diff mbox series

[v13,02/12] bcache: initialize the nvm pages allocator

Message ID 20211212170552.2812-3-colyli@suse.de (mailing list archive)
State New, archived
Headers show
Series bcache for 5.17: enable NVDIMM for bcache journal | expand

Commit Message

Coly Li Dec. 12, 2021, 5:05 p.m. UTC
From: Jianpeng Ma <jianpeng.ma@intel.com>

This patch define the prototype data structures in memory and
initializes the nvm pages allocator.

The nvm address space which is managed by this allocator can consist of
many nvm namespaces, and some namespaces can compose into one nvm set,
like cache set. For this initial implementation, only one set can be
supported.

The users of this nvm pages allocator need to call register_namespace()
to register the nvdimm device (like /dev/pmemX) into this allocator as
the instance of struct nvm_namespace.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jianpeng Ma <jianpeng.ma@intel.com>
Co-developed-by: Qiaowei Ren <qiaowei.ren@intel.com>
Signed-off-by: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
---
 drivers/md/bcache/Kconfig  |  10 ++
 drivers/md/bcache/Makefile |   1 +
 drivers/md/bcache/nvmpg.c  | 340 +++++++++++++++++++++++++++++++++++++
 drivers/md/bcache/nvmpg.h  |  97 +++++++++++
 drivers/md/bcache/super.c  |   3 +
 5 files changed, 451 insertions(+)
 create mode 100644 drivers/md/bcache/nvmpg.c
 create mode 100644 drivers/md/bcache/nvmpg.h

