Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.8 79/85] xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing | Date | Wed, 4 Jan 2017 21:48:04 +0100 |
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4.8-stable review patch. If anyone has any objections, please let me know.
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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
commit 30faaafdfa0c754c91bac60f216c9f34a2bfdf7e upstream.
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().
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/xen/gntdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -1007,7 +1007,7 @@ static int gntdev_mmap(struct file *flip 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;
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