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[PATCH 3/9] gnttab: fold recurring is_iomem_page()

  • To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 26 Aug 2021 12:12:28 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
  • Delivery-date: Thu, 26 Aug 2021 10:12:37 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
In all cases call the function just once instead of up to four times, at
the same time avoiding to store a dangling pointer in a local variable.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -1587,11 +1587,11 @@ unmap_common_complete(struct gnttab_unma
     else
         status = &status_entry(rgt, op->ref);
 
-    pg = mfn_to_page(op->mfn);
+    pg = !is_iomem_page(act->mfn) ? mfn_to_page(op->mfn) : NULL;
 
     if ( op->done & GNTMAP_device_map )
     {
-        if ( !is_iomem_page(act->mfn) )
+        if ( pg )
         {
             if ( op->done & GNTMAP_readonly )
                 put_page(pg);
@@ -1608,7 +1608,7 @@ unmap_common_complete(struct gnttab_unma
 
     if ( op->done & GNTMAP_host_map )
     {
-        if ( !is_iomem_page(op->mfn) )
+        if ( pg )
         {
             if ( gnttab_host_mapping_get_page_type(op->done & GNTMAP_readonly,
                                                    ld, rd) )
@@ -3778,7 +3778,7 @@ int gnttab_release_mappings(struct domai
         else
             status = &status_entry(rgt, ref);
 
-        pg = mfn_to_page(act->mfn);
+        pg = !is_iomem_page(act->mfn) ? mfn_to_page(act->mfn) : NULL;
 
         if ( map->flags & GNTMAP_readonly )
         {
@@ -3786,7 +3786,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_devr_mask));
                 act->pin -= GNTPIN_devr_inc;
-                if ( !is_iomem_page(act->mfn) )
+                if ( pg )
                     put_page(pg);
             }
 
@@ -3794,8 +3794,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_hstr_mask));
                 act->pin -= GNTPIN_hstr_inc;
-                if ( gnttab_release_host_mappings(d) &&
-                     !is_iomem_page(act->mfn) )
+                if ( pg && gnttab_release_host_mappings(d) )
                     put_page(pg);
             }
         }
@@ -3805,7 +3804,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_devw_mask));
                 act->pin -= GNTPIN_devw_inc;
-                if ( !is_iomem_page(act->mfn) )
+                if ( pg )
                     put_page_and_type(pg);
             }
 
@@ -3813,8 +3812,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_hstw_mask));
                 act->pin -= GNTPIN_hstw_inc;
-                if ( gnttab_release_host_mappings(d) &&
-                     !is_iomem_page(act->mfn) )
+                if ( pg && gnttab_release_host_mappings(d) )
                 {
                     if ( gnttab_host_mapping_get_page_type(false, d, rd) )
                         put_page_type(pg);
In all cases call the function just once instead of up to four times, at
the same time avoiding to store a dangling pointer in a local variable.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -1587,11 +1587,11 @@ unmap_common_complete(struct gnttab_unma
     else
         status = &status_entry(rgt, op->ref);
 
-    pg = mfn_to_page(op->mfn);
+    pg = !is_iomem_page(act->mfn) ? mfn_to_page(op->mfn) : NULL;
 
     if ( op->done & GNTMAP_device_map )
     {
-        if ( !is_iomem_page(act->mfn) )
+        if ( pg )
         {
             if ( op->done & GNTMAP_readonly )
                 put_page(pg);
@@ -1608,7 +1608,7 @@ unmap_common_complete(struct gnttab_unma
 
     if ( op->done & GNTMAP_host_map )
     {
-        if ( !is_iomem_page(op->mfn) )
+        if ( pg )
         {
             if ( gnttab_host_mapping_get_page_type(op->done & GNTMAP_readonly,
                                                    ld, rd) )
@@ -3778,7 +3778,7 @@ int gnttab_release_mappings(struct domai
         else
             status = &status_entry(rgt, ref);
 
-        pg = mfn_to_page(act->mfn);
+        pg = !is_iomem_page(act->mfn) ? mfn_to_page(act->mfn) : NULL;
 
         if ( map->flags & GNTMAP_readonly )
         {
@@ -3786,7 +3786,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_devr_mask));
                 act->pin -= GNTPIN_devr_inc;
-                if ( !is_iomem_page(act->mfn) )
+                if ( pg )
                     put_page(pg);
             }
 
@@ -3794,8 +3794,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_hstr_mask));
                 act->pin -= GNTPIN_hstr_inc;
-                if ( gnttab_release_host_mappings(d) &&
-                     !is_iomem_page(act->mfn) )
+                if ( pg && gnttab_release_host_mappings(d) )
                     put_page(pg);
             }
         }
@@ -3805,7 +3804,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_devw_mask));
                 act->pin -= GNTPIN_devw_inc;
-                if ( !is_iomem_page(act->mfn) )
+                if ( pg )
                     put_page_and_type(pg);
             }
 
@@ -3813,8 +3812,7 @@ int gnttab_release_mappings(struct domai
             {
                 BUG_ON(!(act->pin & GNTPIN_hstw_mask));
                 act->pin -= GNTPIN_hstw_inc;
-                if ( gnttab_release_host_mappings(d) &&
-                     !is_iomem_page(act->mfn) )
+                if ( pg && gnttab_release_host_mappings(d) )
                 {
                     if ( gnttab_host_mapping_get_page_type(false, d, rd) )
                         put_page_type(pg);

 

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