Re: [PATCH v4] xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing
On 21/11/16 15:56, Boris Ostrovsky wrote: > 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 > Suggested-by: Hugh Dickins > Signed-off-by: Boris Ostrovsky Applied to xen/tip.git for-linus-4.10 Juergen > --- > drivers/xen/gntdev.c |2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index bb95212..2ef2b61 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -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; >
Re: [PATCH v4] xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing
On Mon, Nov 21, Boris Ostrovsky wrote: > 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. Tested-by: Olaf Hering This should go to stable as well. Olaf signature.asc Description: PGP signature
Re: [PATCH v4] xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing
On 22/11/16 04:59, Hugh Dickins wrote: > On Mon, 21 Nov 2016, Boris Ostrovsky wrote: > >> 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 >> Suggested-by: Hugh Dickins >> Signed-off-by: Boris Ostrovsky > > Acked-by: Hugh Dickins > > But nicer with the addition of a code comment saying > /* VM_MIXEDMAP to forbid NUMA balancing but permit get_user_pages() */ I can fix that up when committing. Juergen > >> --- >> drivers/xen/gntdev.c |2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c >> index bb95212..2ef2b61 100644 >> --- a/drivers/xen/gntdev.c >> +++ b/drivers/xen/gntdev.c >> @@ -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; >> -- >> 1.7.1 >
Re: [PATCH v4] xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing
On Mon, 21 Nov 2016, Boris Ostrovsky wrote: > 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 > Suggested-by: Hugh Dickins > Signed-off-by: Boris Ostrovsky Acked-by: Hugh Dickins But nicer with the addition of a code comment saying /* VM_MIXEDMAP to forbid NUMA balancing but permit get_user_pages() */ > --- > drivers/xen/gntdev.c |2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index bb95212..2ef2b61 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -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; > -- > 1.7.1
[PATCH v4] 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(). Reported-by: Olaf Hering Suggested-by: Hugh Dickins Signed-off-by: Boris Ostrovsky --- drivers/xen/gntdev.c |2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index bb95212..2ef2b61 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -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; -- 1.7.1