Comments

Jens Axboe Dec. 12, 2021, 7:34 p.m. UTC | #1
On 12/12/21 10:05 AM, Coly Li wrote:
> diff --git a/drivers/md/bcache/nvmpg.c b/drivers/md/bcache/nvmpg.c
> new file mode 100644
> index 000000000000..b654bbbda03e
> --- /dev/null
> +++ b/drivers/md/bcache/nvmpg.c
> @@ -0,0 +1,340 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Nvdimm page-buddy allocator
> + *
> + * Copyright (c) 2021, Intel Corporation.
> + * Copyright (c) 2021, Qiaowei Ren <qiaowei.ren@intel.com>.
> + * Copyright (c) 2021, Jianpeng Ma <jianpeng.ma@intel.com>.
> + */
> +
> +#include "bcache.h"
> +#include "nvmpg.h"
> +
> +#include <linux/slab.h>
> +#include <linux/list.h>
> +#include <linux/mutex.h>
> +#include <linux/dax.h>
> +#include <linux/pfn_t.h>
> +#include <linux/libnvdimm.h>
> +#include <linux/mm_types.h>
> +#include <linux/err.h>
> +#include <linux/pagemap.h>
> +#include <linux/bitmap.h>
> +#include <linux/blkdev.h>
> +
> +struct bch_nvmpg_set *global_nvmpg_set;
> +
> +void *bch_nvmpg_offset_to_ptr(unsigned long offset)
> +{
> +	int ns_id = BCH_NVMPG_GET_NS_ID(offset);
> +	struct bch_nvmpg_ns *ns = global_nvmpg_set->ns_tbl[ns_id];
> +
> +	if (offset == 0)
> +		return NULL;
> +
> +	ns_id = BCH_NVMPG_GET_NS_ID(offset);
> +	ns = global_nvmpg_set->ns_tbl[ns_id];
> +
> +	if (ns)
> +		return (void *)(ns->base_addr + BCH_NVMPG_GET_OFFSET(offset));
> +
> +	pr_err("Invalid ns_id %u\n", ns_id);
> +	return NULL;
> +}
> +
> +unsigned long bch_nvmpg_ptr_to_offset(struct bch_nvmpg_ns *ns, void *ptr)
> +{
> +	int ns_id = ns->ns_id;
> +	unsigned long offset = (unsigned long)(ptr - ns->base_addr);
> +
> +	return BCH_NVMPG_OFFSET(ns_id, offset);
> +}
> +
> +static void release_ns_tbl(struct bch_nvmpg_set *set)
> +{
> +	int i;
> +	struct bch_nvmpg_ns *ns;
> +
> +	for (i = 0; i < BCH_NVMPG_NS_MAX; i++) {
> +		ns = set->ns_tbl[i];
> +		if (ns) {
> +			fs_put_dax(ns->dax_dev);
> +			blkdev_put(ns->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
> +			set->ns_tbl[i] = NULL;
> +			set->attached_ns--;
> +			kfree(ns);
> +		}
> +	}
> +
> +	if (set->attached_ns)
> +		pr_err("unexpected attached_ns: %u\n", set->attached_ns);
> +}
> +
> +static void release_nvmpg_set(struct bch_nvmpg_set *set)
> +{
> +	release_ns_tbl(set);
> +	kfree(set);
> +}
> +
> +/* Namespace 0 contains all meta data of the nvmpg allocation set */
> +static int init_nvmpg_set_header(struct bch_nvmpg_ns *ns)
> +{
> +	struct bch_nvmpg_set_header *set_header;
> +
> +	if (ns->ns_id != 0) {
> +		pr_err("unexpected ns_id %u for first nvmpg namespace.\n",
> +		       ns->ns_id);
> +		return -EINVAL;
> +	}
> +
> +	set_header = bch_nvmpg_offset_to_ptr(ns->sb->set_header_offset);
> +
> +	mutex_lock(&global_nvmpg_set->lock);
> +	global_nvmpg_set->set_header = set_header;
> +	global_nvmpg_set->heads_size = set_header->size;
> +	global_nvmpg_set->heads_used = set_header->used;
> +	mutex_unlock(&global_nvmpg_set->lock);
> +
> +	return 0;
> +}
> +
> +static int attach_nvmpg_set(struct bch_nvmpg_ns *ns)
> +{
> +	struct bch_nvmpg_sb *sb = ns->sb;
> +	int rc = 0;
> +
> +	mutex_lock(&global_nvmpg_set->lock);
> +
> +	if (global_nvmpg_set->ns_tbl[sb->this_ns]) {
> +		pr_err("ns_id %u already attached.\n", ns->ns_id);
> +		rc = -EEXIST;
> +		goto unlock;
> +	}
> +
> +	if (ns->ns_id != 0) {
> +		pr_err("unexpected ns_id %u for first namespace.\n", ns->ns_id);
> +		rc = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	if (global_nvmpg_set->attached_ns > 0) {
> +		pr_err("multiple namespace attaching not supported yet\n");
> +		rc = -EOPNOTSUPP;
> +		goto unlock;
> +	}
> +
> +	if ((global_nvmpg_set->attached_ns + 1) > sb->total_ns) {
> +		pr_err("namespace counters error: attached %u > total %u\n",
> +		       global_nvmpg_set->attached_ns,
> +		       global_nvmpg_set->total_ns);
> +		rc = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	memcpy(global_nvmpg_set->set_uuid, sb->set_uuid, 16);
> +	global_nvmpg_set->ns_tbl[sb->this_ns] = ns;
> +	global_nvmpg_set->attached_ns++;
> +	global_nvmpg_set->total_ns = sb->total_ns;
> +
> +unlock:
> +	mutex_unlock(&global_nvmpg_set->lock);
> +	return rc;
> +}
> +
> +static int read_nvdimm_meta_super(struct block_device *bdev,
> +				  struct bch_nvmpg_ns *ns)
> +{
> +	struct page *page;
> +	struct bch_nvmpg_sb *sb;
> +	uint64_t expected_csum = 0;
> +	int r;
> +
> +	page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
> +				BCH_NVMPG_SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
> +
> +	if (IS_ERR(page))
> +		return -EIO;
> +
> +	sb = (struct bch_nvmpg_sb *)
> +	     (page_address(page) + offset_in_page(BCH_NVMPG_SB_OFFSET));
> +
> +	r = -EINVAL;
> +	expected_csum = csum_set(sb);
> +	if (expected_csum != sb->csum) {
> +		pr_info("csum is not match with expected one\n");

"Checksum mismatch"

would be more correct english, should it print the checksums as well?

> +		goto put_page;
> +	}
> +
> +	if (memcmp(sb->magic, bch_nvmpg_magic, 16)) {
> +		pr_info("invalid bch_nvmpg_magic\n");
> +		goto put_page;
> +	}
> +
> +	if (sb->sb_offset !=
> +	    BCH_NVMPG_OFFSET(sb->this_ns, BCH_NVMPG_SB_OFFSET)) {
> +		pr_info("invalid superblock offset 0x%llx\n", sb->sb_offset);
> +		goto put_page;
> +	}
> +
> +	r = -EOPNOTSUPP;
> +	if (sb->total_ns != 1) {
> +		pr_info("multiple name space not supported yet.\n");
> +		goto put_page;
> +	}

Please use namespace consistently.

