Merge branch 'akpm' (patches from Andrew)

Merge updates from Andrew Morton:

 - various misc bits

 - DAX updates

 - OCFS2

 - most of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (119 commits)
  mm,fork: introduce MADV_WIPEONFORK
  x86,mpx: make mpx depend on x86-64 to free up VMA flag
  mm: add /proc/pid/smaps_rollup
  mm: hugetlb: clear target sub-page last when clearing huge page
  mm: oom: let oom_reap_task and exit_mmap run concurrently
  swap: choose swap device according to numa node
  mm: replace TIF_MEMDIE checks by tsk_is_oom_victim
  mm, oom: do not rely on TIF_MEMDIE for memory reserves access
  z3fold: use per-cpu unbuddied lists
  mm, swap: don't use VMA based swap readahead if HDD is used as swap
  mm, swap: add sysfs interface for VMA based swap readahead
  mm, swap: VMA based swap readahead
  mm, swap: fix swap readahead marking
  mm, swap: add swap readahead hit statistics
  mm/vmalloc.c: don't reinvent the wheel but use existing llist API
  mm/vmstat.c: fix wrong comment
  selftests/memfd: add memfd_create hugetlbfs selftest
  mm/shmem: add hugetlbfs support to memfd_create()
  mm, devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups
  mm/vmalloc.c: halve the number of comparisons performed in pcpu_get_vm_areas()
  ...

12 files changed, 563 insertions, 116 deletions

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index c7c4e0325cdb..4e3b61cda520 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -388,6 +388,19 @@ static ssize_t show_phys_device(struct device *dev,
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
+static void print_allowed_zone(char *buf, int nid, unsigned long start_pfn,
+		unsigned long nr_pages, int online_type,
+		struct zone *default_zone)
+{
+	struct zone *zone;
+
+	zone = zone_for_pfn_range(online_type, nid, start_pfn, nr_pages);
+	if (zone != default_zone) {
+		strcat(buf, " ");
+		strcat(buf, zone->name);
+	}
+}
+
 static ssize_t show_valid_zones(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
@@ -395,7 +408,7 @@ static ssize_t show_valid_zones(struct device *dev,
 	unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
 	unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
 	unsigned long valid_start_pfn, valid_end_pfn;
-	bool append = false;
+	struct zone *default_zone;
 	int nid;
 
 	/*
@@ -418,16 +431,13 @@ static ssize_t show_valid_zones(struct device *dev,
 	}
 
 	nid = pfn_to_nid(start_pfn);
-	if (allow_online_pfn_range(nid, start_pfn, nr_pages, MMOP_ONLINE_KERNEL)) {
-		strcat(buf, default_zone_for_pfn(nid, start_pfn, nr_pages)->name);
-		append = true;
-	}
+	default_zone = zone_for_pfn_range(MMOP_ONLINE_KEEP, nid, start_pfn, nr_pages);
+	strcat(buf, default_zone->name);
 
-	if (allow_online_pfn_range(nid, start_pfn, nr_pages, MMOP_ONLINE_MOVABLE)) {
-		if (append)
-			strcat(buf, " ");
-		strcat(buf, NODE_DATA(nid)->node_zones[ZONE_MOVABLE].name);
-	}
+	print_allowed_zone(buf, nid, start_pfn, nr_pages, MMOP_ONLINE_KERNEL,
+			default_zone);
+	print_allowed_zone(buf, nid, start_pfn, nr_pages, MMOP_ONLINE_MOVABLE,
+			default_zone);
 out:
 	strcat(buf, "\n");
 
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 104b71c0490d..5d9ed0616413 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -326,7 +326,11 @@ static int brd_rw_page(struct block_device *bdev, sector_t sector,
 		       struct page *page, bool is_write)
 {
 	struct brd_device *brd = bdev->bd_disk->private_data;
-	int err = brd_do_bvec(brd, page, PAGE_SIZE, 0, is_write, sector);
+	int err;
+
+	if (PageTransHuge(page))
+		return -ENOTSUPP;
+	err = brd_do_bvec(brd, page, PAGE_SIZE, 0, is_write, sector);
 	page_endio(page, is_write, err);
 	return err;
 }
diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index b8ecba6dcd3b..7cd4a8ec3c8f 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -13,3 +13,15 @@ config ZRAM
 	  disks and maybe many more.
 
