diff mbox series

[v13,9/9] null_blk: add support for copy offload

Message ID 20230627183629.26571-10-nj.shetty@samsung.com (mailing list archive)
State New, archived
Headers show
Series Implement copy offload support | expand

Commit Message

Nitesh Shetty June 27, 2023, 6:36 p.m. UTC 
Implementaion is based on existing read and write infrastructure.
copy_max_bytes: A new configfs and module parameter is introduced, which
can be used to set hardware/driver supported maximum copy limit.

Suggested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
---
 Documentation/block/null_blk.rst  |  5 ++
 drivers/block/null_blk/main.c     | 85 +++++++++++++++++++++++++++++--
 drivers/block/null_blk/null_blk.h |  1 +
 3 files changed, 88 insertions(+), 3 deletions(-)

Comments

kernel test robot June 28, 2023, 12:11 p.m. UTC | #1 
Hi Nitesh,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 53cdf865f90ba922a854c65ed05b519f9d728424]

url:    https://github.com/intel-lab-lkp/linux/commits/Nitesh-Shetty/block-Introduce-queue-limits-for-copy-offload-support/20230628-163126
base:   53cdf865f90ba922a854c65ed05b519f9d728424
patch link:    https://lore.kernel.org/r/20230627183629.26571-10-nj.shetty%40samsung.com
patch subject: [PATCH v13 9/9] null_blk: add support for copy offload
config: hexagon-randconfig-r045-20230628 (https://download.01.org/0day-ci/archive/20230628/202306281909.TRNCf5eG-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a)
reproduce: (https://download.01.org/0day-ci/archive/20230628/202306281909.TRNCf5eG-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202306281909.TRNCf5eG-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/block/null_blk/main.c:12:
   In file included from drivers/block/null_blk/null_blk.h:8:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     547 |         val = __raw_readb(PCI_IOBASE + addr);
         |                           ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     560 |         val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
      37 | #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
         |                                                   ^
   In file included from drivers/block/null_blk/main.c:12:
   In file included from drivers/block/null_blk/null_blk.h:8:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     573 |         val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
      35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
         |                                                   ^
   In file included from drivers/block/null_blk/main.c:12:
   In file included from drivers/block/null_blk/null_blk.h:8:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     584 |         __raw_writeb(value, PCI_IOBASE + addr);
         |                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     594 |         __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     604 |         __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
>> drivers/block/null_blk/main.c:1295:2: warning: variable 'rem' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
    1295 |         __rq_for_each_bio(bio, req) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/blk-mq.h:1012:2: note: expanded from macro '__rq_for_each_bio'
    1012 |         if ((rq->bio))                  \
         |         ^~~~~~~~~~~~~~
   include/linux/compiler.h:55:28: note: expanded from macro 'if'
      55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
         |                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:57:30: note: expanded from macro '__trace_if_var'
      57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
         |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/block/null_blk/main.c:1300:15: note: uninitialized use occurs here
    1300 |         if (WARN_ON(!rem))
         |                      ^~~
   include/asm-generic/bug.h:123:25: note: expanded from macro 'WARN_ON'
     123 |         int __ret_warn_on = !!(condition);                              \
         |                                ^~~~~~~~~
   include/linux/compiler.h:55:47: note: expanded from macro 'if'
      55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
         |                                               ^~~~
   include/linux/compiler.h:57:52: note: expanded from macro '__trace_if_var'
      57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
         |                                                    ^~~~
   drivers/block/null_blk/main.c:1295:2: note: remove the 'if' if its condition is always true
    1295 |         __rq_for_each_bio(bio, req) {
         |         ^
   include/linux/blk-mq.h:1012:2: note: expanded from macro '__rq_for_each_bio'
    1012 |         if ((rq->bio))                  \
         |         ^
   include/linux/compiler.h:55:23: note: expanded from macro 'if'
      55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
         |                       ^
   drivers/block/null_blk/main.c:1287:12: note: initialize the variable 'rem' to silence this warning
    1287 |         size_t rem, temp;
         |                   ^
         |                    = 0
   7 warnings generated.