> +struct bch_nvmpg_ns *bch_register_namespace(const char *dev_path)
> +{
> +	struct bch_nvmpg_ns *ns = NULL;
> +	struct bch_nvmpg_sb *sb = NULL;
> +	char buf[BDEVNAME_SIZE];
> +	struct block_device *bdev;
> +	pgoff_t pgoff;
> +	int id, err;
> +	char *path;
> +	long dax_ret = 0;
> +
> +	path = kstrndup(dev_path, 512, GFP_KERNEL);
> +	if (!path) {
> +		pr_err("kstrndup failed\n");
> +		return ERR_PTR(-ENOMEM);
> +	}

Really don't think we need that piece of information. Same for a lot of
other places, you have a ton of pr_err() stuff that looks mostly like
debugging.

> +	ns->page_size = sb->page_size;
> +	ns->pages_offset = sb->pages_offset;
> +	ns->pages_total = sb->pages_total;
> +	ns->sb = sb;
> +	ns->free = 0;
> +	ns->bdev = bdev;
> +	ns->set = global_nvmpg_set;
> +
> +	err = attach_nvmpg_set(ns);
> +	if (err < 0)
> +		goto free_ns;
> +
> +	mutex_init(&ns->lock);
> +
> +	err = init_nvmpg_set_header(ns);
> +	if (err < 0)
> +		goto free_ns;

Does this error path need to un-attach?
> +int __init bch_nvmpg_init(void)
> +{
> +	global_nvmpg_set = kzalloc(sizeof(*global_nvmpg_set), GFP_KERNEL);
> +	if (!global_nvmpg_set)
> +		return -ENOMEM;
> +
> +	global_nvmpg_set->total_ns = 0;
> +	mutex_init(&global_nvmpg_set->lock);
> +
> +	pr_info("bcache nvm init\n");

Another useless pr debug print, just get rid of it (and others).

> +void bch_nvmpg_exit(void)
> +{
> +	release_nvmpg_set(global_nvmpg_set);
> +	pr_info("bcache nvm exit\n");
> +}

Ditto
Coly Li Dec. 28, 2021, 5:29 a.m. UTC | #2
Hi Jens,

Thank you for review the patches. I was in travel for a week when you 
replied the email and after the travel I was sick for one more week. 
Just being able to sit in front of my laptop now.

I reply inline bellow your comments.

On 12/13/21 3:34 AM, Jens Axboe wrote:
> On 12/12/21 10:05 AM, Coly Li wrote:
>> diff --git a/drivers/md/bcache/nvmpg.c b/drivers/md/bcache/nvmpg.c
>> new file mode 100644
>> index 000000000000..b654bbbda03e
>> --- /dev/null
>> +++ b/drivers/md/bcache/nvmpg.c
>> @@ -0,0 +1,340 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Nvdimm page-buddy allocator
>> + *
>> + * Copyright (c) 2021, Intel Corporation.
>> + * Copyright (c) 2021, Qiaowei Ren<qiaowei.ren@intel.com>.
>> + * Copyright (c) 2021, Jianpeng Ma<jianpeng.ma@intel.com>.
>> + */
>> +
>> +#include "bcache.h"
>> +#include "nvmpg.h"
>> +
>> +#include <linux/slab.h>
>> +#include <linux/list.h>
>> +#include <linux/mutex.h>
>> +#include <linux/dax.h>
>> +#include <linux/pfn_t.h>
>> +#include <linux/libnvdimm.h>
>> +#include <linux/mm_types.h>
>> +#include <linux/err.h>
>> +#include <linux/pagemap.h>
>> +#include <linux/bitmap.h>
>> +#include <linux/blkdev.h>
>> +
[snipped]
>> +	expected_csum = csum_set(sb);
>> +	if (expected_csum != sb->csum) {
>> +		pr_info("csum is not match with expected one\n");
> "Checksum mismatch"

Copied, it will be fixed.


> would be more correct english, should it print the checksums as well?

This is the style following bcache code to report bad check sum, like,
super.c:718:                pr_warn("bad csum reading priorities\n");
journal.c:141:                pr_info("%u: bad csum, %zu bytes, offset 
%u\n",

There might be fine to only notice the bad csum status.

