Re: [PATCH v2 06/20] block/xen-blkfront: Store a page rather a pfn in the grant structure

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

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On Thu, 9 Jul 2015, Julien Grall wrote:
> All the usage of the field pfn are done using the same idiom:
> 
> pfn_to_page(grant->pfn)
> 
> This will  return always the same page. Store directly the page in the
> grant to clean up the code.
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Roger Pau Monné <roger.pau@citrix.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> ---
>     Changes in v2:
>         - Patch added
> ---
>  drivers/block/xen-blkfront.c | 37 ++++++++++++++++++-------------------
>  1 file changed, 18 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 7107d58..7b81d23 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -67,7 +67,7 @@ enum blkif_state {
>  
>  struct grant {
>  	grant_ref_t gref;
> -	unsigned long pfn;
> +	struct page *page;
>  	struct list_head node;
>  };
>  
> @@ -219,7 +219,7 @@ static int fill_grant_buffer(struct blkfront_info *info, int num)
>  				kfree(gnt_list_entry);
>  				goto out_of_memory;
>  			}
> -			gnt_list_entry->pfn = page_to_pfn(granted_page);
> +			gnt_list_entry->page = granted_page;
>  		}
>  
>  		gnt_list_entry->gref = GRANT_INVALID_REF;
> @@ -234,7 +234,7 @@ out_of_memory:
>  	                         &info->grants, node) {
>  		list_del(&gnt_list_entry->node);
>  		if (info->feature_persistent)
> -			__free_page(pfn_to_page(gnt_list_entry->pfn));
> +			__free_page(gnt_list_entry->page);
>  		kfree(gnt_list_entry);
>  		i--;
>  	}
> @@ -243,7 +243,7 @@ out_of_memory:
>  }
>  
>  static struct grant *get_grant(grant_ref_t *gref_head,
> -                               unsigned long pfn,
> +			       struct page *page,
>                                 struct blkfront_info *info)

indentation

Aside from this:

Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

>  {
>  	struct grant *gnt_list_entry;
> @@ -263,10 +263,10 @@ static struct grant *get_grant(grant_ref_t *gref_head,
>  	gnt_list_entry->gref = gnttab_claim_grant_reference(gref_head);
>  	BUG_ON(gnt_list_entry->gref == -ENOSPC);
>  	if (!info->feature_persistent) {
> -		BUG_ON(!pfn);
> -		gnt_list_entry->pfn = pfn;
> +		BUG_ON(!page);
> +		gnt_list_entry->page = page;
>  	}
> -	buffer_mfn = pfn_to_mfn(gnt_list_entry->pfn);
> +	buffer_mfn = page_to_mfn(gnt_list_entry->page);
>  	gnttab_grant_foreign_access_ref(gnt_list_entry->gref,
>  	                                info->xbdev->otherend_id,
>  	                                buffer_mfn, 0);
> @@ -522,7 +522,7 @@ static int blkif_queue_rw_req(struct request *req)
>  
>  		if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
>  		    (i % SEGS_PER_INDIRECT_FRAME == 0)) {
> -			unsigned long uninitialized_var(pfn);
> +			struct page *uninitialized_var(page);
>  
>  			if (segments)
>  				kunmap_atomic(segments);
> @@ -536,15 +536,15 @@ static int blkif_queue_rw_req(struct request *req)
>  				indirect_page = list_first_entry(&info->indirect_pages,
>  				                                 struct page, lru);
>  				list_del(&indirect_page->lru);
> -				pfn = page_to_pfn(indirect_page);
> +				page = indirect_page;
>  			}
> -			gnt_list_entry = get_grant(&gref_head, pfn, info);
> +			gnt_list_entry = get_grant(&gref_head, page, info);
>  			info->shadow[id].indirect_grants[n] = gnt_list_entry;
> -			segments = kmap_atomic(pfn_to_page(gnt_list_entry->pfn));
> +			segments = kmap_atomic(gnt_list_entry->page);
>  			ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
>  		}
>  
> -		gnt_list_entry = get_grant(&gref_head, page_to_pfn(sg_page(sg)), info);
> +		gnt_list_entry = get_grant(&gref_head, sg_page(sg), info);
>  		ref = gnt_list_entry->gref;
>  
>  		info->shadow[id].grants_used[i] = gnt_list_entry;
> @@ -555,7 +555,7 @@ static int blkif_queue_rw_req(struct request *req)
>  
>  			BUG_ON(sg->offset + sg->length > PAGE_SIZE);
>  
> -			shared_data = kmap_atomic(pfn_to_page(gnt_list_entry->pfn));
> +			shared_data = kmap_atomic(gnt_list_entry->page);
>  			bvec_data = kmap_atomic(sg_page(sg));
>  
>  			/*
> @@ -1002,7 +1002,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
>  				info->persistent_gnts_c--;
>  			}
>  			if (info->feature_persistent)
> -				__free_page(pfn_to_page(persistent_gnt->pfn));
> +				__free_page(persistent_gnt->page);
>  			kfree(persistent_gnt);
>  		}
>  	}
> @@ -1037,7 +1037,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
>  			persistent_gnt = info->shadow[i].grants_used[j];
>  			gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
>  			if (info->feature_persistent)
> -				__free_page(pfn_to_page(persistent_gnt->pfn));
> +				__free_page(persistent_gnt->page);
>  			kfree(persistent_gnt);
>  		}
>  
> @@ -1051,7 +1051,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
>  		for (j = 0; j < INDIRECT_GREFS(segs); j++) {
>  			persistent_gnt = info->shadow[i].indirect_grants[j];
>  			gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
> -			__free_page(pfn_to_page(persistent_gnt->pfn));
> +			__free_page(persistent_gnt->page);
>  			kfree(persistent_gnt);
>  		}
>  
> @@ -1102,8 +1102,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
>  	if (bret->operation == BLKIF_OP_READ && info->feature_persistent) {
>  		for_each_sg(s->sg, sg, nseg, i) {
>  			BUG_ON(sg->offset + sg->length > PAGE_SIZE);
> -			shared_data = kmap_atomic(
> -				pfn_to_page(s->grants_used[i]->pfn));
> +			shared_data = kmap_atomic(s->grants_used[i]->page);
>  			bvec_data = kmap_atomic(sg_page(sg));
>  			memcpy(bvec_data   + sg->offset,
>  			       shared_data + sg->offset,
> @@ -1154,7 +1153,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
>  				 * Add the used indirect page back to the list of
>  				 * available pages for indirect grefs.
>  				 */
> -				indirect_page = pfn_to_page(s->indirect_grants[i]->pfn);
> +				indirect_page = s->indirect_grants[i]->page;
>  				list_add(&indirect_page->lru, &info->indirect_pages);
>  				s->indirect_grants[i]->gref = GRANT_INVALID_REF;
>  				list_add_tail(&s->indirect_grants[i]->node, &info->grants);
> -- 
> 2.1.4
>