vim +1295 drivers/block/null_blk/main.c

  1281	
  1282	static inline int nullb_setup_copy_write(struct nullb *nullb,
  1283			struct request *req, bool is_fua)
  1284	{
  1285		sector_t sector_in, sector_out;
  1286		void *in, *out;
  1287		size_t rem, temp;
  1288		struct bio *bio;
  1289		unsigned long offset_in, offset_out;
  1290		struct nullb_page *t_page_in, *t_page_out;
  1291		int ret = -EIO;
  1292	
  1293		sector_out = blk_rq_pos(req);
  1294	
> 1295		__rq_for_each_bio(bio, req) {
  1296			sector_in = bio->bi_iter.bi_sector;
  1297			rem = bio->bi_iter.bi_size;
  1298		}
  1299	
  1300		if (WARN_ON(!rem))
  1301			return BLK_STS_NOTSUPP;
  1302	
  1303		spin_lock_irq(&nullb->lock);
  1304		while (rem > 0) {
  1305			temp = min_t(size_t, nullb->dev->blocksize, rem);
  1306			offset_in = (sector_in & SECTOR_MASK) << SECTOR_SHIFT;
  1307			offset_out = (sector_out & SECTOR_MASK) << SECTOR_SHIFT;
  1308	
  1309			if (null_cache_active(nullb) && !is_fua)
  1310				null_make_cache_space(nullb, PAGE_SIZE);
  1311	
  1312			t_page_in = null_lookup_page(nullb, sector_in, false,
  1313				!null_cache_active(nullb));
  1314			if (!t_page_in)
  1315				goto err;
  1316			t_page_out = null_insert_page(nullb, sector_out,
  1317				!null_cache_active(nullb) || is_fua);
  1318			if (!t_page_out)
  1319				goto err;
  1320	
  1321			in = kmap_local_page(t_page_in->page);
  1322			out = kmap_local_page(t_page_out->page);
  1323	
  1324			memcpy(out + offset_out, in + offset_in, temp);
  1325			kunmap_local(out);
  1326			kunmap_local(in);
  1327			__set_bit(sector_out & SECTOR_MASK, t_page_out->bitmap);
  1328	
  1329			if (is_fua)
  1330				null_free_sector(nullb, sector_out, true);
  1331	
  1332			rem -= temp;
  1333			sector_in += temp >> SECTOR_SHIFT;
  1334			sector_out += temp >> SECTOR_SHIFT;
  1335		}
  1336	
  1337		ret = 0;
  1338	err:
  1339		spin_unlock_irq(&nullb->lock);
  1340		return ret;
  1341	}
  1342
kernel test robot June 28, 2023, 12:52 p.m. UTC | #2 
Hi Nitesh,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 53cdf865f90ba922a854c65ed05b519f9d728424]

url:    https://github.com/intel-lab-lkp/linux/commits/Nitesh-Shetty/block-Introduce-queue-limits-for-copy-offload-support/20230628-163126
base:   53cdf865f90ba922a854c65ed05b519f9d728424
patch link:    https://lore.kernel.org/r/20230627183629.26571-10-nj.shetty%40samsung.com
patch subject: [PATCH v13 9/9] null_blk: add support for copy offload
config: i386-randconfig-i006-20230628 (https://download.01.org/0day-ci/archive/20230628/202306282001.ba1qWTf0-lkp@intel.com/config)
compiler: clang version 15.0.7 (https://github.com/llvm/llvm-project.git 8dfdcc7b7bf66834a761bd8de445840ef68e4d1a)
reproduce: (https://download.01.org/0day-ci/archive/20230628/202306282001.ba1qWTf0-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202306282001.ba1qWTf0-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/block/null_blk/main.c:1295:2: warning: variable 'rem' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           __rq_for_each_bio(bio, req) {
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/blk-mq.h:1012:6: note: expanded from macro '__rq_for_each_bio'
           if ((rq->bio))                  \
               ^~~~~~~~~
   drivers/block/null_blk/main.c:1300:15: note: uninitialized use occurs here
           if (WARN_ON(!rem))
                        ^~~
   include/asm-generic/bug.h:123:25: note: expanded from macro 'WARN_ON'
           int __ret_warn_on = !!(condition);                              \
                                  ^~~~~~~~~
   drivers/block/null_blk/main.c:1295:2: note: remove the 'if' if its condition is always true
           __rq_for_each_bio(bio, req) {
           ^
   include/linux/blk-mq.h:1012:2: note: expanded from macro '__rq_for_each_bio'
           if ((rq->bio))                  \
           ^
   drivers/block/null_blk/main.c:1287:12: note: initialize the variable 'rem' to silence this warning
           size_t rem, temp;
                     ^
                      = 0
   1 warning generated.