>> +		goto put_page;
>> +	}
>> +
>> +	if (memcmp(sb->magic, bch_nvmpg_magic, 16)) {
>> +		pr_info("invalid bch_nvmpg_magic\n");
>> +		goto put_page;
>> +	}
>> +
>> +	if (sb->sb_offset !=
>> +	    BCH_NVMPG_OFFSET(sb->this_ns, BCH_NVMPG_SB_OFFSET)) {
>> +		pr_info("invalid superblock offset 0x%llx\n", sb->sb_offset);
>> +		goto put_page;
>> +	}
>> +
>> +	r = -EOPNOTSUPP;
>> +	if (sb->total_ns != 1) {
>> +		pr_info("multiple name space not supported yet.\n");
>> +		goto put_page;
>> +	}
> Please use namespace consistently.

Copied, it will be fixed.

>> +struct bch_nvmpg_ns *bch_register_namespace(const char *dev_path)
>> +{
>> +	struct bch_nvmpg_ns *ns = NULL;
>> +	struct bch_nvmpg_sb *sb = NULL;
>> +	char buf[BDEVNAME_SIZE];
>> +	struct block_device *bdev;
>> +	pgoff_t pgoff;
>> +	int id, err;
>> +	char *path;
>> +	long dax_ret = 0;
>> +
>> +	path = kstrndup(dev_path, 512, GFP_KERNEL);
>> +	if (!path) {
>> +		pr_err("kstrndup failed\n");
>> +		return ERR_PTR(-ENOMEM);
>> +	}
> Really don't think we need that piece of information. Same for a lot of
> other places, you have a ton of pr_err() stuff that looks mostly like
> debugging.

Hmm, I think I need your guidance here. When I review the code, IMHO the 
error message is necessary but don't print them in run time code. Such 
place is in NVDIMM namespace registration code path, therefore I 
accepted it. This is what I was trained for long time....

Could you please give me some hint to judge whether a printk message 
should be avoided? Then I will use it in future code review and my own 
coding work.


>> +	ns->page_size = sb->page_size;
>> +	ns->pages_offset = sb->pages_offset;
>> +	ns->pages_total = sb->pages_total;
>> +	ns->sb = sb;
>> +	ns->free = 0;
>> +	ns->bdev = bdev;
>> +	ns->set = global_nvmpg_set;
>> +
>> +	err = attach_nvmpg_set(ns);
>> +	if (err < 0)
>> +		goto free_ns;
>> +
>> +	mutex_init(&ns->lock);
>> +
>> +	err = init_nvmpg_set_header(ns);
>> +	if (err < 0)
>> +		goto free_ns;
> Does this error path need to un-attach?

Detach or un-attach is not implemented in this series, because it is 
related to how to flush the whole NVDIMM namespace during un-attach. It 
is planed to posted with the NVDIMM support for Bcache B+tree node.

For current bcache code only with SSD, if a flush request received from 
upper layer, it is synchronously sent to backing device and 
asynchronously sent to cache device with journal flush. But for NVDIMM 
namespace, such operation is to flush last level cache, we have 3 
candidate methods to handle,
1) flush cache for the whole dax mapped linear address range (like 
nvdimm_flush() in libnvdimm)
2) flush cache for the only allocated NVDIMM ranges in the nvmpg 
allocator for selected requesters (uuids).
3) maintain a list of dirty NVDIMM pages, and only flush cache for these 
linear address ranges.

We are still testing the performance and not make decision yet. So the 
detach code path is not posted in this series and we un-attach the 
NVDIMM namespace by unloading bcache kernel module currently.

>> +int __init bch_nvmpg_init(void)
>> +{
>> +	global_nvmpg_set = kzalloc(sizeof(*global_nvmpg_set), GFP_KERNEL);
>> +	if (!global_nvmpg_set)
>> +		return -ENOMEM;
>> +
>> +	global_nvmpg_set->total_ns = 0;
>> +	mutex_init(&global_nvmpg_set->lock);
>> +
>> +	pr_info("bcache nvm init\n");
> Another useless pr debug print, just get rid of it (and others).

Copied, it will be dropped.

>> +void bch_nvmpg_exit(void)
>> +{
>> +	release_nvmpg_set(global_nvmpg_set);
>> +	pr_info("bcache nvm exit\n");
>> +}
> Ditto

Copied.

Thanks for your comments.

