Re: [RFC][PATCH 1/2] mm/vmalloc: Add IO mapping space reused interface.

Rob Herring
2014-05-13T03:13:29Z

On Sun, May 11, 2014 at 9:19 PM, Richard Lee <superlibj8301@gmail.com> wrote:
> For the IO mapping, for the same physical address space maybe
> mapped more than one time, for example, in some SoCs:
> 0x20000000 ~ 0x20001000: are global control IO physical map,
> and this range space will be used by many drivers.

What address or who the user is isn't really relevant.

> And then if each driver will do the same ioremap operation, we
> will waste to much malloc virtual spaces.

s/malloc/vmalloc/

>
> This patch add the IO mapping space reusing interface:
> - find_vm_area_paddr: used to find the exsit vmalloc area using

s/exsit/exist/

> the IO physical address.
> - vm_area_is_aready_to_free: before vfree the IO mapped areas
> using this to do the check that if this area is used by more
> than one consumer.
>
> Signed-off-by: Richard Lee <superlibj@gmail.com>
> ---
> include/linux/vmalloc.h | 5 ++++
> mm/vmalloc.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 68 insertions(+)
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 4b8a891..2b811f6 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -34,6 +34,7 @@ struct vm_struct {
> struct page **pages;
> unsigned int nr_pages;
> phys_addr_t phys_addr;
> + unsigned int used;
> const void *caller;
> };
>
> @@ -100,6 +101,10 @@ static inline size_t get_vm_area_size(const struct vm_struct *area)
> return area->size - PAGE_SIZE;
> }
>
> +extern int vm_area_is_aready_to_free(phys_addr_t addr);
> +struct vm_struct *find_vm_area_paddr(phys_addr_t paddr, size_t size,
> + unsigned long *offset,
> + unsigned long flags);
> extern struct vm_struct *get_vm_area(unsigned long size, unsigned long flags);
> extern struct vm_struct *get_vm_area_caller(unsigned long size,
> unsigned long flags, const void *caller);
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index bf233b2..f75b7b3 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1293,6 +1293,7 @@ static void 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;
> vm->caller = caller;
> + vm->used = 1;
> va->vm = vm;
> va->flags |= VM_VM_AREA;
> spin_unlock(&vmap_area_lock);
> @@ -1383,6 +1384,68 @@ struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
> NUMA_NO_NODE, GFP_KERNEL, caller);
> }
>
> +int vm_area_is_aready_to_free(phys_addr_t addr)

aready is not a word.

> +{
> + struct vmap_area *va;
> +
> + va = find_vmap_area((unsigned long)addr);
> + if (!va || !(va->flags & VM_VM_AREA) || !va->vm)
> + return 1;
> +
> + if (va->vm->used <= 1)
> + return 1;
> +
> + --va->vm->used;

What lock protects this? You should use atomic ops here.

> +
> + return 0;
> +}
> +
> +/**
> + * find_vm_area_paddr - find a continuous kernel virtual area using the
> + * physical addreess.
> + * @paddr: base physical address
> + * @size: size of the physical area range
> + * @offset: the start offset of the vm area
> + * @flags: %VM_IOREMAP for I/O mappings
> + *
> + * Search for the kernel VM area, whoes physical address starting at @paddr,
> + * and if the exsit VM area's size is large enough, then just return it, or
> + * return NULL.
> + */
> +struct vm_struct *find_vm_area_paddr(phys_addr_t paddr, size_t size,
> + unsigned long *offset,
> + unsigned long flags)
> +{
> + struct vmap_area *va;
> +
> + if (!(flags & VM_IOREMAP))
> + return NULL;
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(va, &vmap_area_list, list) {
> + phys_addr_t phys_addr;
> +
> + if (!va || !(va->flags & VM_VM_AREA) || !va->vm)
> + continue;
> +
> + phys_addr = va->vm->phys_addr;
> +
> + if (paddr < phys_addr || paddr + size > phys_addr + va->vm->size)
> + continue;
> +
> + *offset = paddr - phys_addr;
> +
> + if (va->vm->flags & VM_IOREMAP && va->vm->size >= size) {
> + va->vm->used++;

What lock protects this? It looks like you are modifying this with
only a rcu reader lock.

> + rcu_read_unlock();
> + return va->vm;
> + }
> + }
> + rcu_read_unlock();
> +
> + return NULL;
> +}
> +
> /**
> * find_vm_area - find a continuous kernel virtual area
> * @addr: base address
> --
> 1.8.4
>
>
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