On Mon, 11 Apr 2016, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> copy_params seems to be little bit confused about which allocation flags
> to use. It enforces GFP_NOIO even though it uses
> memalloc_noio_{save,restore} which enforces GFP_NOIO at the page
memalloc_noio_{save,restore} is used because __vmalloc is flawed and
doesn't respect GFP_NOIO properly (it doesn't use gfp flags when
allocating pagetables).
The proper fix it to correct __vmalloc (though, it would require change to
pagetable allocation routine on all architectures), not to remove GFP_NOIO
from __vmalloc.
Mikulas
> allocator level automatically (via memalloc_noio_flags). It also
> uses __GFP_REPEAT for the __vmalloc request which doesn't make much
> sense either because vmalloc doesn't rely on costly high order
> allocations.
>
> Cc: Shaohua Li <shli@xxxxxxxxxx>
> Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> drivers/md/dm-ioctl.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index 2adf81d81fca..dfe629a294e1 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1723,7 +1723,7 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
> if (!dmi) {
> unsigned noio_flag;
> noio_flag = memalloc_noio_save();
> - dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
> + dmi = __vmalloc(param_kernel->data_size, __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
> memalloc_noio_restore(noio_flag);
> if (dmi)
> *param_flags |= DM_PARAMS_VMALLOC;
> --
> 2.8.0.rc3
>
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