Coly Li
diff mbox series

Patch

diff --git a/drivers/md/bcache/Kconfig b/drivers/md/bcache/Kconfig
index cf3e8096942a..4a7c13e882bb 100644
--- a/drivers/md/bcache/Kconfig
+++ b/drivers/md/bcache/Kconfig
@@ -36,3 +36,13 @@  config BCACHE_ASYNC_REGISTRATION
 	device path into this file will returns immediately and the real
 	registration work is handled in kernel work queue in asynchronous
 	way.
+
+config BCACHE_NVM_PAGES
+	bool "NVDIMM support for bcache (EXPERIMENTAL)"
+	depends on BCACHE
+	depends on 64BIT
+	depends on LIBNVDIMM
+	depends on DAX
+	help
+	  Allocate/release NV-memory pages for bcache and provide allocated pages
+	  for each requestor after system reboot.
diff --git a/drivers/md/bcache/Makefile b/drivers/md/bcache/Makefile
index 5b87e59676b8..276b33be5ad5 100644
--- a/drivers/md/bcache/Makefile
+++ b/drivers/md/bcache/Makefile
@@ -5,3 +5,4 @@  obj-$(CONFIG_BCACHE)	+= bcache.o
 bcache-y		:= alloc.o bset.o btree.o closure.o debug.o extents.o\
 	io.o journal.o movinggc.o request.o stats.o super.o sysfs.o trace.o\
 	util.o writeback.o features.o
+bcache-$(CONFIG_BCACHE_NVM_PAGES) += nvmpg.o
diff --git a/drivers/md/bcache/nvmpg.c b/drivers/md/bcache/nvmpg.c
new file mode 100644
index 000000000000..b654bbbda03e
--- /dev/null
+++ b/drivers/md/bcache/nvmpg.c
@@ -0,0 +1,340 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nvdimm page-buddy allocator
+ *
+ * Copyright (c) 2021, Intel Corporation.
+ * Copyright (c) 2021, Qiaowei Ren <qiaowei.ren@intel.com>.
+ * Copyright (c) 2021, Jianpeng Ma <jianpeng.ma@intel.com>.
+ */
+
+#include "bcache.h"
+#include "nvmpg.h"
+
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/dax.h>
+#include <linux/pfn_t.h>
+#include <linux/libnvdimm.h>
+#include <linux/mm_types.h>
+#include <linux/err.h>
+#include <linux/pagemap.h>
+#include <linux/bitmap.h>
+#include <linux/blkdev.h>
+
+struct bch_nvmpg_set *global_nvmpg_set;
+
+void *bch_nvmpg_offset_to_ptr(unsigned long offset)
+{
+	int ns_id = BCH_NVMPG_GET_NS_ID(offset);
+	struct bch_nvmpg_ns *ns = global_nvmpg_set->ns_tbl[ns_id];
+
+	if (offset == 0)
+		return NULL;
+
+	ns_id = BCH_NVMPG_GET_NS_ID(offset);
+	ns = global_nvmpg_set->ns_tbl[ns_id];
+
+	if (ns)
+		return (void *)(ns->base_addr + BCH_NVMPG_GET_OFFSET(offset));
+
+	pr_err("Invalid ns_id %u\n", ns_id);
+	return NULL;
+}
+
+unsigned long bch_nvmpg_ptr_to_offset(struct bch_nvmpg_ns *ns, void *ptr)
+{
+	int ns_id = ns->ns_id;
+	unsigned long offset = (unsigned long)(ptr - ns->base_addr);
+
+	return BCH_NVMPG_OFFSET(ns_id, offset);
+}
+
+static void release_ns_tbl(struct bch_nvmpg_set *set)
+{
+	int i;
+	struct bch_nvmpg_ns *ns;
+
+	for (i = 0; i < BCH_NVMPG_NS_MAX; i++) {
+		ns = set->ns_tbl[i];
+		if (ns) {
+			fs_put_dax(ns->dax_dev);
+			blkdev_put(ns->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+			set->ns_tbl[i] = NULL;
+			set->attached_ns--;
+			kfree(ns);
+		}
+	}
+
+	if (set->attached_ns)
+		pr_err("unexpected attached_ns: %u\n", set->attached_ns);
+}
+
+static void release_nvmpg_set(struct bch_nvmpg_set *set)
+{
+	release_ns_tbl(set);
+	kfree(set);
+}
+
+/* Namespace 0 contains all meta data of the nvmpg allocation set */
