ret)
+				return ret;
+			continue;
+		}
+
+		if (!strcmp(param, "algo")) {
+			algo = val;
+			continue;
+		}
+
+		if (!strcmp(param, "dict")) {
+			dict_path = val;
+			continue;
+		}
+
+		if (!strcmp(param, "deflate.winbits")) {
+			ret = kstrtoint(val, 10, &deflate_params.winbits);
+			if (ret)
+				return ret;
+			continue;
+		}
+	}
+
+	/* Lookup priority by algorithm name */
+	if (algo) {
+		s32 p;
+
+		prio = -EINVAL;
+		for (p = ZRAM_PRIMARY_COMP; p < ZRAM_MAX_COMPS; p++) {
+			if (!zram->comp_algs[p])
+				continue;
+
+			if (!strcmp(zram->comp_algs[p], algo)) {
+				prio = p;
+				break;
+			}
+		}
+	}
+
+	if (prio < ZRAM_PRIMARY_COMP || prio >= ZRAM_MAX_COMPS)
+		return -EINVAL;
+
+	ret = comp_params_store(zram, prio, level, dict_path, &deflate_params);
+	return ret ? ret : len;
+}
+
 static ssize_t comp_algorithm_show(struct device *dev,
 				   struct device_attribute *attr,
 				   char *buf)
@@ -1195,9 +1563,8 @@ static ssize_t debug_stat_show(struct device *dev,
 
 	down_read(&zram->init_lock);
 	ret = scnprintf(buf, PAGE_SIZE,
-			"version: %d\n%8llu %8llu\n",
+			"version: %d\n0 %8llu\n",
 			version,
-			(u64)atomic64_read(&zram->stats.writestall),
 			(u64)atomic64_read(&zram->stats.miss_free));
 	up_read(&zram->init_lock);
 
@@ -1216,17 +1583,21 @@ static void zram_meta_free(struct zram *zram, u64 disksize)
 	size_t num_pages = disksize >> PAGE_SHIFT;
 	size_t index;
 
+	if (!zram->table)
+		return;
+
 	/* Free all pages that are still in this zram device */
 	for (index = 0; index < num_pages; index++)
 		zram_free_page(zram, index);
 
 	zs_destroy_pool(zram->mem_pool);
 	vfree(zram->table);
+	zram->table = NULL;
 }
 
 static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 {
-	size_t num_pages;
+	size_t num_pages, index;
 
 	num_pages = disksize >> PAGE_SHIFT;
 	zram->table = vzalloc(array_size(num_pages, sizeof(*zram->table)));
@@ -1236,19 +1607,19 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 	zram->mem_pool = zs_create_pool(zram->disk->disk_name);
 	if (!zram->mem_pool) {
 		vfree(zram->table);
+		zram->table = NULL;
 		return false;
 	}
 
 	if (!huge_class_size)
 		huge_class_size = zs_huge_class_size(zram->mem_pool);
+
+	for (index = 0; index < num_pages; index++)
+		zram_slot_lock_init(zram, index);
+
 	return true;
 }
 
-/*
- * To protect concurrent access to the same index entry,
- * caller should hold this table index entry's bit_spinlock to
- * indicate this index entry is accessing.
- */
 static void zram_free_page(struct zram *zram, size_t index)
 {
 	unsigned long handle;
@@ -1256,22 +1627,20 @@ static void zram_free_page(struct zram *zram, size_t index)
 #ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
 	zram->table[index].ac_time = 0;
 #endif
-	if (zram_test_flag(zram, index, ZRAM_IDLE))
-		zram_clear_flag(zram, index, ZRAM_IDLE);
+
+	zram_clear_flag(zram, index, ZRAM_IDLE);
+	zram_clear_flag(zram, index, ZRAM_INCOMPRESSIBLE);
+	zram_clear_flag(zram, index, ZRAM_PP_SLOT);
+	zram_set_priority(zram, index, 0);
 
 	if (zram_test_flag(zram, index, ZRAM_HUGE)) {
 		zram_clear_flag(zram, index, ZRAM_HUGE);
 		atomic64_dec(&zram->stats.huge_pages);
 	}
 
-	if (zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
-		zram_clear_flag(zram, index, ZRAM_INCOMPRESSIBLE);
-
-	zram_set_priority(zram, index, 0);
-
 	if (zram_test_flag(zram, index, ZRAM_WB)) {
 		zram_clear_flag(zram, index, ZRAM_WB);
-		free_block_bdev(zram, zram_get_element(zram, index));
+		free_block_bdev(zram, zram_get_handle(zram, index));
 		goto out;
 	}
 
@@ -1292,64 +1661,80 @@ static void zram_free_page(struct zram *zram, size_t index)
 	zs_free(zram->mem_pool, handle);
 
 	atomic64_sub(zram_get_obj_size(zram, index),
-			&zram->stats.compr_data_size);
+		     &zram->stats.compr_data_size);
 out:
 	atomic64_dec(&zram->stats.pages_stored);
 	zram_set_handle(zram, index, 0);
 	zram_set_obj_size(zram, index, 0);
-	WARN_ON_ONCE(zram->table[index].flags &
-		~(1UL << ZRAM_LOCK | 1UL << ZRAM_UNDER_WB));
 }
 
