[Xen-devel] [PATCH 6/6] mm: remove vmalloc_sync_all() from alloc_vm_area()

[David Vrabel <david.vrabel@xxxxxxxxxx>]

From: David Vrabel <david.vrabel@xxxxxxxxxx>

The address space allocated by the remaining user of alloc_vm_area()
is not accessed during a hypercall.  Therefore, the normal mechanism
of populating the vmalloc page tables during a fault works so the
vmalloc_sync_all() is not required and it can be removed.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 mm/vmalloc.c |   12 +-----------
 1 files changed, 1 insertions(+), 11 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5016f19..b0b4550 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2117,9 +2117,7 @@ static int f(pte_t *pte, pgtable_t table, unsigned long 
addr, void *data)
  *
  *     This function reserves a range of kernel address space, and
  *     allocates pagetables to map that range.  No actual mappings
- *     are created.  If the kernel address space is not shared
- *     between processes, it syncs the pagetable across all
- *     processes.
+ *     are created.
  */
 struct vm_struct *alloc_vm_area(size_t size)
 {
@@ -2140,14 +2138,6 @@ struct vm_struct *alloc_vm_area(size_t size)
                return NULL;
        }
 
-       /*
-        * If the allocated address space is passed to a hypercall
-        * before being used then we cannot rely on a page fault to
-        * trigger an update of the page tables.  So sync all the page
-        * tables here.
-        */
-       vmalloc_sync_all();
-
        return area;
 }
 EXPORT_SYMBOL_GPL(alloc_vm_area);
-- 
1.7.2.5


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