+static int init_nvmpg_set_header(struct bch_nvmpg_ns *ns)
+{
+	struct bch_nvmpg_set_header *set_header;
+
+	if (ns->ns_id != 0) {
+		pr_err("unexpected ns_id %u for first nvmpg namespace.\n",
+		       ns->ns_id);
+		return -EINVAL;
+	}
+
+	set_header = bch_nvmpg_offset_to_ptr(ns->sb->set_header_offset);
+
+	mutex_lock(&global_nvmpg_set->lock);
+	global_nvmpg_set->set_header = set_header;
+	global_nvmpg_set->heads_size = set_header->size;
+	global_nvmpg_set->heads_used = set_header->used;
+	mutex_unlock(&global_nvmpg_set->lock);
+
+	return 0;
+}
+
+static int attach_nvmpg_set(struct bch_nvmpg_ns *ns)
+{
+	struct bch_nvmpg_sb *sb = ns->sb;
+	int rc = 0;
+
+	mutex_lock(&global_nvmpg_set->lock);
+
+	if (global_nvmpg_set->ns_tbl[sb->this_ns]) {
+		pr_err("ns_id %u already attached.\n", ns->ns_id);
+		rc = -EEXIST;
+		goto unlock;
+	}
+
+	if (ns->ns_id != 0) {
+		pr_err("unexpected ns_id %u for first namespace.\n", ns->ns_id);
+		rc = -EINVAL;
+		goto unlock;
+	}
+
+	if (global_nvmpg_set->attached_ns > 0) {
+		pr_err("multiple namespace attaching not supported yet\n");
+		rc = -EOPNOTSUPP;
+		goto unlock;
+	}
+
+	if ((global_nvmpg_set->attached_ns + 1) > sb->total_ns) {
+		pr_err("namespace counters error: attached %u > total %u\n",
+		       global_nvmpg_set->attached_ns,
+		       global_nvmpg_set->total_ns);
+		rc = -EINVAL;
+		goto unlock;
+	}
+
+	memcpy(global_nvmpg_set->set_uuid, sb->set_uuid, 16);
+	global_nvmpg_set->ns_tbl[sb->this_ns] = ns;
+	global_nvmpg_set->attached_ns++;
+	global_nvmpg_set->total_ns = sb->total_ns;
+
+unlock:
+	mutex_unlock(&global_nvmpg_set->lock);
+	return rc;
+}
+
+static int read_nvdimm_meta_super(struct block_device *bdev,
+				  struct bch_nvmpg_ns *ns)
+{
+	struct page *page;
+	struct bch_nvmpg_sb *sb;
+	uint64_t expected_csum = 0;
+	int r;
+
+	page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
+				BCH_NVMPG_SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
+
+	if (IS_ERR(page))
+		return -EIO;
+
+	sb = (struct bch_nvmpg_sb *)
+	     (page_address(page) + offset_in_page(BCH_NVMPG_SB_OFFSET));
+
+	r = -EINVAL;
+	expected_csum = csum_set(sb);
+	if (expected_csum != sb->csum) {
+		pr_info("csum is not match with expected one\n");
+		goto put_page;
+	}
+
+	if (memcmp(sb->magic, bch_nvmpg_magic, 16)) {
+		pr_info("invalid bch_nvmpg_magic\n");
+		goto put_page;
+	}
+
+	if (sb->sb_offset !=
+	    BCH_NVMPG_OFFSET(sb->this_ns, BCH_NVMPG_SB_OFFSET)) {
+		pr_info("invalid superblock offset 0x%llx\n", sb->sb_offset);
+		goto put_page;
+	}
+
+	r = -EOPNOTSUPP;
+	if (sb->total_ns != 1) {
+		pr_info("multiple name space not supported yet.\n");
+		goto put_page;
+	}
+
+
+	r = 0;
+	/* Necessary for DAX mapping */
+	ns->page_size = sb->page_size;
+	ns->pages_total = sb->pages_total;
+
+put_page:
+	put_page(page);
+	return r;
+}
+
+struct bch_nvmpg_ns *bch_register_namespace(const char *dev_path)
+{
+	struct bch_nvmpg_ns *ns = NULL;
+	struct bch_nvmpg_sb *sb = NULL;
+	char buf[BDEVNAME_SIZE];
+	struct block_device *bdev;
+	pgoff_t pgoff;
+	int id, err;
+	char *path;
+	long dax_ret = 0;
+
+	path = kstrndup(dev_path, 512, GFP_KERNEL);
+	if (!path) {
+		pr_err("kstrndup failed\n");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	bdev = blkdev_get_by_path(strim(path),