-/*
- * Reads (decompresses if needed) a page from zspool (zsmalloc).
- * Corresponding ZRAM slot should be locked.
- */
-static int zram_read_from_zspool(struct zram *zram, struct page *page,
+static int read_same_filled_page(struct zram *zram, struct page *page,
 				 u32 index)
 {
+	void *mem;
+
+	mem = kmap_local_page(page);
+	zram_fill_page(mem, PAGE_SIZE, zram_get_handle(zram, index));
+	kunmap_local(mem);
+	return 0;
+}
+
+static int read_incompressible_page(struct zram *zram, struct page *page,
+				    u32 index)
+{
+	unsigned long handle;
+	void *src, *dst;
+
+	handle = zram_get_handle(zram, index);
+	src = zs_obj_read_begin(zram->mem_pool, handle, NULL);
+	dst = kmap_local_page(page);
+	copy_page(dst, src);
+	kunmap_local(dst);
+	zs_obj_read_end(zram->mem_pool, handle, src);
+
+	return 0;
+}
+
+static int read_compressed_page(struct zram *zram, struct page *page, u32 index)
+{
 	struct zcomp_strm *zstrm;
 	unsigned long handle;
 	unsigned int size;
 	void *src, *dst;
-	u32 prio;
-	int ret;
+	int ret, prio;
 
 	handle = zram_get_handle(zram, index);
-	if (!handle || zram_test_flag(zram, index, ZRAM_SAME)) {
-		unsigned long value;
-		void *mem;
-
-		value = handle ? zram_get_element(zram, index) : 0;
-		mem = kmap_local_page(page);
-		zram_fill_page(mem, PAGE_SIZE, value);
-		kunmap_local(mem);
-		return 0;
-	}
-
 	size = zram_get_obj_size(zram, index);
+	prio = zram_get_priority(zram, index);
 
-	if (size != PAGE_SIZE) {
-		prio = zram_get_priority(zram, index);
-		zstrm = zcomp_stream_get(zram->comps[prio]);
-	}
+	zstrm = zcomp_stream_get(zram->comps[prio]);
+	src = zs_obj_read_begin(zram->mem_pool, handle, zstrm->local_copy);
+	dst = kmap_local_page(page);
+	ret = zcomp_decompress(zram->comps[prio], zstrm, src, size, dst);
+	kunmap_local(dst);
+	zs_obj_read_end(zram->mem_pool, handle, src);
+	zcomp_stream_put(zstrm);
 
-	src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
-	if (size == PAGE_SIZE) {
-		dst = kmap_local_page(page);
-		memcpy(dst, src, PAGE_SIZE);
-		kunmap_local(dst);
-		ret = 0;
-	} else {
-		dst = kmap_local_page(page);
-		ret = zcomp_decompress(zstrm, src, size, dst);
-		kunmap_local(dst);
-		zcomp_stream_put(zram->comps[prio]);
-	}
-	zs_unmap_object(zram->mem_pool, handle);
 	return ret;
 }
 
+/*
+ * Reads (decompresses if needed) a page from zspool (zsmalloc).
+ * Corresponding ZRAM slot should be locked.
+ */
+static int zram_read_from_zspool(struct zram *zram, struct page *page,
+				 u32 index)
+{
+	if (zram_test_flag(zram, index, ZRAM_SAME) ||
+	    !zram_get_handle(zram, index))
+		return read_same_filled_page(zram, page, index);
+
+	if (!zram_test_flag(zram, index, ZRAM_HUGE))
+		return read_compressed_page(zram, page, index);
+	else
+		return read_incompressible_page(zram, page, index);
+}
+
 static int zram_read_page(struct zram *zram, struct page *page, u32 index,
 			  struct bio *parent)
 {
@@ -1367,7 +1752,7 @@ static int zram_read_page(struct zram *zram, struct page *page, u32 index,
 		 */
 		zram_slot_unlock(zram, index);
 
-		ret = read_from_bdev(zram, page, zram_get_element(zram, index),
+		ret = read_from_bdev(zram, page, zram_get_handle(zram, index),
 				     parent);
 	}
 
@@ -1405,128 +1790,124 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 	return zram_read_page(zram, bvec->bv_page, index, bio);
 }
 
