On Mon, Aug 02, 2021 at 10:39:04AM +0800, Kefeng Wang wrote:
> On 2021/8/1 23:23, Catalin Marinas wrote:
> > On Tue, Jul 20, 2021 at 10:51:03AM +0800, Kefeng Wang wrote:
> > > There are some fixed locations in the vmalloc area be reserved
> > > in ARM(see iotable_init()) and ARM64(see map_kernel()), but for
> > > pcpu_page_first_chunk(), it calls vm_area_register_early() and
> > > choose VMALLOC_START as the start address of vmap area which
> > > could be conflicted with above address, then could trigger a
> > > BUG_ON in vm_area_add_early().
> > >
> > > Let's choose the end of existing address range in vmlist as the
> > > start address instead of VMALLOC_START to avoid the BUG_ON.
> > >
> > > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > > ---
> > > mm/vmalloc.c | 8 +++++---
> > > 1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > > index d5cd52805149..a98cf97f032f 100644
> > > --- a/mm/vmalloc.c
> > > +++ b/mm/vmalloc.c
> > > @@ -2238,12 +2238,14 @@ void __init vm_area_add_early(struct vm_struct *vm)
> > > */
> > > void __init vm_area_register_early(struct vm_struct *vm, size_t align)
> > > {
> > > - static size_t vm_init_off __initdata;
> > > + unsigned long vm_start = VMALLOC_START;
> > > + struct vm_struct *tmp;
> > > unsigned long addr;
> > > - addr = ALIGN(VMALLOC_START + vm_init_off, align);
> > > - vm_init_off = PFN_ALIGN(addr + vm->size) - VMALLOC_START;
> > > + for (tmp = vmlist; tmp; tmp = tmp->next)
> > > + vm_start = (unsigned long)tmp->addr + tmp->size;
> > > + addr = ALIGN(vm_start, align);
> > > vm->addr = (void *)addr;
> > > vm_area_add_early(vm);
> > Is there a risk of breaking other architectures? It doesn't look like to
> > me but I thought I'd ask.
>
> Before this patch, vm_init_off is to record the offset from VMALLOC_START,
>
> but it use VMALLOC_START as start address on the function
> vm_area_register_early()
>
> called firstly, this will cause the BUG_ON.
>
> With this patch, the most important change is that we choose the start
> address via
>
> dynamic calculate the 'start' address by traversing the list.
>
> [wkf@localhost linux-next]$ git grep vm_area_register_early
> arch/alpha/mm/init.c: vm_area_register_early(&console_remap_vm, PAGE_SIZE);
> arch/x86/xen/p2m.c: vm_area_register_early(&vm, PMD_SIZE *
> PMDS_PER_MID_PAGE);
> mm/percpu.c: vm_area_register_early(&vm, PAGE_SIZE);
> [wkf@localhost linux-next]$ git grep vm_area_add_early
> arch/arm/mm/ioremap.c: vm_area_add_early(vm);
> arch/arm64/mm/mmu.c: vm_area_add_early(vma);
>
> x86/alpha won't call vm_area_add_early(), only arm64 could call both vm_area_add_early()
> and vm_area_register_early() when this patchset is merged. so it won't break other architectures.
Thanks for checking.
> > Also, instead of always picking the end, could we search for a range
> > that fits?
>
> We only need a space in vmalloc range, using end or a range in the middle
> is not different.
I was thinking of making it more future-proof in case one registers a
vm area towards the end of the range. It's fairly easy to pick a range
in the middle now that you are adding a list traversal.
--
Catalin