vim +1295 drivers/block/null_blk/main.c

  1281	
  1282	static inline int nullb_setup_copy_write(struct nullb *nullb,
  1283			struct request *req, bool is_fua)
  1284	{
  1285		sector_t sector_in, sector_out;
  1286		void *in, *out;
  1287		size_t rem, temp;
  1288		struct bio *bio;
  1289		unsigned long offset_in, offset_out;
  1290		struct nullb_page *t_page_in, *t_page_out;
  1291		int ret = -EIO;
  1292	
  1293		sector_out = blk_rq_pos(req);
  1294	
> 1295		__rq_for_each_bio(bio, req) {
  1296			sector_in = bio->bi_iter.bi_sector;
  1297			rem = bio->bi_iter.bi_size;
  1298		}
  1299	
  1300		if (WARN_ON(!rem))
  1301			return BLK_STS_NOTSUPP;
  1302	
  1303		spin_lock_irq(&nullb->lock);
  1304		while (rem > 0) {
  1305			temp = min_t(size_t, nullb->dev->blocksize, rem);
  1306			offset_in = (sector_in & SECTOR_MASK) << SECTOR_SHIFT;
  1307			offset_out = (sector_out & SECTOR_MASK) << SECTOR_SHIFT;
  1308	
  1309			if (null_cache_active(nullb) && !is_fua)
  1310				null_make_cache_space(nullb, PAGE_SIZE);
  1311	
  1312			t_page_in = null_lookup_page(nullb, sector_in, false,
  1313				!null_cache_active(nullb));
  1314			if (!t_page_in)
  1315				goto err;
  1316			t_page_out = null_insert_page(nullb, sector_out,
  1317				!null_cache_active(nullb) || is_fua);
  1318			if (!t_page_out)
  1319				goto err;
  1320	
  1321			in = kmap_local_page(t_page_in->page);
  1322			out = kmap_local_page(t_page_out->page);
  1323	
  1324			memcpy(out + offset_out, in + offset_in, temp);
  1325			kunmap_local(out);
  1326			kunmap_local(in);
  1327			__set_bit(sector_out & SECTOR_MASK, t_page_out->bitmap);
  1328	
  1329			if (is_fua)
  1330				null_free_sector(nullb, sector_out, true);
  1331	
  1332			rem -= temp;
  1333			sector_in += temp >> SECTOR_SHIFT;
  1334			sector_out += temp >> SECTOR_SHIFT;
  1335		}
  1336	
  1337		ret = 0;
  1338	err:
  1339		spin_unlock_irq(&nullb->lock);
  1340		return ret;
  1341	}
  1342
diff mbox series

Patch

diff --git a/Documentation/block/null_blk.rst b/Documentation/block/null_blk.rst
index 4dd78f24d10a..6153e02fcf13 100644
--- a/Documentation/block/null_blk.rst
+++ b/Documentation/block/null_blk.rst
@@ -149,3 +149,8 @@  zone_size=[MB]: Default: 256
 zone_nr_conv=[nr_conv]: Default: 0
   The number of conventional zones to create when block device is zoned.  If
   zone_nr_conv >= nr_zones, it will be reduced to nr_zones - 1.
+
+copy_max_bytes=[size in bytes]: Default: COPY_MAX_BYTES
+  A module and configfs parameter which can be used to set hardware/driver
+  supported maximum copy offload limit.
+  COPY_MAX_BYTES(=128MB at present) is defined in fs.h
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 864013019d6b..e9461bd4dc2c 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -157,6 +157,10 @@  static int g_max_sectors;
 module_param_named(max_sectors, g_max_sectors, int, 0444);
 MODULE_PARM_DESC(max_sectors, "Maximum size of a command (in 512B sectors)");
 