+static int write_same_filled_page(struct zram *zram, unsigned long fill,
+				  u32 index)
+{
+	zram_slot_lock(zram, index);
+	zram_set_flag(zram, index, ZRAM_SAME);
+	zram_set_handle(zram, index, fill);
+	zram_slot_unlock(zram, index);
+
+	atomic64_inc(&zram->stats.same_pages);
+	atomic64_inc(&zram->stats.pages_stored);
+
+	return 0;
+}
+
+static int write_incompressible_page(struct zram *zram, struct page *page,
+				     u32 index)
+{
+	unsigned long handle;
+	void *src;
+
+	/*
+	 * This function is called from preemptible context so we don't need
+	 * to do optimistic and fallback to pessimistic handle allocation,
+	 * like we do for compressible pages.
+	 */
+	handle = zs_malloc(zram->mem_pool, PAGE_SIZE,
+			   GFP_NOIO | __GFP_NOWARN |
+			   __GFP_HIGHMEM | __GFP_MOVABLE, page_to_nid(page));
+	if (IS_ERR_VALUE(handle))
+		return PTR_ERR((void *)handle);
+
+	if (!zram_can_store_page(zram)) {
+		zs_free(zram->mem_pool, handle);
+		return -ENOMEM;
+	}
+
+	src = kmap_local_page(page);
+	zs_obj_write(zram->mem_pool, handle, src, PAGE_SIZE);
+	kunmap_local(src);
+
+	zram_slot_lock(zram, index);
+	zram_set_flag(zram, index, ZRAM_HUGE);
+	zram_set_handle(zram, index, handle);
+	zram_set_obj_size(zram, index, PAGE_SIZE);
+	zram_slot_unlock(zram, index);
+
+	atomic64_add(PAGE_SIZE, &zram->stats.compr_data_size);
+	atomic64_inc(&zram->stats.huge_pages);
+	atomic64_inc(&zram->stats.huge_pages_since);
+	atomic64_inc(&zram->stats.pages_stored);
+
+	return 0;
+}
+
 static int zram_write_page(struct zram *zram, struct page *page, u32 index)
 {
 	int ret = 0;
-	unsigned long alloced_pages;
-	unsigned long handle = -ENOMEM;
-	unsigned int comp_len = 0;
-	void *src, *dst, *mem;
+	unsigned long handle;
+	unsigned int comp_len;
+	void *mem;
 	struct zcomp_strm *zstrm;
-	unsigned long element = 0;
-	enum zram_pageflags flags = 0;
+	unsigned long element;
+	bool same_filled;
+
+	/* First, free memory allocated to this slot (if any) */
+	zram_slot_lock(zram, index);
+	zram_free_page(zram, index);
+	zram_slot_unlock(zram, index);
 
 	mem = kmap_local_page(page);
-	if (page_same_filled(mem, &element)) {
-		kunmap_local(mem);
-		/* Free memory associated with this sector now. */
-		flags = ZRAM_SAME;
-		atomic64_inc(&zram->stats.same_pages);
-		goto out;
-	}
+	same_filled = page_same_filled(mem, &element);
 	kunmap_local(mem);
+	if (same_filled)
+		return write_same_filled_page(zram, element, index);
 
-compress_again:
 	zstrm = zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]);
-	src = kmap_local_page(page);
-	ret = zcomp_compress(zstrm, src, &comp_len);
-	kunmap_local(src);
+	mem = kmap_local_page(page);
+	ret = zcomp_compress(zram->comps[ZRAM_PRIMARY_COMP], zstrm,
+			     mem, &comp_len);
+	kunmap_local(mem);
 
 	if (unlikely(ret)) {
-		zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
+		zcomp_stream_put(zstrm);
 		pr_err("Compression failed! err=%d\n", ret);
-		zs_free(zram->mem_pool, handle);
 		return ret;
 	}
 
-	if (comp_len >= huge_class_size)
-		comp_len = PAGE_SIZE;
-	/*
-	 * handle allocation has 2 paths:
-	 * a) fast path is executed with preemption disabled (for
-	 *  per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
-	 *  since we can't sleep;
-	 * b) slow path enables preemption and attempts to allocate
-	 *  the page with __GFP_DIRECT_RECLAIM bit set. we have to
-	 *  put per-cpu compression stream and, thus, to re-do
-	 *  the compression once handle is allocated.
-	 *
-	 * if we have a 'non-null' handle here then we are coming
-	 * from the slow path and handle has already been allocated.
-	 */
-	if (IS_ERR_VALUE(handle))
-		handle = zs_malloc(zram->mem_pool, comp_len,
-				__GFP_KSWAPD_RECLAIM |
-				__GFP_NOWARN |
-				__GFP_HIGHMEM |
-				__GFP_MOVABLE);
-	if (IS_ERR_VALUE(handle)) {
-		zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
-		atomic64_inc(&zram->stats.writestall);
-		handle = zs_malloc(zram->mem_pool, comp_len,
-				GFP_NOIO | __GFP_HIGHMEM |
-				__GFP_MOVABLE);
-		if (IS_ERR_VALUE(handle))
-			return PTR_ERR((void *)handle);
-
-		if (comp_len != PAGE_SIZE)
-			goto compress_again;
-		/*
-		 * If the page is not compressible, you need to acquire the
-		 * lock and execute the code below. The zcomp_stream_get()
-		 * call is needed to disable the cpu hotplug and grab the
-		 * zstrm buffer back. It is necessary that the dereferencing
-		 * of the zstrm variable below occurs correctly.
-		 */
-		zstrm = zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]);
+	if (comp_len >= huge_class_size) {
+		zcomp_stream_put(zstrm);
+		return write_incompressible_page(zram, page, index);
 	}
 
