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xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing 

Commit 9c17d96500 ("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>
This commit is contained in:
Boris Ostrovsky 2016-11-21 09:56:06 -05:00 committed by Juergen Gross
parent 1eb08545c0
commit 30faaafdfa
1 changed files with 1 additions and 1 deletions
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2
drivers/xen/gntdev.c
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@ -1007,7 +1007,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
vma->vm_ops = &gntdev_vmops;
vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_IO;
vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_MIXEDMAP;
if (use_ptemod)
vma->vm_flags |= VM_DONTCOPY;