>
> it causes double align requirement for __get_vm_area_node() if parameter
> size is power of 2 and VM_IOREMAP is set in parameter flags
>
> it is fixed by handling the specail case manually due to lack of
> get_count_order() for long parameter
>
> ...
>
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1357,11 +1357,16 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
> {
> struct vmap_area *va;
> struct vm_struct *area;
> + int ioremap_size_order;
>
> BUG_ON(in_interrupt());
> - if (flags & VM_IOREMAP)
> - align = 1ul << clamp_t(int, fls_long(size),
> - PAGE_SHIFT, IOREMAP_MAX_ORDER);
> + if (flags & VM_IOREMAP) {
> + ioremap_size_order = fls_long(size);
> + if (is_power_of_2(size) && size != 1)
> + ioremap_size_order--;
> + align = 1ul << clamp_t(int, ioremap_size_order, PAGE_SHIFT,
> + IOREMAP_MAX_ORDER);
> + }
>
> size = PAGE_ALIGN(size);
> if (unlikely(!size))
I'm having trouble with this, and a more complete description would
have helped!
As far as I can tell, the current code will decide the following:
size=0x10000: alignment=0x10000
size=0x0f000: alignment=0x8000
And your patch will change it so that
size=0x10000: alignment=0x8000
size=0x0f000: alignment=0x8000
Correct?
If so, I'm struggling to see the sense in this. Shouldn't we be
changing things so that
size=0x10000: alignment=0x10000
size=0x0f000: alignment=0x10000
?
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