-	alloced_pages = zs_get_total_pages(zram->mem_pool);
-	update_used_max(zram, alloced_pages);
+	handle = zs_malloc(zram->mem_pool, comp_len,
+			   GFP_NOIO | __GFP_NOWARN |
+			   __GFP_HIGHMEM | __GFP_MOVABLE, page_to_nid(page));
+	if (IS_ERR_VALUE(handle)) {
+		zcomp_stream_put(zstrm);
+		return PTR_ERR((void *)handle);
+	}
 
-	if (zram->limit_pages && alloced_pages > zram->limit_pages) {
-		zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
+	if (!zram_can_store_page(zram)) {
+		zcomp_stream_put(zstrm);
 		zs_free(zram->mem_pool, handle);
 		return -ENOMEM;
 	}
 
-	dst = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
-
-	src = zstrm->buffer;
-	if (comp_len == PAGE_SIZE)
-		src = kmap_local_page(page);
-	memcpy(dst, src, comp_len);
-	if (comp_len == PAGE_SIZE)
-		kunmap_local(src);
+	zs_obj_write(zram->mem_pool, handle, zstrm->buffer, comp_len);
+	zcomp_stream_put(zstrm);
 
-	zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
-	zs_unmap_object(zram->mem_pool, handle);
-	atomic64_add(comp_len, &zram->stats.compr_data_size);
-out:
-	/*
-	 * Free memory associated with this sector
-	 * before overwriting unused sectors.
-	 */
 	zram_slot_lock(zram, index);
-	zram_free_page(zram, index);
-
-	if (comp_len == PAGE_SIZE) {
-		zram_set_flag(zram, index, ZRAM_HUGE);
-		atomic64_inc(&zram->stats.huge_pages);
-		atomic64_inc(&zram->stats.huge_pages_since);
-	}
-
-	if (flags) {
-		zram_set_flag(zram, index, flags);
-		zram_set_element(zram, index, element);
-	}  else {
-		zram_set_handle(zram, index, handle);
-		zram_set_obj_size(zram, index, comp_len);
-	}
+	zram_set_handle(zram, index, handle);
+	zram_set_obj_size(zram, index, comp_len);
 	zram_slot_unlock(zram, index);
 
 	/* Update stats */
 	atomic64_inc(&zram->stats.pages_stored);
+	atomic64_add(comp_len, &zram->stats.compr_data_size);
+
 	return ret;
 }
 
@@ -1560,6 +1941,49 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 }
 
 #ifdef CONFIG_ZRAM_MULTI_COMP
+#define RECOMPRESS_IDLE		(1 << 0)
+#define RECOMPRESS_HUGE		(1 << 1)
+
+static int scan_slots_for_recompress(struct zram *zram, u32 mode, u32 prio_max,
+				     struct zram_pp_ctl *ctl)
+{
+	unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
+	unsigned long index;
+
+	for (index = 0; index < nr_pages; index++) {
+		bool ok = true;
+
+		zram_slot_lock(zram, index);
+		if (!zram_allocated(zram, index))
+			goto next;
+
+		if (mode & RECOMPRESS_IDLE &&
+		    !zram_test_flag(zram, index, ZRAM_IDLE))
+			goto next;
+
+		if (mode & RECOMPRESS_HUGE &&
+		    !zram_test_flag(zram, index, ZRAM_HUGE))
+			goto next;
+
+		if (zram_test_flag(zram, index, ZRAM_WB) ||
+		    zram_test_flag(zram, index, ZRAM_SAME) ||
+		    zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
+			goto next;
+
+		/* Already compressed with same of higher priority */
+		if (zram_get_priority(zram, index) + 1 >= prio_max)
+			goto next;
+
+		ok = place_pp_slot(zram, ctl, index);
+next:
+		zram_slot_unlock(zram, index);
+		if (!ok)
+			break;
+	}
+
+	return 0;
+}
+
 /*
  * This function will decompress (unless it's ZRAM_HUGE) the page and then
  * attempt to compress it using provided compression algorithm priority
@@ -1567,8 +1991,9 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
  *
  * Corresponding ZRAM slot should be locked.
  */
-static int zram_recompress(struct zram *zram, u32 index, struct page *page,
-			   u32 threshold, u32 prio, u32 prio_max)
+static int recompress_slot(struct zram *zram, u32 index, struct page *page,
+			   u64 *num_recomp_pages, u32 threshold, u32 prio,
+			   u32 prio_max)
 {
 	struct zcomp_strm *zstrm = NULL;
 	unsigned long handle_old;
@@ -1577,9 +2002,8 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
 	unsigned int comp_len_new;
 	unsigned int class_index_old;
 	unsigned int class_index_new;
-	u32 num_recomps = 0;
-	void *src, *dst;
-	int ret;
+	void *src;
+	int ret = 0;
 
 	handle_old = zram_get_handle(zram, index);
 	if (!handle_old)
@@ -1596,7 +2020,24 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
 	if (ret)
 		return ret;
 
