diff options
| author | David Vrabel <david.vrabel@citrix.com> | 2011-09-14 16:22:02 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-10-03 11:40:30 -0700 |
| commit | d63c8a029e509ad48ee9290874731789f9008537 (patch) | |
| tree | 0a7c79f56bbc8a624d09486cdc88c5a7d1f872ae /mm | |
| parent | 97abc52eb26f2ae8d033100c4c024e6138bdfd60 (diff) | |
mm: sync vmalloc address space page tables in alloc_vm_area()
commit 461ae488ecb125b140d7ea29ceeedbcce9327003 upstream.
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 <david.vrabel@citrix.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
Cc: Keir Fraser <keir.xen@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmalloc.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index d3d451bcdf2d..45ece8967e47 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2154,6 +2154,14 @@ 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; } EXPORT_SYMBOL_GPL(alloc_vm_area); |