+static unsigned long g_copy_max_bytes = COPY_MAX_BYTES;
+module_param_named(copy_max_bytes, g_copy_max_bytes, ulong, 0444);
+MODULE_PARM_DESC(copy_max_bytes, "Maximum size of a copy command (in bytes)");
+
 static unsigned int nr_devices = 1;
 module_param(nr_devices, uint, 0444);
 MODULE_PARM_DESC(nr_devices, "Number of devices to register");
@@ -409,6 +413,7 @@  NULLB_DEVICE_ATTR(home_node, uint, NULL);
 NULLB_DEVICE_ATTR(queue_mode, uint, NULL);
 NULLB_DEVICE_ATTR(blocksize, uint, NULL);
 NULLB_DEVICE_ATTR(max_sectors, uint, NULL);
+NULLB_DEVICE_ATTR(copy_max_bytes, uint, NULL);
 NULLB_DEVICE_ATTR(irqmode, uint, NULL);
 NULLB_DEVICE_ATTR(hw_queue_depth, uint, NULL);
 NULLB_DEVICE_ATTR(index, uint, NULL);
@@ -550,6 +555,7 @@  static struct configfs_attribute *nullb_device_attrs[] = {
 	&nullb_device_attr_queue_mode,
 	&nullb_device_attr_blocksize,
 	&nullb_device_attr_max_sectors,
+	&nullb_device_attr_copy_max_bytes,
 	&nullb_device_attr_irqmode,
 	&nullb_device_attr_hw_queue_depth,
 	&nullb_device_attr_index,
@@ -656,7 +662,8 @@  static ssize_t memb_group_features_show(struct config_item *item, char *page)
 			"poll_queues,power,queue_mode,shared_tag_bitmap,size,"
 			"submit_queues,use_per_node_hctx,virt_boundary,zoned,"
 			"zone_capacity,zone_max_active,zone_max_open,"
-			"zone_nr_conv,zone_offline,zone_readonly,zone_size\n");
+			"zone_nr_conv,zone_offline,zone_readonly,zone_size,"
+			"copy_max_bytes\n");
 }
 
 CONFIGFS_ATTR_RO(memb_group_, features);
@@ -722,6 +729,7 @@  static struct nullb_device *null_alloc_dev(void)
 	dev->queue_mode = g_queue_mode;
 	dev->blocksize = g_bs;
 	dev->max_sectors = g_max_sectors;
+	dev->copy_max_bytes = g_copy_max_bytes;
 	dev->irqmode = g_irqmode;
 	dev->hw_queue_depth = g_hw_queue_depth;
 	dev->blocking = g_blocking;
@@ -1271,6 +1279,67 @@  static int null_transfer(struct nullb *nullb, struct page *page,
 	return err;
 }
 