 	  See zram.txt for more information.
+
+config ZRAM_WRITEBACK
+       bool "Write back incompressible page to backing device"
+       depends on ZRAM
+       default n
+       help
+	 With incompressible page, there is no memory saving to keep it
+	 in memory. Instead, write it out to backing device.
+	 For this feature, admin should set up backing device via
+	 /sys/block/zramX/backing_dev.
+
+	 See zram.txt for more infomration.
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 3b1b6340ba13..4a0438c4ef2a 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -270,6 +270,349 @@ static ssize_t mem_used_max_store(struct device *dev,
 	return len;
 }
 
+#ifdef CONFIG_ZRAM_WRITEBACK
+static bool zram_wb_enabled(struct zram *zram)
+{
+	return zram->backing_dev;
+}
+
+static void reset_bdev(struct zram *zram)
+{
+	struct block_device *bdev;
+
+	if (!zram_wb_enabled(zram))
+		return;
+
+	bdev = zram->bdev;
+	if (zram->old_block_size)
+		set_blocksize(bdev, zram->old_block_size);
+	blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+	/* hope filp_close flush all of IO */
+	filp_close(zram->backing_dev, NULL);
+	zram->backing_dev = NULL;
+	zram->old_block_size = 0;
+	zram->bdev = NULL;
+
+	kvfree(zram->bitmap);
+	zram->bitmap = NULL;
+}
+
+static ssize_t backing_dev_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct zram *zram = dev_to_zram(dev);
+	struct file *file = zram->backing_dev;
+	char *p;
+	ssize_t ret;
+
+	down_read(&zram->init_lock);
+	if (!zram_wb_enabled(zram)) {
+		memcpy(buf, "none\n", 5);
+		up_read(&zram->init_lock);
+		return 5;
+	}
+
+	p = file_path(file, buf, PAGE_SIZE - 1);
+	if (IS_ERR(p)) {
+		ret = PTR_ERR(p);
+		goto out;
+	}
+
+	ret = strlen(p);
+	memmove(buf, p, ret);
+	buf[ret++] = '\n';
+out:
+	up_read(&zram->init_lock);
+	return ret;
+}
+
+static ssize_t backing_dev_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	char *file_name;
+	struct file *backing_dev = NULL;
+	struct inode *inode;
+	struct address_space *mapping;
+	unsigned int bitmap_sz, old_block_size = 0;
+	unsigned long nr_pages, *bitmap = NULL;
+	struct block_device *bdev = NULL;
+	int err;
+	struct zram *zram = dev_to_zram(dev);
+
+	file_name = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!file_name)
+		return -ENOMEM;
+
+	down_write(&zram->init_lock);
+	if (init_done(zram)) {
+		pr_info("Can't setup backing device for initialized device\n");
+		err = -EBUSY;
+		goto out;
+	}
+
+	strlcpy(file_name, buf, len);
+
+	backing_dev = filp_open(file_name, O_RDWR|O_LARGEFILE, 0);
+	if (IS_ERR(backing_dev)) {
+		err = PTR_ERR(backing_dev);
+		backing_dev = NULL;
+		goto out;
+	}
+
+	mapping = backing_dev->f_mapping;
+	inode = mapping->host;
+
+	/* Support only block device in this moment */
+	if (!S_ISBLK(inode->i_mode)) {
+		err = -ENOTBLK;
+		goto out;
+	}
+
+	bdev = bdgrab(I_BDEV(inode));
+	err = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram);
+	if (err < 0)
+		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) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	old_block_size = block_size(bdev);
+	err = set_blocksize(bdev, PAGE_SIZE);
+	if (err)
+		goto out;
+
+	reset_bdev(zram);
+	spin_lock_init(&zram->bitmap_lock);
+
+	zram->old_block_size = old_block_size;
+	zram->bdev = bdev;
+	zram->backing_dev = backing_dev;
+	zram->bitmap = bitmap;
+	zram->nr_pages = nr_pages;
+	up_write(&zram->init_lock);
+
+	pr_info("setup backing device %s\n", file_name);
+	kfree(file_name);
+
+	return len;
+out:
+	if (bitmap)
+		kvfree(bitmap);
+
+	if (bdev)
+		blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
+
+	if (backing_dev)
+		filp_close(backing_dev, NULL);
+
+	up_write(&zram->init_lock);
+
+	kfree(file_name);
+
+	return err;
+}
+
+static unsigned long get_entry_bdev(struct zram *zram)
+{
+	unsigned long entry;
+
+	spin_lock(&zram->bitmap_lock);
+	/* skip 0 bit to confuse zram.handle = 0 */
+	entry = find_next_zero_bit(zram->bitmap, zram->nr_pages, 1);
+	if (entry == zram->nr_pages) {
+		spin_unlock(&zram->bitmap_lock);
+		return 0;
+	}
+
+	set_bit(entry, zram->bitmap);
+	spin_unlock(&zram->bitmap_lock);
+
+	return entry;
+}
+
+static void put_entry_bdev(struct zram *zram, unsigned long entry)
+{
+	int was_set;
+
+	spin_lock(&zram->bitmap_lock);
