On Mon, 30 Jan 2017, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> 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 <mpatocka@xxxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> 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.
Mikulas
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