Re: [PATCH v9 9/9] null_blk: add support for copy offload

[Chaitanya Kulkarni <chaitanyak@nvidia.com>]

On 4/11/23 01:10, Anuj Gupta wrote:
> From: Nitesh Shetty <nj.shetty@samsung.com>
>
> 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>
> ---
>   drivers/block/null_blk/main.c     | 101 ++++++++++++++++++++++++++++++
>   drivers/block/null_blk/null_blk.h |   8 +++
>   2 files changed, 109 insertions(+)
>
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index bc2c58724df3..e273e18ace74 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 int g_copy_max_bytes = COPY_MAX_BYTES;

how about following ? matches nullb_device->copy_max_bytes type ..

-static int g_copy_max_bytes = COPY_MAX_BYTES;
-module_param_named(copy_max_bytes, g_copy_max_bytes, int, 0444);
+static unsigned long g_copy_max_bytes = COPY_MAX_BYTES;
+module_param_named(copy_max_bytes, g_copy_max_bytes, ulong, 0444);

[...]

> @@ -631,6 +637,7 @@ static ssize_t memb_group_features_show(struct config_item *item, char *page)
>   			"badblocks,blocking,blocksize,cache_size,"
>   			"completion_nsec,discard,home_node,hw_queue_depth,"
>   			"irqmode,max_sectors,mbps,memory_backed,no_sched,"
> +			"copy_max_bytes,"
>   			"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,"

why not ?

@@ -637,11 +637,12 @@ static ssize_t memb_group_features_show(struct config_item *item, char *page)
                         "badblocks,blocking,blocksize,cache_size,"
                         "completion_nsec,discard,home_node,hw_queue_depth,"
                         "irqmode,max_sectors,mbps,memory_backed,no_sched,"
-                       "copy_max_bytes,"
                         "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");
  }
  
[...]
  
+static inline int nullb_setup_copy_read(struct nullb *nullb,
+		struct bio *bio)
+{
+	struct nullb_copy_token *token = bvec_kmap_local(&bio->bi_io_vec[0]);
+
+	memcpy(token->subsys, "nullb", 5);

do you really need to use memcpy here ? can token->subsys be a pointer
and use with assignment token->subsys = nullb ?

+	token->sector_in = bio->bi_iter.bi_sector;
+	token->nullb = nullb;
+	token->sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT;
+
+	return 0;
+}
+

no point in return 0 , use local bool for fua instead of repeating
expression and no need to fold line for nullb_setup_copy_read()
makes is easy to read and removes extra lines and indentation see below :-

-static inline int nullb_setup_copy_read(struct nullb *nullb,
-               struct bio *bio)
+static inline void nullb_setup_copy_read(struct nullb *nullb, struct bio *bio)
  {
         struct nullb_copy_token *token = bvec_kmap_local(&bio->bi_io_vec[0]);
  
-       memcpy(token->subsys, "nullb", 5);
+       token->subsys = "nullb;
         token->sector_in = bio->bi_iter.bi_sector;
         token->nullb = nullb;
         token->sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT;
-
-       return 0;
  }
  
  static inline int nullb_setup_copy_write(struct nullb *nullb,
@@ -1334,20 +1331,21 @@ 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 (rq->cmd_flags & REQ_COPY) {
                 if (op_is_write(req_op(rq)))
-                       return nullb_setup_copy_write(nullb, rq->bio,
-                                               rq->cmd_flags & REQ_FUA);
-               return nullb_setup_copy_read(nullb, rq->bio);
+                       return nullb_setup_copy_write(nullb, rq->bio, fua);
+
+               nullb_setup_copy_read(nullb, rq->bio);
+               return 0;
         }
  
         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;
@@ -1368,12 +1366,13 @@ static int null_handle_bio(struct nullb_cmd *cmd)
         sector_t sector = bio->bi_iter.bi_sector;
         struct bio_vec bvec;
         struct bvec_iter iter;
+       bool fua = bio->bi_opf & REQ_FUA
  
         if (bio->bi_opf & REQ_COPY) {
                 if (op_is_write(bio_op(bio)))
-                       return nullb_setup_copy_write(nullb, bio,
-                                                       bio->bi_opf & REQ_FUA);
-               return nullb_setup_copy_read(nullb, bio);
+                       return nullb_setup_copy_write(nullb, bio, fua);
+               nullb_setup_copy_read(nullb, bio);
+               return 0;
         }
  



[...]
  
+struct nullb_copy_token {
+	char subsys[5];
+	struct nullb *nullb;
+	u64 sector_in;
+	u64 sectors;
+};
+

why not use sector_t ?

diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index c67c098d92fa..ffa4b6a6d19b 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -70,8 +70,8 @@ enum {
  struct nullb_copy_token {
         char subsys[5];
         struct nullb *nullb;
-       u64 sector_in;
-       u64 sectors;
+       sector_t sector_in;
+       sector_t sectors;
  };
  

-ck