+	was_set = test_and_clear_bit(entry, zram->bitmap);
+	spin_unlock(&zram->bitmap_lock);
+	WARN_ON_ONCE(!was_set);
+}
+
+void zram_page_end_io(struct bio *bio)
+{
+	struct page *page = bio->bi_io_vec[0].bv_page;
+
+	page_endio(page, op_is_write(bio_op(bio)),
+			blk_status_to_errno(bio->bi_status));
+	bio_put(bio);
+}
+
+/*
+ * Returns 1 if the submission is successful.
+ */
+static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
+			unsigned long entry, struct bio *parent)
+{
+	struct bio *bio;
+
+	bio = bio_alloc(GFP_ATOMIC, 1);
+	if (!bio)
+		return -ENOMEM;
+
+	bio->bi_iter.bi_sector = entry * (PAGE_SIZE >> 9);
+	bio->bi_bdev = zram->bdev;
+	if (!bio_add_page(bio, bvec->bv_page, bvec->bv_len, bvec->bv_offset)) {
+		bio_put(bio);
+		return -EIO;
+	}
+
+	if (!parent) {
+		bio->bi_opf = REQ_OP_READ;
+		bio->bi_end_io = zram_page_end_io;
+	} else {
+		bio->bi_opf = parent->bi_opf;
+		bio_chain(bio, parent);
+	}
+
+	submit_bio(bio);
+	return 1;
+}
+
+struct zram_work {
+	struct work_struct work;
+	struct zram *zram;
+	unsigned long entry;
+	struct bio *bio;
+};
+
+#if PAGE_SIZE != 4096
+static void zram_sync_read(struct work_struct *work)
+{
+	struct bio_vec bvec;
+	struct zram_work *zw = container_of(work, struct zram_work, work);
+	struct zram *zram = zw->zram;
+	unsigned long entry = zw->entry;
+	struct bio *bio = zw->bio;
+
+	read_from_bdev_async(zram, &bvec, entry, bio);
+}
+
+/*
+ * Block layer want one ->make_request_fn to be active at a time
+ * so if we use chained IO with parent IO in same context,
+ * it's a deadlock. To avoid, it, it uses worker thread context.
+ */
+static int read_from_bdev_sync(struct zram *zram, struct bio_vec *bvec,
+				unsigned long entry, struct bio *bio)
+{
+	struct zram_work work;
+
+	work.zram = zram;
+	work.entry = entry;
+	work.bio = bio;
+
+	INIT_WORK_ONSTACK(&work.work, zram_sync_read);
+	queue_work(system_unbound_wq, &work.work);
+	flush_work(&work.work);
+	destroy_work_on_stack(&work.work);
+
+	return 1;
+}
+#else
+static int read_from_bdev_sync(struct zram *zram, struct bio_vec *bvec,
+				unsigned long entry, struct bio *bio)
+{
+	WARN_ON(1);
+	return -EIO;
+}
+#endif
+
+static int read_from_bdev(struct zram *zram, struct bio_vec *bvec,
+			unsigned long entry, struct bio *parent, bool sync)
+{
+	if (sync)
+		return read_from_bdev_sync(zram, bvec, entry, parent);
+	else
+		return read_from_bdev_async(zram, bvec, entry, parent);
+}
+
+static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
+					u32 index, struct bio *parent,
+					unsigned long *pentry)
+{
+	struct bio *bio;
+	unsigned long entry;
+
+	bio = bio_alloc(GFP_ATOMIC, 1);
+	if (!bio)
+		return -ENOMEM;
+
+	entry = get_entry_bdev(zram);
+	if (!entry) {
+		bio_put(bio);
+		return -ENOSPC;
+	}
+
+	bio->bi_iter.bi_sector = entry * (PAGE_SIZE >> 9);
+	bio->bi_bdev = zram->bdev;
+	if (!bio_add_page(bio, bvec->bv_page, bvec->bv_len,
+					bvec->bv_offset)) {
+		bio_put(bio);
+		put_entry_bdev(zram, entry);
+		return -EIO;
+	}
+
+	if (!parent) {
+		bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
+		bio->bi_end_io = zram_page_end_io;
+	} else {
+		bio->bi_opf = parent->bi_opf;
+		bio_chain(bio, parent);
+	}
+
+	submit_bio(bio);
+	*pentry = entry;
+
+	return 0;
+}
+
+static void zram_wb_clear(struct zram *zram, u32 index)
+{
+	unsigned long entry;
+
+	zram_clear_flag(zram, index, ZRAM_WB);
+	entry = zram_get_element(zram, index);
+	zram_set_element(zram, index, 0);
+	put_entry_bdev(zram, entry);
+}
+
+#else
+static bool zram_wb_enabled(struct zram *zram) { return false; }
+static inline void reset_bdev(struct zram *zram) {};
+static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
+					u32 index, struct bio *parent,
+					unsigned long *pentry)
+
+{
+	return -EIO;
+}
+
+static int read_from_bdev(struct zram *zram, struct bio_vec *bvec,
+			unsigned long entry, struct bio *parent, bool sync)
+{
+	return -EIO;
+}
+static void zram_wb_clear(struct zram *zram, u32 index) {}
+#endif
+
+
 /*
  * We switched to per-cpu streams and this attr is not needed anymore.
  * However, we will keep it around for some time, because:
@@ -453,30 +796,6 @@ static bool zram_same_page_read(struct zram *zram, u32 index,
 	return false;
 }
 