+	/*
+	 * We touched this entry so mark it as non-IDLE. This makes sure that
+	 * we don't preserve IDLE flag and don't incorrectly pick this entry
+	 * for different post-processing type (e.g. writeback).
+	 */
+	zram_clear_flag(zram, index, ZRAM_IDLE);
+
 	class_index_old = zs_lookup_class_index(zram->mem_pool, comp_len_old);
+
+	prio = max(prio, zram_get_priority(zram, index) + 1);
+	/*
+	 * Recompression slots scan should not select slots that are
+	 * already compressed with a higher priority algorithm, but
+	 * just in case
+	 */
+	if (prio >= prio_max)
+		return 0;
+
 	/*
 	 * Iterate the secondary comp algorithms list (in order of priority)
 	 * and try to recompress the page.
@@ -1605,22 +2046,16 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
 		if (!zram->comps[prio])
 			continue;
 
-		/*
-		 * Skip if the object is already re-compressed with a higher
-		 * priority algorithm (or same algorithm).
-		 */
-		if (prio <= zram_get_priority(zram, index))
-			continue;
-
-		num_recomps++;
 		zstrm = zcomp_stream_get(zram->comps[prio]);
 		src = kmap_local_page(page);
-		ret = zcomp_compress(zstrm, src, &comp_len_new);
+		ret = zcomp_compress(zram->comps[prio], zstrm,
+				     src, &comp_len_new);
 		kunmap_local(src);
 
 		if (ret) {
-			zcomp_stream_put(zram->comps[prio]);
-			return ret;
+			zcomp_stream_put(zstrm);
+			zstrm = NULL;
+			break;
 		}
 
 		class_index_new = zs_lookup_class_index(zram->mem_pool,
@@ -1629,7 +2064,8 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
 		/* Continue until we make progress */
 		if (class_index_new >= class_index_old ||
 		    (threshold && comp_len_new >= threshold)) {
-			zcomp_stream_put(zram->comps[prio]);
+			zcomp_stream_put(zstrm);
+			zstrm = NULL;
 			continue;
 		}
 
@@ -1638,55 +2074,52 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
 	}
 
 	/*
-	 * We did not try to recompress, e.g. when we have only one
-	 * secondary algorithm and the page is already recompressed
-	 * using that algorithm
+	 * Decrement the limit (if set) on pages we can recompress, even
+	 * when current recompression was unsuccessful or did not compress
+	 * the page below the threshold, because we still spent resources
+	 * on it.
 	 */
-	if (!zstrm)
-		return 0;
+	if (*num_recomp_pages)
+		*num_recomp_pages -= 1;
+
+	/* Compression error */
+	if (ret)
+		return ret;
 
-	if (class_index_new >= class_index_old) {
+	if (!zstrm) {
 		/*
 		 * Secondary algorithms failed to re-compress the page
-		 * in a way that would save memory, mark the object as
-		 * incompressible so that we will not try to compress
-		 * it again.
+		 * in a way that would save memory.
 		 *
-		 * We need to make sure that all secondary algorithms have
-		 * failed, so we test if the number of recompressions matches
-		 * the number of active secondary algorithms.
+		 * Mark the object incompressible if the max-priority
+		 * algorithm couldn't re-compress it.
 		 */
-		if (num_recomps == zram->num_active_comps - 1)
-			zram_set_flag(zram, index, ZRAM_INCOMPRESSIBLE);
+		if (prio < zram->num_active_comps)
+			return 0;
+		zram_set_flag(zram, index, ZRAM_INCOMPRESSIBLE);
 		return 0;
 	}
 
-	/* Successful recompression but above threshold */
-	if (threshold && comp_len_new >= threshold)
-		return 0;
-
 	/*
-	 * No direct reclaim (slow path) for handle allocation and no
-	 * re-compression attempt (unlike in zram_write_bvec()) since
-	 * we already have stored that object in zsmalloc. If we cannot
-	 * alloc memory for recompressed object then we bail out and
-	 * simply keep the old (existing) object in zsmalloc.
+	 * We are holding per-CPU stream mutex and entry lock so better
+	 * avoid direct reclaim.  Allocation error is not fatal since
+	 * we still have the old object in the mem_pool.
+	 *
+	 * XXX: technically, the node we really want here is the node that holds
+	 * the original compressed data. But that would require us to modify
+	 * zsmalloc API to return this information. For now, we will make do with
+	 * the node of the page allocated for recompression.
 	 */
 	handle_new = zs_malloc(zram->mem_pool, comp_len_new,
-			       __GFP_KSWAPD_RECLAIM |
-			       __GFP_NOWARN |
-			       __GFP_HIGHMEM |
-			       __GFP_MOVABLE);
+			       GFP_NOIO | __GFP_NOWARN |
+			       __GFP_HIGHMEM | __GFP_MOVABLE, page_to_nid(page));
 	if (IS_ERR_VALUE(handle_new)) {
-		zcomp_stream_put(zram->comps[prio]);
+		zcomp_stream_put(zstrm);
 		return PTR_ERR((void *)handle_new);
 	}
 
