On 09/15/25 at 03:40pm, Uladzislau Rezki (Sony) wrote:
> alloc_vmap_area() currently assumes that sleeping is allowed during
> allocation. This is not true for callers which pass non-blocking
> GFP flags, such as GFP_ATOMIC or GFP_NOWAIT.
>
> This patch adds logic to detect whether the given gfp_mask permits
> blocking. It avoids invoking might_sleep() or falling back to reclaim
> path if blocking is not allowed.
>
> This makes alloc_vmap_area() safer for use in non-sleeping contexts,
> where previously it could hit unexpected sleeps, trigger warnings.
>
> It is a preparation and adjustment step to later allow both GFP_ATOMIC
> and GFP_NOWAIT allocations in this series.
>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> ---
> mm/vmalloc.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
LGTM,
Reviewed-by: Baoquan He <bhe@redhat.com>
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5edd536ba9d2..49a0f81930a8 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2017,6 +2017,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> unsigned long freed;
> unsigned long addr;
> unsigned int vn_id;
> + bool allow_block;
> int purged = 0;
> int ret;
>
> @@ -2028,7 +2029,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>
> /* Only reclaim behaviour flags are relevant. */
> gfp_mask = gfp_mask & GFP_RECLAIM_MASK;
> - might_sleep();
> + allow_block = gfpflags_allow_blocking(gfp_mask);
> + might_sleep_if(allow_block);
>
> /*
> * If a VA is obtained from a global heap(if it fails here)
> @@ -2065,8 +2067,16 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> * If an allocation fails, the error value is
> * returned. Therefore trigger the overflow path.
> */
> - if (IS_ERR_VALUE(addr))
> - goto overflow;
> + if (IS_ERR_VALUE(addr)) {
> + if (allow_block)
> + goto overflow;
> +
> + /*
> + * We can not trigger any reclaim logic because
> + * sleeping is not allowed, thus fail an allocation.
> + */
> + goto out_free_va;
> + }
>
> va->va_start = addr;
> va->va_end = addr + size;
> @@ -2116,6 +2126,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> pr_warn("vmalloc_node_range for size %lu failed: Address range restricted to %#lx - %#lx\n",
> size, vstart, vend);
>
> +out_free_va:
> kmem_cache_free(vmap_area_cachep, va);
> return ERR_PTR(-EBUSY);
> }
> --
> 2.47.3
>