-static bool zram_same_page_write(struct zram *zram, u32 index,
-					struct page *page)
-{
-	unsigned long element;
-	void *mem = kmap_atomic(page);
-
-	if (page_same_filled(mem, &element)) {
-		kunmap_atomic(mem);
-		/* Free memory associated with this sector now. */
-		zram_slot_lock(zram, index);
-		zram_free_page(zram, index);
-		zram_set_flag(zram, index, ZRAM_SAME);
-		zram_set_element(zram, index, element);
-		zram_slot_unlock(zram, index);
-
-		atomic64_inc(&zram->stats.same_pages);
-		atomic64_inc(&zram->stats.pages_stored);
-		return true;
-	}
-	kunmap_atomic(mem);
-
-	return false;
-}
-
 static void zram_meta_free(struct zram *zram, u64 disksize)
 {
 	size_t num_pages = disksize >> PAGE_SHIFT;
@@ -515,7 +834,13 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
  */
 static void zram_free_page(struct zram *zram, size_t index)
 {
-	unsigned long handle = zram_get_handle(zram, index);
+	unsigned long handle;
+
+	if (zram_wb_enabled(zram) && zram_test_flag(zram, index, ZRAM_WB)) {
+		zram_wb_clear(zram, index);
+		atomic64_dec(&zram->stats.pages_stored);
+		return;
+	}
 
 	/*
 	 * No memory is allocated for same element filled pages.
@@ -529,6 +854,7 @@ static void zram_free_page(struct zram *zram, size_t index)
 		return;
 	}
 
+	handle = zram_get_handle(zram, index);
 	if (!handle)
 		return;
 
@@ -542,13 +868,31 @@ static void zram_free_page(struct zram *zram, size_t index)
 	zram_set_obj_size(zram, index, 0);
 }
 
-static int zram_decompress_page(struct zram *zram, struct page *page, u32 index)
+static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
+				struct bio *bio, bool partial_io)
 {
 	int ret;
 	unsigned long handle;
 	unsigned int size;
 	void *src, *dst;
 
+	if (zram_wb_enabled(zram)) {
+		zram_slot_lock(zram, index);
+		if (zram_test_flag(zram, index, ZRAM_WB)) {
+			struct bio_vec bvec;
+
+			zram_slot_unlock(zram, index);
+
+			bvec.bv_page = page;
+			bvec.bv_len = PAGE_SIZE;
+			bvec.bv_offset = 0;
+			return read_from_bdev(zram, &bvec,
+					zram_get_element(zram, index),
+					bio, partial_io);
+		}
+		zram_slot_unlock(zram, index);
+	}
+
 	if (zram_same_page_read(zram, index, page, 0, PAGE_SIZE))
 		return 0;
 
@@ -581,7 +925,7 @@ static int zram_decompress_page(struct zram *zram, struct page *page, u32 index)
 }
 
 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
-				u32 index, int offset)
+				u32 index, int offset, struct bio *bio)
 {
 	int ret;
 	struct page *page;
@@ -594,7 +938,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 			return -ENOMEM;
 	}
 
-	ret = zram_decompress_page(zram, page, index);
+	ret = __zram_bvec_read(zram, page, index, bio, is_partial_io(bvec));
 	if (unlikely(ret))
 		goto out;
 
@@ -613,30 +957,57 @@ out:
 	return ret;
 }
 
-static int zram_compress(struct zram *zram, struct zcomp_strm **zstrm,
-			struct page *page,
-			unsigned long *out_handle, unsigned int *out_comp_len)
+static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
+				u32 index, struct bio *bio)
 {
-	int ret;
-	unsigned int comp_len;
-	void *src;
+	int ret = 0;
 	unsigned long alloced_pages;
 	unsigned long handle = 0;
+	unsigned int comp_len = 0;
+	void *src, *dst, *mem;
+	struct zcomp_strm *zstrm;
+	struct page *page = bvec->bv_page;
+	unsigned long element = 0;
+	enum zram_pageflags flags = 0;
+	bool allow_wb = true;
+
+	mem = kmap_atomic(page);
+	if (page_same_filled(mem, &element)) {
+		kunmap_atomic(mem);
+		/* Free memory associated with this sector now. */
+		flags = ZRAM_SAME;
+		atomic64_inc(&zram->stats.same_pages);
+		goto out;
+	}
+	kunmap_atomic(mem);
 
 compress_again:
+	zstrm = zcomp_stream_get(zram->comp);
 	src = kmap_atomic(page);
-	ret = zcomp_compress(*zstrm, src, &comp_len);
+	ret = zcomp_compress(zstrm, src, &comp_len);
 	kunmap_atomic(src);
 
 	if (unlikely(ret)) {
+		zcomp_stream_put(zram->comp);
 		pr_err("Compression failed! err=%d\n", ret);
-		if (handle)
-			zs_free(zram->mem_pool, handle);
+		zs_free(zram->mem_pool, handle);
 		return ret;
 	}
 
