> From: Michal Hocko <mhocko@xxxxxxxx>
>
> Dave Chinner has mentioned that some of the xfs code would benefit from
> kvmalloc support for __GFP_NOFAIL because they have allocations that
> cannot fail and they do not fit into a single page.
>
> The larg part of the vmalloc implementation already complies with the
> given gfp flags so there is no work for those to be done. The area
> and page table allocations are an exception to that. Implement a retry
> loop for those.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/vmalloc.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 7455c89598d3..3a5a178295d1 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2941,8 +2941,10 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> else if (!(gfp_mask & (__GFP_FS | __GFP_IO)))
> flags = memalloc_noio_save();
>
> - ret = vmap_pages_range(addr, addr + size, prot, area->pages,
> + do {
> + ret = vmap_pages_range(addr, addr + size, prot, area->pages,
> page_shift);
> + } while ((gfp_mask & __GFP_NOFAIL) && (ret < 0));
>
> if ((gfp_mask & (__GFP_FS | __GFP_IO)) == __GFP_IO)
> memalloc_nofs_restore(flags);
> @@ -3032,6 +3034,8 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
> warn_alloc(gfp_mask, NULL,
> "vmalloc error: size %lu, vm_struct allocation failed",
> real_size);
> + if (gfp_mask && __GFP_NOFAIL)
> + goto again;
> goto fail;
> }
>
> --
> 2.30.2
>
I have checked the vmap code how it aligns with the __GFP_NOFAIL flag.
To me it looks correct from functional point of view.
There is one place though it is kasan_populate_vmalloc_pte(). It does
not use gfp_mask, instead it directly deals with GFP_KERNEL for its
internal purpose. If it fails the code will end up in loping in the
__vmalloc_node_range().
I am not sure how it is important to pass __GFP_NOFAIL into KASAN code.
Any thoughts about it?
--
Vlad Rezki
