path: root/mm
diff options
authorDavid Vrabel <>2011-09-14 16:22:02 -0700
committerLinus Torvalds <>2011-09-14 18:09:38 -0700
commit461ae488ecb125b140d7ea29ceeedbcce9327003 (patch)
tree165b09655495312068acfc7c0bc91df409c9c2ff /mm
parent185efc0f9a1f2d6ad6d4782c5d9e529f3290567f (diff)
mm: sync vmalloc address space page tables in alloc_vm_area()
Xen backend drivers (e.g., blkback and netback) would sometimes fail to map grant pages into the vmalloc address space allocated with alloc_vm_area(). The GNTTABOP_map_grant_ref would fail because Xen could not find the page (in the L2 table) containing the PTEs it needed to update. (XEN) mm.c:3846:d0 Could not find L1 PTE for address fbb42000 netback and blkback were making the hypercall from a kernel thread where task->active_mm != &init_mm and alloc_vm_area() was only updating the page tables for init_mm. The usual method of deferring the update to the page tables of other processes (i.e., after taking a fault) doesn't work as a fault cannot occur during the hypercall. This would work on some systems depending on what else was using vmalloc. Fix this by reverting ef691947d8a3 ("vmalloc: remove vmalloc_sync_all() from alloc_vm_area()") and add a comment to explain why it's needed. Signed-off-by: David Vrabel <> Cc: Jeremy Fitzhardinge <> Cc: Konrad Rzeszutek Wilk <> Cc: Ian Campbell <> Cc: Keir Fraser <> Cc: <> [3.0.x] Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm')
1 files changed, 8 insertions, 0 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 7ef0903058ee..5016f19e1661 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2140,6 +2140,14 @@ 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;