-	if (unlikely(comp_len > max_zpage_size))
+	if (unlikely(comp_len > max_zpage_size)) {
+		if (zram_wb_enabled(zram) && allow_wb) {
+			zcomp_stream_put(zram->comp);
+			ret = write_to_bdev(zram, bvec, index, bio, &element);
+			if (!ret) {
+				flags = ZRAM_WB;
+				ret = 1;
+				goto out;
+			}
+			allow_wb = false;
+			goto compress_again;
+		}
 		comp_len = PAGE_SIZE;
+	}
 
 	/*
 	 * handle allocation has 2 paths:
@@ -663,7 +1034,6 @@ compress_again:
 		handle = zs_malloc(zram->mem_pool, comp_len,
 				GFP_NOIO | __GFP_HIGHMEM |
 				__GFP_MOVABLE);
-		*zstrm = zcomp_stream_get(zram->comp);
 		if (handle)
 			goto compress_again;
 		return -ENOMEM;
@@ -673,34 +1043,11 @@ compress_again:
 	update_used_max(zram, alloced_pages);
 
 	if (zram->limit_pages && alloced_pages > zram->limit_pages) {
+		zcomp_stream_put(zram->comp);
 		zs_free(zram->mem_pool, handle);
 		return -ENOMEM;
 	}
 
-	*out_handle = handle;
-	*out_comp_len = comp_len;
-	return 0;
-}
-
-static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
-{
-	int ret;
-	unsigned long handle;
-	unsigned int comp_len;
-	void *src, *dst;
-	struct zcomp_strm *zstrm;
-	struct page *page = bvec->bv_page;
-
-	if (zram_same_page_write(zram, index, page))
-		return 0;
-
-	zstrm = zcomp_stream_get(zram->comp);
-	ret = zram_compress(zram, &zstrm, page, &handle, &comp_len);
-	if (ret) {
-		zcomp_stream_put(zram->comp);
-		return ret;
-	}
-
 	dst = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
 
 	src = zstrm->buffer;
@@ -712,25 +1059,31 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
 
 	zcomp_stream_put(zram->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);
-	zram_set_handle(zram, index, handle);
-	zram_set_obj_size(zram, index, comp_len);
+
+	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_slot_unlock(zram, index);
 
 	/* Update stats */
-	atomic64_add(comp_len, &zram->stats.compr_data_size);
 	atomic64_inc(&zram->stats.pages_stored);
-	return 0;
+	return ret;
 }
 
 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
-				u32 index, int offset)
+				u32 index, int offset, struct bio *bio)
 {
 	int ret;
 	struct page *page = NULL;
@@ -748,7 +1101,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 		if (!page)
 			return -ENOMEM;
 
-		ret = zram_decompress_page(zram, page, index);
+		ret = __zram_bvec_read(zram, page, index, bio, true);
 		if (ret)
 			goto out;
 
@@ -763,7 +1116,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 		vec.bv_offset = 0;
 	}
 
-	ret = __zram_bvec_write(zram, &vec, index);
+	ret = __zram_bvec_write(zram, &vec, index, bio);
 out:
 	if (is_partial_io(bvec))
 		__free_page(page);
@@ -808,8 +1161,13 @@ static void zram_bio_discard(struct zram *zram, u32 index,
 	}
 }
 
+/*
+ * Returns errno if it has some problem. Otherwise return 0 or 1.
+ * Returns 0 if IO request was done synchronously
+ * Returns 1 if IO request was successfully submitted.
+ */
 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
-			int offset, bool is_write)
+			int offset, bool is_write, struct bio *bio)
 {
 	unsigned long start_time = jiffies;
 	int rw_acct = is_write ? REQ_OP_WRITE : REQ_OP_READ;
@@ -820,16 +1178,16 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	if (!is_write) {
 		atomic64_inc(&zram->stats.num_reads);
-		ret = zram_bvec_read(zram, bvec, index, offset);
+		ret = zram_bvec_read(zram, bvec, index, offset, bio);
 		flush_dcache_page(bvec->bv_page);
 	} else {
 		atomic64_inc(&zram->stats.num_writes);
-		ret = zram_bvec_write(zram, bvec, index, offset);
+		ret = zram_bvec_write(zram, bvec, index, offset, bio);
 	}
 
 	generic_end_io_acct(rw_acct, &zram->disk->part0, start_time);
 