+static inline int nullb_setup_copy_write(struct nullb *nullb,
+		struct request *req, bool is_fua)
+{
+	sector_t sector_in, sector_out;
+	void *in, *out;
+	size_t rem, temp;
+	struct bio *bio;
+	unsigned long offset_in, offset_out;
+	struct nullb_page *t_page_in, *t_page_out;
+	int ret = -EIO;
+
+	sector_out = blk_rq_pos(req);
+
+	__rq_for_each_bio(bio, req) {
+		sector_in = bio->bi_iter.bi_sector;
+		rem = bio->bi_iter.bi_size;
+	}
+
+	if (WARN_ON(!rem))
+		return BLK_STS_NOTSUPP;
+
+	spin_lock_irq(&nullb->lock);
+	while (rem > 0) {
+		temp = min_t(size_t, nullb->dev->blocksize, rem);
+		offset_in = (sector_in & SECTOR_MASK) << SECTOR_SHIFT;
+		offset_out = (sector_out & SECTOR_MASK) << SECTOR_SHIFT;
+
+		if (null_cache_active(nullb) && !is_fua)
+			null_make_cache_space(nullb, PAGE_SIZE);
+
+		t_page_in = null_lookup_page(nullb, sector_in, false,
+			!null_cache_active(nullb));
+		if (!t_page_in)
+			goto err;
+		t_page_out = null_insert_page(nullb, sector_out,
+			!null_cache_active(nullb) || is_fua);
+		if (!t_page_out)
+			goto err;
+
+		in = kmap_local_page(t_page_in->page);
+		out = kmap_local_page(t_page_out->page);
+
+		memcpy(out + offset_out, in + offset_in, temp);
+		kunmap_local(out);
+		kunmap_local(in);
+		__set_bit(sector_out & SECTOR_MASK, t_page_out->bitmap);
+
+		if (is_fua)
+			null_free_sector(nullb, sector_out, true);
+
+		rem -= temp;
+		sector_in += temp >> SECTOR_SHIFT;
+		sector_out += temp >> SECTOR_SHIFT;
+	}
+
+	ret = 0;
+err:
+	spin_unlock_irq(&nullb->lock);
+	return ret;
+}
+
 static int null_handle_rq(struct nullb_cmd *cmd)
 {
 	struct request *rq = cmd->rq;
@@ -1280,13 +1349,16 @@  static int null_handle_rq(struct nullb_cmd *cmd)
 	sector_t sector = blk_rq_pos(rq);
 	struct req_iterator iter;
 	struct bio_vec bvec;
+	bool fua = rq->cmd_flags & REQ_FUA;
+
+	if (op_is_copy(req_op(rq)))
+		return nullb_setup_copy_write(nullb, rq, fua);
 
 	spin_lock_irq(&nullb->lock);
 	rq_for_each_segment(bvec, rq, iter) {
 		len = bvec.bv_len;
 		err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
-				     op_is_write(req_op(rq)), sector,
-				     rq->cmd_flags & REQ_FUA);
+				     op_is_write(req_op(rq)), sector, fua);
 		if (err) {
 			spin_unlock_irq(&nullb->lock);
 			return err;
@@ -2042,6 +2114,9 @@  static int null_validate_conf(struct nullb_device *dev)
 		return -EINVAL;
 	}
 
+	if (dev->queue_mode == NULL_Q_BIO)
+		dev->copy_max_bytes = 0;
+
 	return 0;
 }
 
@@ -2161,6 +2236,10 @@  static int null_add_dev(struct nullb_device *dev)
 		dev->max_sectors = queue_max_hw_sectors(nullb->q);
 	dev->max_sectors = min(dev->max_sectors, BLK_DEF_MAX_SECTORS);
 	blk_queue_max_hw_sectors(nullb->q, dev->max_sectors);
+	blk_queue_max_copy_sectors_hw(nullb->q,
+			       dev->copy_max_bytes >> SECTOR_SHIFT);
+	if (dev->copy_max_bytes)
+		blk_queue_flag_set(QUEUE_FLAG_COPY, nullb->disk->queue);
 
 	if (dev->virt_boundary)
 		blk_queue_virt_boundary(nullb->q, PAGE_SIZE - 1);
diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index 929f659dd255..e82e53a2e2df 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -107,6 +107,7 @@  struct nullb_device {
 	unsigned int queue_mode; /* block interface */
 	unsigned int blocksize; /* block size */
 	unsigned int max_sectors; /* Max sectors per command */
+	unsigned long copy_max_bytes; /* Max copy offload length in bytes */
 	unsigned int irqmode; /* IRQ completion handler */
 	unsigned int hw_queue_depth; /* queue depth */
 	unsigned int index; /* index of the disk, only valid with a disk */