xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing
authorBoris Ostrovsky <boris.ostrovsky@oracle.com>
Mon, 21 Nov 2016 14:56:06 +0000 (09:56 -0500)
committerJuergen Gross <jgross@suse.com>
Mon, 28 Nov 2016 13:14:05 +0000 (14:14 +0100)
commit30faaafdfa0c754c91bac60f216c9f34a2bfdf7e
tree2a498846f2fa8e0f62016df566cc0f33afbebae2
parent1eb08545c0a3a2249ad53e393383cc06163d0d16
xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing

Commit 9c17d96500f7 ("xen/gntdev: Grant maps should not be subject to
NUMA balancing") set VM_IO flag to prevent grant maps from being
subjected to NUMA balancing.

It was discovered recently that this flag causes get_user_pages() to
always fail with -EFAULT.

check_vma_flags
__get_user_pages
__get_user_pages_locked
__get_user_pages_unlocked
get_user_pages_fast
iov_iter_get_pages
dio_refill_pages
do_direct_IO
do_blockdev_direct_IO
do_blockdev_direct_IO
ext4_direct_IO_read
generic_file_read_iter
aio_run_iocb

(which can happen if guest's vdisk has direct-io-safe option).

To avoid this let's use VM_MIXEDMAP flag instead --- it prevents
NUMA balancing just as VM_IO does and has no effect on
check_vma_flags().

Cc: stable@vger.kernel.org
Reported-by: Olaf Hering <olaf@aepfle.de>
Suggested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Hugh Dickins <hughd@google.com>
Tested-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Juergen Gross <jgross@suse.com>
drivers/xen/gntdev.c