Re: [PATCH v5 3/3] ARM: mm: use static_vm for managing static mappedareas

[Joonsoo Kim]

Hello, Nicolas.

On Mon, Feb 04, 2013 at 11:44:16PM -0500, Nicolas Pitre wrote:
> On Tue, 5 Feb 2013, Joonsoo Kim wrote:
> 
> > A static mapped area is ARM-specific, so it is better not to use
> > generic vmalloc data structure, that is, vmlist and vmlist_lock
> > for managing static mapped area. And it causes some needless overhead and
> > reducing this overhead is better idea.
> > 
> > Now, we have newly introduced static_vm infrastructure.
> > With it, we don't need to iterate all mapped areas. Instead, we just
> > iterate static mapped areas. It helps to reduce an overhead of finding
> > matched area. And architecture dependency on vmalloc layer is removed,
> > so it will help to maintainability for vmalloc layer.
> > 
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> 
> Some comments below.
> 
> > diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
> > index 904c15e..c7fef4b 100644
> > --- a/arch/arm/mm/ioremap.c
> > +++ b/arch/arm/mm/ioremap.c
> > @@ -261,13 +261,14 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
> >  	const struct mem_type *type;
> >  	int err;
> >  	unsigned long addr;
> > - 	struct vm_struct * area;
> > +	struct vm_struct *area;
> > +	phys_addr_t paddr = __pfn_to_phys(pfn);
> >  
> >  #ifndef CONFIG_ARM_LPAE
> >  	/*
> >  	 * High mappings must be supersection aligned
> >  	 */
> > -	if (pfn >= 0x100000 && (__pfn_to_phys(pfn) & ~SUPERSECTION_MASK))
> > +	if (pfn >= 0x100000 && (paddr & ~SUPERSECTION_MASK))
> >  		return NULL;
> >  #endif
> >  
> > @@ -283,24 +284,16 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
> >  	/*
> >  	 * Try to reuse one of the static mapping whenever possible.
> >  	 */
> > -	read_lock(&vmlist_lock);
> > -	for (area = vmlist; area; area = area->next) {
> > -		if (!size || (sizeof(phys_addr_t) == 4 && pfn >= 0x100000))
> > -			break;
> > -		if (!(area->flags & VM_ARM_STATIC_MAPPING))
> > -			continue;
> > -		if ((area->flags & VM_ARM_MTYPE_MASK) != VM_ARM_MTYPE(mtype))
> > -			continue;
> > -		if (__phys_to_pfn(area->phys_addr) > pfn ||
> > -		    __pfn_to_phys(pfn) + size-1 > area->phys_addr + area->size-1)
> > -			continue;
> > -		/* we can drop the lock here as we know *area is static */
> > -		read_unlock(&vmlist_lock);
> > -		addr = (unsigned long)area->addr;
> > -		addr += __pfn_to_phys(pfn) - area->phys_addr;
> > -		return (void __iomem *) (offset + addr);
> > +	if (size && !((sizeof(phys_addr_t) == 4 && pfn >= 0x100000))) {
>                      ^                                             ^
> You have a needless extra set of parents here.
 
Okay.

> [...]
> 
> > diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> > index ce328c7..b2c0356 100644
> > --- a/arch/arm/mm/mmu.c
> > +++ b/arch/arm/mm/mmu.c
> > @@ -757,21 +757,24 @@ void __init iotable_init(struct map_desc *io_desc, int nr)
> >  {
> >  	struct map_desc *md;
> >  	struct vm_struct *vm;
> > +	struct static_vm *svm;
> >  
> >  	if (!nr)
> >  		return;
> >  
> > -	vm = early_alloc_aligned(sizeof(*vm) * nr, __alignof__(*vm));
> > +	svm = early_alloc_aligned(sizeof(*svm) * nr, __alignof__(*svm));
> >  
> >  	for (md = io_desc; nr; md++, nr--) {
> >  		create_mapping(md);
> > +
> > +		vm = &svm->vm;
> >  		vm->addr = (void *)(md->virtual & PAGE_MASK);
> >  		vm->size = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK));
> >  		vm->phys_addr = __pfn_to_phys(md->pfn);
> >  		vm->flags = VM_IOREMAP | VM_ARM_STATIC_MAPPING;
> >  		vm->flags |= VM_ARM_MTYPE(md->type);
> >  		vm->caller = iotable_init;
> > -		vm_area_add_early(vm++);
> > +		add_static_vm_early(svm++);
> >  	}
> >  }
> >  
> > @@ -779,13 +782,16 @@ void __init vm_reserve_area_early(unsigned long addr, unsigned long size,
> >  				  void *caller)
> >  {
> >  	struct vm_struct *vm;
> > +	struct static_vm *svm;
> > +
> > +	svm = early_alloc_aligned(sizeof(*svm), __alignof__(*svm));
> >  
> > -	vm = early_alloc_aligned(sizeof(*vm), __alignof__(*vm));
> > +	vm = &svm->vm;
> >  	vm->addr = (void *)addr;
> >  	vm->size = size;
> >  	vm->flags = VM_IOREMAP | VM_ARM_EMPTY_MAPPING;
> >  	vm->caller = caller;
> > -	vm_area_add_early(vm);
> > +	add_static_vm_early(svm);
> >  }
> >  
> >  #ifndef CONFIG_ARM_LPAE
> > @@ -810,14 +816,13 @@ static void __init pmd_empty_section_gap(unsigned long addr)
> >  
> >  static void __init fill_pmd_gaps(void)
> >  {
> > +	struct static_vm *svm;
> >  	struct vm_struct *vm;
> >  	unsigned long addr, next = 0;
> >  	pmd_t *pmd;
> >  
> > -	/* we're still single threaded hence no lock needed here */
> > -	for (vm = vmlist; vm; vm = vm->next) {
> > -		if (!(vm->flags & (VM_ARM_STATIC_MAPPING | VM_ARM_EMPTY_MAPPING)))
> > -			continue;
> > +	list_for_each_entry(svm, &static_vmlist, list) {
> > +		vm = &svm->vm;
> >  		addr = (unsigned long)vm->addr;
> >  		if (addr < next)
> >  			continue;
> > @@ -859,17 +864,12 @@ static void __init pci_reserve_io(void)
> >  {
> >  	struct vm_struct *vm;
> >  	unsigned long addr;
> > +	struct static_vm *svm;
> >  
> > -	/* we're still single threaded hence no lock needed here */
> > -	for (vm = vmlist; vm; vm = vm->next) {
> > -		if (!(vm->flags & VM_ARM_STATIC_MAPPING))
> > -			continue;
> > -		addr = (unsigned long)vm->addr;
> > -		addr &= ~(SZ_2M - 1);
> > -		if (addr == PCI_IO_VIRT_BASE)
> > -			return;
> > +	svm = find_static_vm_vaddr((void *)PCI_IO_VIRT_BASE);
> > +	if (svm)
> > +		return;
> > 
> > -	}
> >  
> >  	vm_reserve_area_early(PCI_IO_VIRT_BASE, SZ_2M, pci_reserve_io);
> >  }
> 
> The replacement code is not equivalent.  I can't recall why the original 
> is as it is, but it doesn't look right to me.  The 2MB round down 
> certainly looks suspicious.
> 
> The replacement code should be better.  However I'd like you to get an 
> ACK from Rob Herring as well for this patch.
> 
> Once that is sorted out, you can add
> 
> Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>

Okay. I will fix this and re-send it with your "Reviewed-by".

Thanks.

> 
> Nicolas
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