[Xen-devel] [PATCH 1/3] gnttab: Drop the frame parameter from acquire_grant_for_copy()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

It is redundant with the *page parameter.  Rename the grant_frame parameter to
indicate that it is local, and highlight the correctness of the change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/common/grant_table.c | 42 ++++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 36895aa..188c477 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -2142,15 +2142,17 @@ static void fixup_status_for_copy_pin(const struct 
active_grant_entry *act,
         gnttab_clear_flag(_GTF_reading, status);
 }
 
-/* Grab a frame number from a grant entry and update the flags and pin
-   count as appropriate. If rc == GNTST_okay, note that this *does*
-   take one ref count on the target page, stored in *page.
-   If there is any error, *page = NULL, no ref taken. */
+/*
+ * Grab a frame number from a grant entry and update the flags and pin
+ * count as appropriate. If rc == GNTST_okay, note that this *does*
+ * take one ref count on the target page, stored in *page.
+ * If there is any error, *page = NULL, no ref taken.
+ */
 static int
 acquire_grant_for_copy(
     struct domain *rd, grant_ref_t gref, domid_t ldom, bool readonly,
-    unsigned long *frame, struct page_info **page,
-    uint16_t *page_off, uint16_t *length, bool allow_transitive)
+    struct page_info **page, uint16_t *page_off, uint16_t *length,
+    bool allow_transitive)
 {
     struct grant_table *rgt = rd->grant_table;
     grant_entry_v2_t *sha2;
@@ -2161,7 +2163,7 @@ acquire_grant_for_copy(
     domid_t trans_domid;
     grant_ref_t trans_gref;
     struct domain *td;
-    unsigned long grant_frame;
+    unsigned long frame;
     uint16_t trans_page_off;
     uint16_t trans_length;
     bool is_sub_page;
@@ -2238,10 +2240,9 @@ acquire_grant_for_copy(
         active_entry_release(act);
         grant_read_unlock(rgt);
 
-        rc = acquire_grant_for_copy(td, trans_gref, rd->domain_id,
-                                    readonly, &grant_frame, page,
-                                    &trans_page_off, &trans_length,
-                                    false);
+        rc = acquire_grant_for_copy(
+            td, trans_gref, rd->domain_id, readonly, page, &trans_page_off,
+            &trans_length, false);
 
         grant_read_lock(rgt);
         act = active_entry_acquire(rgt, gref);
@@ -2255,6 +2256,8 @@ acquire_grant_for_copy(
             return rc;
         }
 
+        frame = page_to_mfn(*page);
+
         /*
          * We dropped the lock, so we have to check that the grant didn't
          * change, and that nobody else tried to pin/unpin it. If anything
@@ -2262,7 +2265,7 @@ acquire_grant_for_copy(
          */
         if ( rgt->gt_version != 2 ||
              act->pin != old_pin ||
-             (old_pin && (act->domid != ldom || act->frame != grant_frame ||
+             (old_pin && (act->domid != ldom || act->frame != frame ||
                           act->start != trans_page_off ||
                           act->length != trans_length ||
                           act->trans_domain != td ||
@@ -2286,7 +2289,7 @@ acquire_grant_for_copy(
             act->length = trans_length;
             act->trans_domain = td;
             act->trans_gref = trans_gref;
-            act->frame = grant_frame;
+            act->frame = frame;
             act_set_gfn(act, INVALID_GFN);
             /*
              * The actual remote remote grant may or may not be a sub-page,
@@ -2310,7 +2313,7 @@ acquire_grant_for_copy(
         {
             unsigned long gfn = shared_entry_v1(rgt, gref).frame;
 
-            rc = get_paged_frame(gfn, &grant_frame, page, readonly, rd);
+            rc = get_paged_frame(gfn, &frame, page, readonly, rd);
             if ( rc != GNTST_okay )
                 goto unlock_out_clear;
             act_set_gfn(act, _gfn(gfn));
@@ -2320,7 +2323,7 @@ acquire_grant_for_copy(
         }
         else if ( !(sha2->hdr.flags & GTF_sub_page) )
         {
-            rc = get_paged_frame(sha2->full_page.frame, &grant_frame, page,
+            rc = get_paged_frame(sha2->full_page.frame, &frame, page,
                                  readonly, rd);
             if ( rc != GNTST_okay )
                 goto unlock_out_clear;
@@ -2331,7 +2334,7 @@ acquire_grant_for_copy(
         }
         else
         {
-            rc = get_paged_frame(sha2->sub_page.frame, &grant_frame, page,
+            rc = get_paged_frame(sha2->sub_page.frame, &frame, page,
                                  readonly, rd);
             if ( rc != GNTST_okay )
                 goto unlock_out_clear;
@@ -2349,7 +2352,7 @@ acquire_grant_for_copy(
             act->length = trans_length;
             act->trans_domain = td;
             act->trans_gref = trans_gref;
-            act->frame = grant_frame;
+            act->frame = frame;
         }
     }
     else
@@ -2368,7 +2371,6 @@ acquire_grant_for_copy(
 
     *page_off = act->start;
     *length = act->length;
-    *frame = act->frame;
 
     active_entry_release(act);
     grant_read_unlock(rgt);
@@ -2503,11 +2505,11 @@ static int gnttab_copy_claim_buf(const struct 
gnttab_copy *op,
     {
         rc = acquire_grant_for_copy(buf->domain, ptr->u.ref,
                                     current->domain->domain_id,
-                                    buf->read_only,
-                                    &buf->frame, &buf->page,
+                                    buf->read_only, &buf->page,
                                     &buf->ptr.offset, &buf->len, true);
         if ( rc != GNTST_okay )
             goto out;
+        buf->frame = page_to_mfn(buf->page);
         buf->ptr.u.ref = ptr->u.ref;
         buf->have_grant = 1;
     }
-- 
2.1.4


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