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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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@xxxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
>     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@xxxxxxxxxxxxx>

>  {
>       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
>

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