Re: [PATCH v9 11/12] mm/vmalloc: Hugepage vmalloc mappings

From: Ding Tianhong
Date: Fri Dec 25 2020 - 02:59:35 EST



> +again:
> + size = PAGE_ALIGN(size);
> + area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
> vm_flags, start, end, node, gfp_mask, caller);
> if (!area)
> goto fail;
>
> - addr = __vmalloc_area_node(area, gfp_mask, prot, node);
> + addr = __vmalloc_area_node(area, gfp_mask, prot, shift, node);
> if (!addr)
> - return NULL;
> + goto fail;
>
> /*
> * In this function, newly allocated vm_struct has VM_UNINITIALIZED
> @@ -2788,8 +2878,19 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
> return addr;
>
> fail:
> - warn_alloc(gfp_mask, NULL,
> + if (shift > PAGE_SHIFT) {
> + free_vm_area(area);
> + shift = PAGE_SHIFT;
> + align = real_align;
> + size = real_size;
> + goto again;
> + }
> +
Hi, Nicholas:

I met a problem like this:

[ 67.103584] ------------[ cut here ]------------
[ 67.103884] kernel BUG at vmalloc.c:2892!
[ 67.104387] Internal error: Oops - BUG: 0 [#1] SMP
[ 67.104942] Process insmod (pid: 1161, stack limit = 0x(____ptrval____))
[ 67.105356] CPU: 2 PID: 1161 Comm: insmod Tainted: G O 4.19.95+ #9
[ 67.105702] Hardware name: linux,dummy-virt (DT)
[ 67.106006] pstate: a0000005 (NzCv daif -PAN -UAO)
[ 67.106285] pc : free_vm_area+0x78/0x80
[ 67.106549] lr : free_vm_area+0x58/0x80

it looks like when __vmalloc_area_node failed, the area is already released, and the free_vm_area
will release the vm area again, so trigger the problem.

3405 ret = remove_vm_area(area->addr);
3406 BUG_ON(ret != area);
3407 kfree(area);


Ding
> + if (!area) {
> + /* Warn for area allocation, page allocations already warn */
> + warn_alloc(gfp_mask, NULL,
> "vmalloc: allocation failure: %lu bytes", real_size);
> + }
> return NULL;
> }
>
>