+				  FMODE_READ|FMODE_WRITE|FMODE_EXCL,
+				  global_nvmpg_set);
+	if (IS_ERR(bdev)) {
+		pr_err("get %s error: %ld\n", dev_path, PTR_ERR(bdev));
+		kfree(path);
+		return ERR_PTR(PTR_ERR(bdev));
+	}
+
+	err = -ENOMEM;
+	ns = kzalloc(sizeof(struct bch_nvmpg_ns), GFP_KERNEL);
+	if (!ns)
+		goto bdput;
+
+	err = -EIO;
+	if (read_nvdimm_meta_super(bdev, ns)) {
+		pr_err("%s read nvdimm meta super block failed.\n",
+		       bdevname(bdev, buf));
+		goto free_ns;
+	}
+
+	err = -EOPNOTSUPP;
+	ns->dax_dev = fs_dax_get_by_bdev(bdev);
+	if (!ns->dax_dev) {
+		pr_err("can't get dax device by %s\n", bdevname(bdev, buf));
+		goto free_ns;
+	}
+
+	if (!dax_supported(ns->dax_dev, bdev, ns->page_size, 0,
+			   bdev_nr_sectors(bdev))) {
+		pr_err("%s don't support DAX\n", bdevname(bdev, buf));
+		goto free_ns;
+	}
+
+	err = -EINVAL;
+	if (bdev_dax_pgoff(bdev, 0, ns->page_size, &pgoff)) {
+		pr_err("invalid offset of %s\n", bdevname(bdev, buf));
+		goto free_ns;
+	}
+
+	err = -EINVAL;
+	id = dax_read_lock();
+	dax_ret = dax_direct_access(ns->dax_dev, pgoff, ns->pages_total,
+				    &ns->base_addr, &ns->start_pfn);
+	if (dax_ret <= 0) {
+		pr_err("dax_direct_access error\n");
+		dax_read_unlock(id);
+		goto free_ns;
+	}
+
+	if (dax_ret < ns->pages_total) {
+		pr_warn("currently first %ld pages (from %lu in total) are used\n",
+			dax_ret, ns->pages_total);
+	}
+	dax_read_unlock(id);
+
+	sb = (struct bch_nvmpg_sb *)(ns->base_addr + BCH_NVMPG_SB_OFFSET);
+
+	err = -EINVAL;
+	/* Check magic again to make sure DAX mapping is correct */
+	if (memcmp(sb->magic, bch_nvmpg_magic, 16)) {
+		pr_err("invalid bch_nvmpg_magic after DAX mapping\n");
+		goto free_ns;
+	}
+
+	if ((global_nvmpg_set->attached_ns > 0) &&
+	     memcmp(sb->set_uuid, global_nvmpg_set->set_uuid, 16)) {
+		pr_err("set uuid does not match with ns_id %u\n", ns->ns_id);
+		goto free_ns;
+	}
+
+	if (sb->set_header_offset !=
+	    BCH_NVMPG_OFFSET(sb->this_ns, BCH_NVMPG_RECLIST_HEAD_OFFSET)) {
+		pr_err("Invalid header offset: this_ns %u, ns_id %llu, offset 0x%llx\n",
+		       sb->this_ns,
+		       BCH_NVMPG_GET_NS_ID(sb->set_header_offset),
+		       BCH_NVMPG_GET_OFFSET(sb->set_header_offset));
+		goto free_ns;
+	}
+
+	ns->page_size = sb->page_size;
+	ns->pages_offset = sb->pages_offset;
+	ns->pages_total = sb->pages_total;
+	ns->sb = sb;
+	ns->free = 0;
+	ns->bdev = bdev;
+	ns->set = global_nvmpg_set;
+
+	err = attach_nvmpg_set(ns);
+	if (err < 0)
+		goto free_ns;
+
+	mutex_init(&ns->lock);
+
+	err = init_nvmpg_set_header(ns);
+	if (err < 0)
+		goto free_ns;
+
+	kfree(path);
+	return ns;
+
+free_ns:
+	fs_put_dax(ns->dax_dev);
+	kfree(ns);
+bdput:
+	blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+	kfree(path);
+	return ERR_PTR(err);
+}
+
+int __init bch_nvmpg_init(void)
+{
+	global_nvmpg_set = kzalloc(sizeof(*global_nvmpg_set), GFP_KERNEL);
+	if (!global_nvmpg_set)
+		return -ENOMEM;
+
+	global_nvmpg_set->total_ns = 0;
+	mutex_init(&global_nvmpg_set->lock);
+
+	pr_info("bcache nvm init\n");
+	return 0;
+}
+
+void bch_nvmpg_exit(void)
+{
+	release_nvmpg_set(global_nvmpg_set);
+	pr_info("bcache nvm exit\n");
