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