> 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.
>
> Add a short sleep before retrying. 1 jiffy is a completely random
> timeout. Ideally the retry would wait for an explicit event - e.g.
> a change to the vmalloc space change if the failure was caused by
> the space fragmentation or depletion. But there are multiple different
> reasons to retry and this could become much more complex. Keep the retry
> simple for now and just sleep to prevent from hogging CPUs.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/vmalloc.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index c6cc77d2f366..602649919a9d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2941,8 +2941,12 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> else if ((gfp_mask & (__GFP_FS | __GFP_IO)) == 0)
> 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);
> + if (ret < 0)
> + schedule_timeout_uninterruptible(1);
> + } while ((gfp_mask & __GFP_NOFAIL) && (ret < 0));
>
1.
After that change a below code:
<snip>
if (ret < 0) {
warn_alloc(orig_gfp_mask, NULL,
"vmalloc error: size %lu, failed to map pages",
area->nr_pages * PAGE_SIZE);
goto fail;
}
<snip>
does not make any sense anymore.
2.
Can we combine two places where we handle __GFP_NOFAIL into one place?
That would look like as more sorted out.
--
Uladzislau Rezki