-	if (unlikely(ret)) {
+	if (unlikely(ret < 0)) {
 		if (!is_write)
 			atomic64_inc(&zram->stats.failed_reads);
 		else
@@ -868,7 +1226,7 @@ static void __zram_make_request(struct zram *zram, struct bio *bio)
 			bv.bv_len = min_t(unsigned int, PAGE_SIZE - offset,
 							unwritten);
 			if (zram_bvec_rw(zram, &bv, index, offset,
-					op_is_write(bio_op(bio))) < 0)
+					op_is_write(bio_op(bio)), bio) < 0)
 				goto out;
 
 			bv.bv_offset += bv.bv_len;
@@ -922,16 +1280,18 @@ static void zram_slot_free_notify(struct block_device *bdev,
 static int zram_rw_page(struct block_device *bdev, sector_t sector,
 		       struct page *page, bool is_write)
 {
-	int offset, err = -EIO;
+	int offset, ret;
 	u32 index;
 	struct zram *zram;
 	struct bio_vec bv;
 
+	if (PageTransHuge(page))
+		return -ENOTSUPP;
 	zram = bdev->bd_disk->private_data;
 
 	if (!valid_io_request(zram, sector, PAGE_SIZE)) {
 		atomic64_inc(&zram->stats.invalid_io);
-		err = -EINVAL;
+		ret = -EINVAL;
 		goto out;
 	}
 
@@ -942,7 +1302,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
 	bv.bv_len = PAGE_SIZE;
 	bv.bv_offset = 0;
 
-	err = zram_bvec_rw(zram, &bv, index, offset, is_write);
+	ret = zram_bvec_rw(zram, &bv, index, offset, is_write, NULL);
 out:
 	/*
 	 * If I/O fails, just return error(ie, non-zero) without
@@ -952,9 +1312,20 @@ out:
 	 * bio->bi_end_io does things to handle the error
 	 * (e.g., SetPageError, set_page_dirty and extra works).
 	 */
-	if (err == 0)
+	if (unlikely(ret < 0))
+		return ret;
+
+	switch (ret) {
+	case 0:
 		page_endio(page, is_write, 0);
-	return err;
+		break;
+	case 1:
+		ret = 0;
+		break;
+	default:
+		WARN_ON(1);
+	}
+	return ret;
 }
 
 static void zram_reset_device(struct zram *zram)
@@ -983,6 +1354,7 @@ static void zram_reset_device(struct zram *zram)
 	zram_meta_free(zram, disksize);
 	memset(&zram->stats, 0, sizeof(zram->stats));
 	zcomp_destroy(comp);
+	reset_bdev(zram);
 }
 
 static ssize_t disksize_store(struct device *dev,
@@ -1108,6 +1480,9 @@ static DEVICE_ATTR_WO(mem_limit);
 static DEVICE_ATTR_WO(mem_used_max);
 static DEVICE_ATTR_RW(max_comp_streams);
 static DEVICE_ATTR_RW(comp_algorithm);
+#ifdef CONFIG_ZRAM_WRITEBACK
+static DEVICE_ATTR_RW(backing_dev);
+#endif
 
 static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_disksize.attr,
@@ -1118,6 +1493,9 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_mem_used_max.attr,
 	&dev_attr_max_comp_streams.attr,
 	&dev_attr_comp_algorithm.attr,
+#ifdef CONFIG_ZRAM_WRITEBACK
+	&dev_attr_backing_dev.attr,
+#endif
 	&dev_attr_io_stat.attr,
 	&dev_attr_mm_stat.attr,
 	&dev_attr_debug_stat.attr,
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index e34e44d02e3e..31762db861e3 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -60,9 +60,10 @@ static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
 
 /* Flags for zram pages (table[page_no].value) */
 enum zram_pageflags {
-	/* Page consists entirely of zeros */
+	/* Page consists the same element */
 	ZRAM_SAME = ZRAM_FLAG_SHIFT,
 	ZRAM_ACCESS,	/* page is now accessed */
+	ZRAM_WB,	/* page is stored on backing_device */
 