-	dst = zs_map_object(zram->mem_pool, handle_new, ZS_MM_WO);
-	memcpy(dst, zstrm->buffer, comp_len_new);
-	zcomp_stream_put(zram->comps[prio]);
-
-	zs_unmap_object(zram->mem_pool, handle_new);
+	zs_obj_write(zram->mem_pool, handle_new, zstrm->buffer, comp_len_new);
+	zcomp_stream_put(zstrm);
 
 	zram_free_page(zram, index);
 	zram_set_handle(zram, index, handle_new);
@@ -1699,22 +2132,23 @@ static int zram_recompress(struct zram *zram, u32 index, struct page *page,
 	return 0;
 }
 
-#define RECOMPRESS_IDLE		(1 << 0)
-#define RECOMPRESS_HUGE		(1 << 1)
-
 static ssize_t recompress_store(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t len)
 {
-	u32 prio = ZRAM_SECONDARY_COMP, prio_max = ZRAM_MAX_COMPS;
 	struct zram *zram = dev_to_zram(dev);
-	unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
 	char *args, *param, *val, *algo = NULL;
+	u64 num_recomp_pages = ULLONG_MAX;
+	struct zram_pp_ctl *ctl = NULL;
+	struct zram_pp_slot *pps;
 	u32 mode = 0, threshold = 0;
-	unsigned long index;
-	struct page *page;
+	u32 prio, prio_max;
+	struct page *page = NULL;
 	ssize_t ret;
 
+	prio = ZRAM_SECONDARY_COMP;
+	prio_max = zram->num_active_comps;
+
 	args = skip_spaces(buf);
 	while (*args) {
 		args = next_arg(args, &param, &val);
@@ -1732,6 +2166,17 @@ static ssize_t recompress_store(struct device *dev,
 			continue;
 		}
 
+		if (!strcmp(param, "max_pages")) {
+			/*
+			 * Limit the number of entries (pages) we attempt to
+			 * recompress.
+			 */
+			ret = kstrtoull(val, 10, &num_recomp_pages);
+			if (ret)
+				return ret;
+			continue;
+		}
+
 		if (!strcmp(param, "threshold")) {
 			/*
 			 * We will re-compress only idle objects equal or
@@ -1747,6 +2192,18 @@ static ssize_t recompress_store(struct device *dev,
 			algo = val;
 			continue;
 		}
+
+		if (!strcmp(param, "priority")) {
+			ret = kstrtouint(val, 10, &prio);
+			if (ret)
+				return ret;
+
+			if (prio == ZRAM_PRIMARY_COMP)
+				prio = ZRAM_SECONDARY_COMP;
+
+			prio_max = prio + 1;
+			continue;
+		}
 	}
 
 	if (threshold >= huge_class_size)
@@ -1758,6 +2215,12 @@ static ssize_t recompress_store(struct device *dev,
 		goto release_init_lock;
 	}
 
+	/* Do not permit concurrent post-processing actions. */
+	if (atomic_xchg(&zram->pp_in_progress, 1)) {
+		up_read(&zram->init_lock);
+		return -EAGAIN;
+	}
+
 	if (algo) {
 		bool found = false;
 
@@ -1766,7 +2229,7 @@ static ssize_t recompress_store(struct device *dev,
 				continue;
 
 			if (!strcmp(zram->comp_algs[prio], algo)) {
-				prio_max = min(prio + 1, ZRAM_MAX_COMPS);
+				prio_max = prio + 1;
 				found = true;
 				break;
 			}
@@ -1778,39 +2241,44 @@ static ssize_t recompress_store(struct device *dev,
 		}
 	}
 
+	prio_max = min(prio_max, (u32)zram->num_active_comps);
+	if (prio >= prio_max) {
+		ret = -EINVAL;
+		goto release_init_lock;
+	}
+
 	page = alloc_page(GFP_KERNEL);
 	if (!page) {
 		ret = -ENOMEM;
 		goto release_init_lock;
 	}
 
-	ret = len;
-	for (index = 0; index < nr_pages; index++) {
-		int err = 0;
-
-		zram_slot_lock(zram, index);
+	ctl = init_pp_ctl();
+	if (!ctl) {
+		ret = -ENOMEM;
+		goto release_init_lock;
+	}
 
