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Message-ID: <ZerLB/LNWAOvC2HM@MiWiFi-R3L-srv>
Date: Fri, 8 Mar 2024 16:23:35 +0800
From: Baoquan He <bhe@...hat.com>
To: Uladzislau Rezki <urezki@...il.com>
Cc: rulinhuang <rulin.huang@...el.com>, akpm@...ux-foundation.org,
colin.king@...el.com, hch@...radead.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
lstoakes@...il.com, tianyou.li@...el.com, tim.c.chen@...el.com,
wangyang.guo@...el.com, zhiguo.zhou@...el.com
Subject: Re: [PATCH v7 1/2] mm/vmalloc: Moved macros with no functional
change happened
On 03/07/24 at 08:16pm, Uladzislau Rezki wrote:
> On Thu, Mar 07, 2024 at 09:23:10AM +0800, Baoquan He wrote:
> > On 03/06/24 at 08:01pm, Uladzislau Rezki wrote:
> > > On Fri, Mar 01, 2024 at 10:54:16AM -0500, rulinhuang wrote:
> > ......
> > >
> > > Sorry for the late answer, i also just noticed this email. It was not in
> > > my inbox...
> > >
> > > OK, now you move part of the per-cpu allocator on the top and leave
> > > another part down making it split. This is just for the:
> > >
> > > BUG_ON(va_flags & VMAP_RAM);
> > >
> > > VMAP_RAM macro. Do we really need this BUG_ON()?
> >
> > Sorry, I suggested that when reviewing v5:
> > https://lore.kernel.org/all/ZdiltpK5fUvwVWtD@MiWiFi-R3L-srv/T/#u
> >
> > About part of per-cpu kva allocator moving and the split making, I would
> > argue that we will have vmap_nodes defintion and basic helper functions
> > like addr_to_node_id() etc at top, and leave other part like
> > size_to_va_pool(), node_pool_add_va() etc down. These are similar.
> >
> > While about whether we should add 'BUG_ON(va_flags & VMAP_RAM);', I am
> > not sure about it. When I suggested that, I am also hesitant. From the
> > current code, alloc_vmap_area() is called in below three functions, only
> > __get_vm_area_node() will pass the non-NULL vm.
> > new_vmap_block() -|
> > vm_map_ram() ----> alloc_vmap_area()
> > __get_vm_area_node() -|
> >
> > It could be wrongly passed in the future? Only checking if vm is
> > non-NULL makes me feel a little unsafe. While I am fine if removing the
> > BUG_ON, because there's no worry in the current code. We can wait and
> > see in the future.
> >
> > if (vm) {
> > BUG_ON(va_flags & VMAP_RAM);
> > setup_vmalloc_vm(vm, va, flags, caller);
> > }
> >
> I would remove it, because it is really hard to mess it, there is only
> one place also BUG_ON() is really a show stopper. I really appreciate
> what rulinhuang <rulin.huang@...el.com> is doing and i understand that
> it might be not so easy.
I agree, I was hesitant, now it firms up my mind.
>
> So, if we can avoid of moving the code, that looks to me that we can do,
> if we can pass less arguments into alloc_vmap_area() since it is overloaded
> that would be great.
Agree too, less arguments is much better. While I personnally prefer the open
coding a little bit like below. There is suspicion of excessive packaging in
__pre/__post_setup_vmalloc_vm() wrapping. They are very simple and few
assignments after all.