 	__NR_ZRAM_PAGEFLAGS,
 };
@@ -115,5 +116,13 @@ struct zram {
 	 * zram is claimed so open request will be failed
 	 */
 	bool claim; /* Protected by bdev->bd_mutex */
+#ifdef CONFIG_ZRAM_WRITEBACK
+	struct file *backing_dev;
+	struct block_device *bdev;
+	unsigned int old_block_size;
+	unsigned long *bitmap;
+	unsigned long nr_pages;
+	spinlock_t bitmap_lock;
+#endif
 };
 #endif
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index a36216bd2a84..e4d4b6b41e26 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -4308,10 +4308,10 @@ i915_drop_caches_set(void *data, u64 val)
 
 	fs_reclaim_acquire(GFP_KERNEL);
 	if (val & DROP_BOUND)
-		i915_gem_shrink(dev_priv, LONG_MAX, I915_SHRINK_BOUND);
+		i915_gem_shrink(dev_priv, LONG_MAX, NULL, I915_SHRINK_BOUND);
 
 	if (val & DROP_UNBOUND)
-		i915_gem_shrink(dev_priv, LONG_MAX, I915_SHRINK_UNBOUND);
+		i915_gem_shrink(dev_priv, LONG_MAX, NULL, I915_SHRINK_UNBOUND);
 
 	if (val & DROP_SHRINK_ALL)
 		i915_gem_shrink_all(dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 60267e375e88..bd74641ab7f6 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3742,6 +3742,7 @@ i915_gem_object_create_internal(struct drm_i915_private *dev_priv,
 /* i915_gem_shrinker.c */
 unsigned long i915_gem_shrink(struct drm_i915_private *dev_priv,
 			      unsigned long target,
+			      unsigned long *nr_scanned,
 			      unsigned flags);
 #define I915_SHRINK_PURGEABLE 0x1
 #define I915_SHRINK_UNBOUND 0x2
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b9e8e0d6e97b..287c6ead95b3 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2354,7 +2354,7 @@ rebuild_st:
 				goto err_sg;
 			}
 
-			i915_gem_shrink(dev_priv, 2 * page_count, *s++);
+			i915_gem_shrink(dev_priv, 2 * page_count, NULL, *s++);
 			cond_resched();
 
 			/* We've tried hard to allocate the memory by reaping
@@ -5015,7 +5015,7 @@ int i915_gem_freeze_late(struct drm_i915_private *dev_priv)
 	 * the objects as well, see i915_gem_freeze()
 	 */
 
-	i915_gem_shrink(dev_priv, -1UL, I915_SHRINK_UNBOUND);
+	i915_gem_shrink(dev_priv, -1UL, NULL, I915_SHRINK_UNBOUND);
 	i915_gem_drain_freed_objects(dev_priv);
 
 	mutex_lock(&dev_priv->drm.struct_mutex);
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index d60f38adc4c4..6c6b8e8592aa 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2062,7 +2062,7 @@ int i915_gem_gtt_prepare_pages(struct drm_i915_gem_object *obj,
 		 */
 		GEM_BUG_ON(obj->mm.pages == pages);
 	} while (i915_gem_shrink(to_i915(obj->base.dev),
-				 obj->base.size >> PAGE_SHIFT,
+				 obj->base.size >> PAGE_SHIFT, NULL,
 				 I915_SHRINK_BOUND |
 				 I915_SHRINK_UNBOUND |
 				 I915_SHRINK_ACTIVE));
diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index 77fb39808131..74002b2d1b6f 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -136,6 +136,7 @@ static bool unsafe_drop_pages(struct drm_i915_gem_object *obj)
  * i915_gem_shrink - Shrink buffer object caches
  * @dev_priv: i915 device
  * @target: amount of memory to make available, in pages
+ * @nr_scanned: optional output for number of pages scanned (incremental)
  * @flags: control flags for selecting cache types
  *
  * This function is the main interface to the shrinker. It will try to release
@@ -158,7 +159,9 @@ static bool unsafe_drop_pages(struct drm_i915_gem_object *obj)
  */
 unsigned long
 i915_gem_shrink(struct drm_i915_private *dev_priv,
-		unsigned long target, unsigned flags)
+		unsigned long target,
+		unsigned long *nr_scanned,
+		unsigned flags)
 {
 	const struct {
 		struct list_head *list;
@@ -169,6 +172,7 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
 		{ NULL, 0 },
 	}, *phase;
 	unsigned long count = 0;
+	unsigned long scanned = 0;
 	bool unlock;
 
 	if (!shrinker_lock(dev_priv, &unlock))
@@ -249,6 +253,7 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
 					count += obj->base.size >> PAGE_SHIFT;
 				}
 				mutex_unlock(&obj->mm.lock);
+				scanned += obj->base.size >> PAGE_SHIFT;
 			}
 		}
 		list_splice_tail(&still_in_list, phase->list);
@@ -261,6 +266,8 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
 
 	shrinker_unlock(dev_priv, unlock);
 
+	if (nr_scanned)
+		*nr_scanned += scanned;
 	return count;
 }
 
@@ -283,7 +290,7 @@ unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
 	unsigned long freed;
 
 	intel_runtime_pm_get(dev_priv);
-	freed = i915_gem_shrink(dev_priv, -1UL,
+	freed = i915_gem_shrink(dev_priv, -1UL, NULL,
 				I915_SHRINK_BOUND |
 				I915_SHRINK_UNBOUND |
 				I915_SHRINK_ACTIVE);
@@ -329,23 +336,28 @@ i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 	unsigned long freed;
 	bool unlock;
 