+}
diff --git a/drivers/md/bcache/nvmpg.h b/drivers/md/bcache/nvmpg.h
new file mode 100644
index 000000000000..698c890b2d15
--- /dev/null
+++ b/drivers/md/bcache/nvmpg.h
@@ -0,0 +1,97 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _BCACHE_NVM_PAGES_H
+#define _BCACHE_NVM_PAGES_H
+
+#include <linux/libnvdimm.h>
+
+#include "nvmpg_format.h"
+
+/*
+ * Bcache NVDIMM in memory data structures
+ */
+
+/*
+ * The following three structures in memory records which page(s) allocated
+ * to which owner. After reboot from power failure, they will be initialized
+ * based on nvm pages superblock in NVDIMM device.
+ */
+struct bch_nvmpg_ns {
+	struct bch_nvmpg_sb *sb;
+	void *base_addr;
+
+	unsigned char uuid[16];
+	int ns_id;
+	unsigned int page_size;
+	unsigned long free;
+	unsigned long pages_offset;
+	unsigned long pages_total;
+	pfn_t start_pfn;
+
+	struct dax_device *dax_dev;
+	struct block_device *bdev;
+	struct bch_nvmpg_set *set;
+
+	struct mutex lock;
+};
+
+/*
+ * A set of namespaces. Currently only one set can be supported.
+ */
+struct bch_nvmpg_set {
+	unsigned char set_uuid[16];
+
+	int heads_size;
+	int heads_used;
+	struct bch_nvmpg_set_header *set_header;
+
+	struct bch_nvmpg_ns *ns_tbl[BCH_NVMPG_NS_MAX];
+	int total_ns;
+	int attached_ns;
+
+	struct mutex lock;
+};
+
+#define BCH_NVMPG_NS_ID_BITS	3
+#define BCH_NVMPG_OFFSET_BITS	61
+#define BCH_NVMPG_NS_ID_MASK	((1UL<<BCH_NVMPG_NS_ID_BITS) - 1)
+#define BCH_NVMPG_OFFSET_MASK	((1UL<<BCH_NVMPG_OFFSET_BITS) - 1)
+
+#define BCH_NVMPG_GET_NS_ID(offset)					\
+	(((offset) >> BCH_NVMPG_OFFSET_BITS) & BCH_NVMPG_NS_ID_MASK)
+
+#define BCH_NVMPG_GET_OFFSET(offset)	((offset) & BCH_NVMPG_OFFSET_MASK)
+
+#define BCH_NVMPG_OFFSET(ns_id, offset)					\
+	((((ns_id) & BCH_NVMPG_NS_ID_MASK) << BCH_NVMPG_OFFSET_BITS) |	\
+	 ((offset) & BCH_NVMPG_OFFSET_MASK))
+
+/* Indicate which field in bch_nvmpg_sb to be updated */
+#define BCH_NVMPG_TOTAL_NS	0	/* total_ns */
+
+void *bch_nvmpg_offset_to_ptr(unsigned long offset);
+unsigned long bch_nvmpg_ptr_to_offset(struct bch_nvmpg_ns *ns, void *ptr);
+
+#if defined(CONFIG_BCACHE_NVM_PAGES)
+
+struct bch_nvmpg_ns *bch_register_namespace(const char *dev_path);
+int bch_nvmpg_init(void);
+void bch_nvmpg_exit(void);
+
+#else
+
+static inline struct bch_nvmpg_ns *bch_register_namespace(const char *dev_path)
+{
+	return NULL;
+}
+
+static inline int bch_nvmpg_init(void)
+{
+	return 0;
+}
+
+static inline void bch_nvmpg_exit(void) { }
+
+#endif /* CONFIG_BCACHE_NVM_PAGES */
+
+#endif /* _BCACHE_NVM_PAGES_H */
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 86b9e355c583..74d51a0b806f 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -14,6 +14,7 @@ 
 #include "request.h"
 #include "writeback.h"
 #include "features.h"
+#include "nvmpg.h"
 
 #include <linux/blkdev.h>
 #include <linux/pagemap.h>
@@ -2818,6 +2819,7 @@  static void bcache_exit(void)
 {
 	bch_debug_exit();
 	bch_request_exit();
+	bch_nvmpg_exit();
 	if (bcache_kobj)
 		kobject_put(bcache_kobj);
 	if (bcache_wq)
@@ -2916,6 +2918,7 @@  static int __init bcache_init(void)
 
 	bch_debug_init();
 	closure_debug_init();
+	bch_nvmpg_init();
 
 	bcache_is_reboot = false;