-		if (!zram_allocated(zram, index))
-			goto next;
+	scan_slots_for_recompress(zram, mode, prio_max, ctl);
 
-		if (mode & RECOMPRESS_IDLE &&
-		    !zram_test_flag(zram, index, ZRAM_IDLE))
-			goto next;
+	ret = len;
+	while ((pps = select_pp_slot(ctl))) {
+		int err = 0;
 
-		if (mode & RECOMPRESS_HUGE &&
-		    !zram_test_flag(zram, index, ZRAM_HUGE))
-			goto next;
+		if (!num_recomp_pages)
+			break;
 
-		if (zram_test_flag(zram, index, ZRAM_WB) ||
-		    zram_test_flag(zram, index, ZRAM_UNDER_WB) ||
-		    zram_test_flag(zram, index, ZRAM_SAME) ||
-		    zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE))
+		zram_slot_lock(zram, pps->index);
+		if (!zram_test_flag(zram, pps->index, ZRAM_PP_SLOT))
 			goto next;
 
-		err = zram_recompress(zram, index, page, threshold,
+		err = recompress_slot(zram, pps->index, page,
+				      &num_recomp_pages, threshold,
 				      prio, prio_max);
 next:
-		zram_slot_unlock(zram, index);
+		zram_slot_unlock(zram, pps->index);
+		release_pp_slot(zram, pps);
+
 		if (err) {
 			ret = err;
 			break;
@@ -1819,9 +2287,11 @@ next:
 		cond_resched();
 	}
 
-	__free_page(page);
-
 release_init_lock:
+	if (page)
+		__free_page(page);
+	release_pp_ctl(zram, ctl);
+	atomic_set(&zram->pp_in_progress, 0);
 	up_read(&zram->init_lock);
 	return ret;
 }
@@ -1966,11 +2436,20 @@ static void zram_slot_free_notify(struct block_device *bdev,
 	zram_slot_unlock(zram, index);
 }
 
+static void zram_comp_params_reset(struct zram *zram)
+{
+	u32 prio;
+
+	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
+		comp_params_reset(zram, prio);
+	}
+}
+
 static void zram_destroy_comps(struct zram *zram)
 {
 	u32 prio;
 
-	for (prio = 0; prio < ZRAM_MAX_COMPS; prio++) {
+	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
 		struct zcomp *comp = zram->comps[prio];
 
 		zram->comps[prio] = NULL;
@@ -1979,6 +2458,15 @@ static void zram_destroy_comps(struct zram *zram)
 		zcomp_destroy(comp);
 		zram->num_active_comps--;
 	}
+
+	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
+		/* Do not free statically defined compression algorithms */
+		if (zram->comp_algs[prio] != default_compressor)
+			kfree(zram->comp_algs[prio]);
+		zram->comp_algs[prio] = NULL;
+	}
+
+	zram_comp_params_reset(zram);
 }
 
 static void zram_reset_device(struct zram *zram)
@@ -1987,11 +2475,6 @@ static void zram_reset_device(struct zram *zram)
 
 	zram->limit_pages = 0;
 
-	if (!init_done(zram)) {
-		up_write(&zram->init_lock);
-		return;
-	}
-
 	set_capacity_and_notify(zram->disk, 0);
 	part_stat_set_all(zram->disk->part0, 0);
 
@@ -2000,6 +2483,7 @@ static void zram_reset_device(struct zram *zram)
 	zram->disksize = 0;
 	zram_destroy_comps(zram);
 	memset(&zram->stats, 0, sizeof(zram->stats));
+	atomic_set(&zram->pp_in_progress, 0);
 	reset_bdev(zram);
 
 	comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
@@ -2032,11 +2516,12 @@ static ssize_t disksize_store(struct device *dev,
 		goto out_unlock;
 	}
 
-	for (prio = 0; prio < ZRAM_MAX_COMPS; prio++) {
+	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
 		if (!zram->comp_algs[prio])
 			continue;
 
-		comp = zcomp_create(zram->comp_algs[prio]);
+		comp = zcomp_create(zram->comp_algs[prio],
+				    &zram->params[prio]);
 		if (IS_ERR(comp)) {
 			pr_err("Cannot initialise %s compressing backend\n",
 			       zram->comp_algs[prio]);
@@ -2127,7 +2612,6 @@ static DEVICE_ATTR_WO(reset);
 static DEVICE_ATTR_WO(mem_limit);
 static DEVICE_ATTR_WO(mem_used_max);
 static DEVICE_ATTR_WO(idle);
-static DEVICE_ATTR_RW(max_comp_streams);
 static DEVICE_ATTR_RW(comp_algorithm);
 #ifdef CONFIG_ZRAM_WRITEBACK
 static DEVICE_ATTR_RW(backing_dev);
@@ -2139,6 +2623,7 @@ static DEVICE_ATTR_RW(writeback_limit_enable);
 static DEVICE_ATTR_RW(recomp_algorithm);
 static DEVICE_ATTR_WO(recompress);
 #endif
+static DEVICE_ATTR_WO(algorithm_params);
 
 static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_disksize.attr,
@@ -2148,7 +2633,6 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_mem_limit.attr,
 	&dev_attr_mem_used_max.attr,
 	&dev_attr_idle.attr,
-	&dev_attr_max_comp_streams.attr,
 	&dev_attr_comp_algorithm.attr,
 #ifdef CONFIG_ZRAM_WRITEBACK
 	&dev_attr_backing_dev.attr,
@@ -2166,6 +2650,7 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_recomp_algorithm.attr,
 	&dev_attr_recompress.attr,
 #endif
+	&dev_attr_algorithm_params.attr,
 	NULL,
 };
 