+	sc->nr_scanned = 0;
+
 	if (!shrinker_lock(dev_priv, &unlock))
 		return SHRINK_STOP;
 
 	freed = i915_gem_shrink(dev_priv,
 				sc->nr_to_scan,
+				&sc->nr_scanned,
 				I915_SHRINK_BOUND |
 				I915_SHRINK_UNBOUND |
 				I915_SHRINK_PURGEABLE);
 	if (freed < sc->nr_to_scan)
 		freed += i915_gem_shrink(dev_priv,
-					 sc->nr_to_scan - freed,
+					 sc->nr_to_scan - sc->nr_scanned,
+					 &sc->nr_scanned,
 					 I915_SHRINK_BOUND |
 					 I915_SHRINK_UNBOUND);
 	if (freed < sc->nr_to_scan && current_is_kswapd()) {
 		intel_runtime_pm_get(dev_priv);
 		freed += i915_gem_shrink(dev_priv,
-					 sc->nr_to_scan - freed,
+					 sc->nr_to_scan - sc->nr_scanned,
+					 &sc->nr_scanned,
 					 I915_SHRINK_ACTIVE |
 					 I915_SHRINK_BOUND |
 					 I915_SHRINK_UNBOUND);
@@ -354,7 +366,7 @@ i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 
 	shrinker_unlock(dev_priv, unlock);
 
-	return freed;
+	return sc->nr_scanned ? freed : SHRINK_STOP;
 }
 
 static bool
@@ -453,7 +465,7 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
 		goto out;
 
 	intel_runtime_pm_get(dev_priv);
-	freed_pages += i915_gem_shrink(dev_priv, -1UL,
+	freed_pages += i915_gem_shrink(dev_priv, -1UL, NULL,
 				       I915_SHRINK_BOUND |
 				       I915_SHRINK_UNBOUND |
 				       I915_SHRINK_ACTIVE |
diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index 14323faf8bd9..60491641a8d6 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -1241,8 +1241,10 @@ static int btt_rw_page(struct block_device *bdev, sector_t sector,
 {
 	struct btt *btt = bdev->bd_disk->private_data;
 	int rc;
+	unsigned int len;
 
-	rc = btt_do_bvec(btt, NULL, page, PAGE_SIZE, 0, is_write, sector);
+	len = hpage_nr_pages(page) * PAGE_SIZE;
+	rc = btt_do_bvec(btt, NULL, page, len, 0, is_write, sector);
 	if (rc == 0)
 		page_endio(page, is_write, 0);
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index f7099adaabc0..e9aa453da50c 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -80,22 +80,40 @@ static blk_status_t pmem_clear_poison(struct pmem_device *pmem,
 static void write_pmem(void *pmem_addr, struct page *page,
 		unsigned int off, unsigned int len)
 {
-	void *mem = kmap_atomic(page);
-
-	memcpy_flushcache(pmem_addr, mem + off, len);
-	kunmap_atomic(mem);
+	unsigned int chunk;
+	void *mem;
+
+	while (len) {
+		mem = kmap_atomic(page);
+		chunk = min_t(unsigned int, len, PAGE_SIZE);
+		memcpy_flushcache(pmem_addr, mem + off, chunk);
+		kunmap_atomic(mem);
+		len -= chunk;
+		off = 0;
+		page++;
+		pmem_addr += PAGE_SIZE;
+	}
 }
 
 static blk_status_t read_pmem(struct page *page, unsigned int off,
 		void *pmem_addr, unsigned int len)
 {
+	unsigned int chunk;
 	int rc;
-	void *mem = kmap_atomic(page);
-
-	rc = memcpy_mcsafe(mem + off, pmem_addr, len);
-	kunmap_atomic(mem);
-	if (rc)
-		return BLK_STS_IOERR;
+	void *mem;
+
+	while (len) {
+		mem = kmap_atomic(page);
+		chunk = min_t(unsigned int, len, PAGE_SIZE);
+		rc = memcpy_mcsafe(mem + off, pmem_addr, chunk);
+		kunmap_atomic(mem);
+		if (rc)
+			return BLK_STS_IOERR;
+		len -= chunk;
+		off = 0;
+		page++;
+		pmem_addr += PAGE_SIZE;
+	}
 	return BLK_STS_OK;
 }
 
@@ -188,7 +206,8 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
 	struct pmem_device *pmem = bdev->bd_queue->queuedata;
 	blk_status_t rc;
 
-	rc = pmem_do_bvec(pmem, page, PAGE_SIZE, 0, is_write, sector);
+	rc = pmem_do_bvec(pmem, page, hpage_nr_pages(page) * PAGE_SIZE,
+			  0, is_write, sector);
 
 	/*
 	 * The ->rw_page interface is subtle and tricky.  The core