---
mm/vmalloc.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 0fd8ebaad17b..0c738423976d 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1924,8 +1924,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
unsigned long align,
unsigned long vstart, unsigned long vend,
int node, gfp_t gfp_mask,
- unsigned long va_flags, struct vm_struct *vm,
- unsigned long flags, const void *caller)
+ unsigned long va_flags, struct vm_struct *vm)
{
struct vmap_node *vn;
struct vmap_area *va;
@@ -1988,8 +1987,11 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
va->vm = NULL;
va->flags = (va_flags | vn_id);
- if (vm)
- setup_vmalloc_vm(vm, va, flags, caller);
+ if (vm) {
+ vm->addr = (void *)va->va_start;
+ vm->size = va->va_end - va->va_start;
+ va->vm = vm;
+ }
vn = addr_to_node(va->va_start);
@@ -2565,8 +2567,7 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE,
VMALLOC_START, VMALLOC_END,
node, gfp_mask,
- VMAP_RAM|VMAP_BLOCK, NULL,
- 0, NULL);
+ VMAP_RAM|VMAP_BLOCK, NULL);
if (IS_ERR(va)) {
kfree(vb);
return ERR_CAST(va);
@@ -2924,7 +2925,7 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
va = alloc_vmap_area(size, PAGE_SIZE,
VMALLOC_START, VMALLOC_END,
node, GFP_KERNEL, VMAP_RAM,
- NULL, 0, NULL);
+ NULL);
if (IS_ERR(va))
return NULL;
@@ -3063,7 +3064,10 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
if (!(flags & VM_NO_GUARD))
size += PAGE_SIZE;
- va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0, area, flags, caller);
+ area->flags = flags;
+ area->caller = caller;
+
+ va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0, area);
if (IS_ERR(va)) {
kfree(area);
return NULL;
--
2.41.0
>
> Just an example:
>
> <snip>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 25a8df497255..b6050e018539 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1841,6 +1841,30 @@ node_alloc(unsigned long size, unsigned long align,
> return va;
> }
>
> +static inline void
> +__pre_setup_vmalloc_vm(struct vm_struct *vm,
> + unsigned long flags, const void *caller)
> +{
> + vm->flags = flags;
> + vm->caller = caller;
> +}
> +
> +static inline void
> +__post_setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va)
> +{
> + vm->addr = (void *)va->va_start;
> + vm->size = va->va_end - va->va_start;
> + va->vm = vm;
> +}
> +
> +static inline void
> +setup_vmalloc_vm_locked(struct vm_struct *vm, struct vmap_area *va,
> + unsigned long flags, const void *caller)
> +{
> + __pre_setup_vmalloc_vm(vm, flags, caller);
> + __post_setup_vmalloc_vm(vm, va);
> +}
> +
> /*
> * Allocate a region of KVA of the specified size and alignment, within the
> * vstart and vend.
> @@ -1849,7 +1873,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> unsigned long align,
> unsigned long vstart, unsigned long vend,
> int node, gfp_t gfp_mask,
> - unsigned long va_flags)
> + unsigned long va_flags, struct vm_struct *vm)
> {
> struct vmap_node *vn;
> struct vmap_area *va;
> @@ -1912,6 +1936,9 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> va->vm = NULL;
> va->flags = (va_flags | vn_id);
>
> + if (vm)
> + __post_setup_vmalloc_vm(vm, va);
> +
> vn = addr_to_node(va->va_start);
>
> spin_lock(&vn->busy.lock);
> @@ -2486,7 +2513,7 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
> va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE,
> VMALLOC_START, VMALLOC_END,
> node, gfp_mask,
> - VMAP_RAM|VMAP_BLOCK);
> + VMAP_RAM|VMAP_BLOCK, NULL);
> if (IS_ERR(va)) {
> kfree(vb);
> return ERR_CAST(va);
> @@ -2843,7 +2870,8 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
> struct vmap_area *va;
> va = alloc_vmap_area(size, PAGE_SIZE,
> VMALLOC_START, VMALLOC_END,
> - node, GFP_KERNEL, VMAP_RAM);
> + node, GFP_KERNEL, VMAP_RAM, NULL);
> +
> if (IS_ERR(va))
> return NULL;
>
> @@ -2946,26 +2974,6 @@ void __init vm_area_register_early(struct vm_struct *vm, size_t align)
> kasan_populate_early_vm_area_shadow(vm->addr, vm->size);
> }
>
> -static inline void setup_vmalloc_vm_locked(struct vm_struct *vm,
> - struct vmap_area *va, unsigned long flags, const void *caller)
> -{
> - vm->flags = flags;
> - vm->addr = (void *)va->va_start;
> - vm->size = va->va_end - va->va_start;
> - vm->caller = caller;
> - va->vm = vm;
> -}
> -
> -static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
> - unsigned long flags, const void *caller)
> -{
> - struct vmap_node *vn = addr_to_node(va->va_start);
> -
> - spin_lock(&vn->busy.lock);
> - setup_vmalloc_vm_locked(vm, va, flags, caller);
> - spin_unlock(&vn->busy.lock);
> -}
> -
> static void clear_vm_uninitialized_flag(struct vm_struct *vm)
> {
> /*
> @@ -3002,14 +3010,15 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
> if (!(flags & VM_NO_GUARD))
> size += PAGE_SIZE;
>
> - va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0);
> + /* post-setup is done in the alloc_vmap_area(). */
> + __pre_setup_vmalloc_vm(area, flags, caller);
> +
> + va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0, area);
> if (IS_ERR(va)) {
> kfree(area);
> return NULL;
> }
>
> - setup_vmalloc_vm(area, va, flags, caller);
> -
> /*
> * Mark pages for non-VM_ALLOC mappings as accessible. Do it now as a
> * best-effort approach, as they can be mapped outside of vmalloc code.
> <snip>
>
> --
> Uladzislau Rezki
>
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