@@ -2177,6 +2662,30 @@ ATTRIBUTE_GROUPS(zram_disk);
  */
 static int zram_add(void)
 {
+	struct queue_limits lim = {
+		.logical_block_size		= ZRAM_LOGICAL_BLOCK_SIZE,
+		/*
+		 * To ensure that we always get PAGE_SIZE aligned and
+		 * n*PAGE_SIZED sized I/O requests.
+		 */
+		.physical_block_size		= PAGE_SIZE,
+		.io_min				= PAGE_SIZE,
+		.io_opt				= PAGE_SIZE,
+		.max_hw_discard_sectors		= UINT_MAX,
+		/*
+		 * zram_bio_discard() will clear all logical blocks if logical
+		 * block size is identical with physical block size(PAGE_SIZE).
+		 * But if it is different, we will skip discarding some parts of
+		 * logical blocks in the part of the request range which isn't
+		 * aligned to physical block size.  So we can't ensure that all
+		 * discarded logical blocks are zeroed.
+		 */
+#if ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE
+		.max_write_zeroes_sectors	= UINT_MAX,
+#endif
+		.features			= BLK_FEAT_STABLE_WRITES |
+						  BLK_FEAT_SYNCHRONOUS,
+	};
 	struct zram *zram;
 	int ret, device_id;
 
@@ -2195,11 +2704,11 @@ static int zram_add(void)
 #endif
 
 	/* gendisk structure */
-	zram->disk = blk_alloc_disk(NUMA_NO_NODE);
-	if (!zram->disk) {
+	zram->disk = blk_alloc_disk(&lim, NUMA_NO_NODE);
+	if (IS_ERR(zram->disk)) {
 		pr_err("Error allocating disk structure for device %d\n",
 			device_id);
-		ret = -ENOMEM;
+		ret = PTR_ERR(zram->disk);
 		goto out_free_idr;
 	}
 
@@ -2210,42 +2719,16 @@ static int zram_add(void)
 	zram->disk->fops = &zram_devops;
 	zram->disk->private_data = zram;
 	snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
+	atomic_set(&zram->pp_in_progress, 0);
+	zram_comp_params_reset(zram);
+	comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
 
 	/* Actual capacity set using sysfs (/sys/block/zram<id>/disksize */
 	set_capacity(zram->disk, 0);
-	/* zram devices sort of resembles non-rotational disks */
-	blk_queue_flag_set(QUEUE_FLAG_NONROT, zram->disk->queue);
-	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, zram->disk->queue);
-
-	/*
-	 * To ensure that we always get PAGE_SIZE aligned
-	 * and n*PAGE_SIZED sized I/O requests.
-	 */
-	blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
-	blk_queue_logical_block_size(zram->disk->queue,
-					ZRAM_LOGICAL_BLOCK_SIZE);
-	blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
-	blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
-	blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
-
-	/*
-	 * zram_bio_discard() will clear all logical blocks if logical block
-	 * size is identical with physical block size(PAGE_SIZE). But if it is
-	 * different, we will skip discarding some parts of logical blocks in
-	 * the part of the request range which isn't aligned to physical block
-	 * size.  So we can't ensure that all discarded logical blocks are
-	 * zeroed.
-	 */
-	if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
-		blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX);
-
-	blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, zram->disk->queue);
 	ret = device_add_disk(NULL, zram->disk, zram_disk_groups);
 	if (ret)
 		goto out_cleanup_disk;
 
-	comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
-
 	zram_debugfs_register(zram);
 	pr_info("Added device: %s\n", zram->disk->disk_name);
 	return device_id;
@@ -2394,9 +2877,10 @@ static void destroy_devices(void)
 
 static int __init zram_init(void)
 {
+	struct zram_table_entry zram_te;
 	int ret;
 
-	BUILD_BUG_ON(__NR_ZRAM_PAGEFLAGS > BITS_PER_LONG);
+	BUILD_BUG_ON(__NR_ZRAM_PAGEFLAGS > sizeof(zram_te.flags) * 8);
 
 	ret = cpuhp_setup_state_multi(CPUHP_ZCOMP_PREPARE, "block/zram:prepare",
 				      zcomp_cpu_up_prepare, zcomp_cpu_dead);