On Wed 01-02-17 12:29:56, Mikulas Patocka wrote:
>
>
> On Mon, 30 Jan 2017, Michal Hocko wrote:
>
> > From: Michal Hocko <mho...@suse.com>
> >
> > copy_params uses kmalloc with vmalloc fallback. We already have a helper
> > for that - kvmalloc. This caller requires GFP_NOIO semantic so it hasn't
> > been converted with many others by previous patches. All we need to
> > achieve this semantic is to use the scope memalloc_noio_{save,restore}
> > around kvmalloc.
> >
> > Cc: Mikulas Patocka <mpato...@redhat.com>
> > Cc: Mike Snitzer <snit...@redhat.com>
> > Signed-off-by: Michal Hocko <mho...@suse.com>
> > ---
> > drivers/md/dm-ioctl.c | 13 ++++---------
> > 1 file changed, 4 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > index a5a9b17f0f7f..dbf5b981f7d7 100644
> > --- a/drivers/md/dm-ioctl.c
> > +++ b/drivers/md/dm-ioctl.c
> > @@ -1698,6 +1698,7 @@ static int copy_params(struct dm_ioctl __user *user,
> > struct dm_ioctl *param_kern
> > struct dm_ioctl *dmi;
> > int secure_data;
> > const size_t minimum_data_size = offsetof(struct dm_ioctl, data);
> > + unsigned noio_flag;
> >
> > if (copy_from_user(param_kernel, user, minimum_data_size))
> > return -EFAULT;
> > @@ -1720,15 +1721,9 @@ static int copy_params(struct dm_ioctl __user *user,
> > struct dm_ioctl *param_kern
> > * Use kmalloc() rather than vmalloc() when we can.
> > */
> > dmi = NULL;
> > - if (param_kernel->data_size <= KMALLOC_MAX_SIZE)
> > - dmi = kmalloc(param_kernel->data_size, GFP_NOIO | __GFP_NORETRY
> > | __GFP_NOMEMALLOC | __GFP_NOWARN);
> > -
> > - if (!dmi) {
> > - unsigned noio_flag;
> > - noio_flag = memalloc_noio_save();
> > - dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_HIGH
> > | __GFP_HIGHMEM, PAGE_KERNEL);
> > - memalloc_noio_restore(noio_flag);
> > - }
> > + noio_flag = memalloc_noio_save();
> > + dmi = kvmalloc(param_kernel->data_size, GFP_KERNEL);
> > + memalloc_noio_restore(noio_flag);
> >
> > if (!dmi) {
> > if (secure_data && clear_user(user, param_kernel->data_size))
> > --
> > 2.11.0
>
> I would push these memalloc_noio_save/memalloc_noio_restore calls to
> kvmalloc, so that the othe callers can use them too.
>
> Something like
> if ((flags & (__GFP_IO | __GFP_FS)) != (__GFP_IO | __GFP_FS))
> noio_flag = memalloc_noio_save();
> ptr = __vmalloc_node_flags(size, node, flags);
> if ((flags & (__GFP_IO | __GFP_FS)) != (__GFP_IO | __GFP_FS))
> memalloc_noio_restore(noio_flag)
>
> Or perhaps even better - push memalloc_noio_save/memalloc_noio_restore
> directly to __vmalloc, so that __vmalloc respects the gfp flags properly -
> note that there are 14 places in the kernel where __vmalloc is called with
> GFP_NOFS and they are all buggy because __vmalloc doesn't respect the
> GFP_NOFS flag.
That is out of scope of this patch series. I would like to deal with
NOIO an NOFS contexts separately.
--
Michal Hocko
SUSE Labs
