On Mon 17-03-14 20:49:28, Jan Kara wrote:
> Provide new function get_vaddr_pfns(). This function maps virtual
> addresses from given start and fills given array with page frame numbers of
> the corresponding pages. If given start belongs to a normal vma, the function
> grabs reference to each of the pages to pin them in memory. If start
> belongs to VM_IO | VM_PFNMAP vma, we don't touch page structures. Caller
> should make sure pfns aren't reused for anything else while he is using
> them.
>
> This function is created for various drivers to simplify handling of
> their buffers.
MM guys, could you have a look at this patch? Linux Media people like the
abstraction of buffer handling and would like to merge the patch set (see
http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/89268).
But for that they need ack from mm people that the interface is ok with
them. So far the only comment I got regarding the interface was from Dave
Hansen that I could also handle VM_MIXEDMAP mappings - I could if people
really want that but so far there are no users for that. Thanks!
Honza
>
> Signed-off-by: Jan Kara <j...@suse.cz>
> ---
> include/linux/mm.h | 46 +++++++++++++++
> mm/memory.c | 165
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 211 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index da8ad480bea7..b3bd29cc40dd 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -18,6 +18,8 @@
> #include <linux/pfn.h>
> #include <linux/bit_spinlock.h>
> #include <linux/shrinker.h>
> +#include <linux/slab.h>
> +#include <linux/vmalloc.h>
>
> struct mempolicy;
> struct anon_vma;
> @@ -1180,6 +1182,50 @@ get_user_pages_unlocked(struct task_struct *tsk,
> struct mm_struct *mm,
> return ret;
> }
>
> +/* Container for pinned pfns / pages */
> +struct pinned_pfns {
> + unsigned int nr_allocated_pfns; /* Number of pfns we have space for */
> + unsigned int nr_pfns; /* Number of pfns stored in pfns array
> */
> + unsigned int got_ref:1; /* Did we pin pfns by getting page ref?
> */
> + unsigned int is_pages:1; /* Does array contain pages or pfns? */
> + void *ptrs[0]; /* Array of pinned pfns / pages.
> + * Use pfns_vector_pages() or
> + * pfns_vector_pfns() for access */
> +};
> +
> +struct pinned_pfns *pfns_vector_create(int nr_pfns);
> +static inline void pfns_vector_destroy(struct pinned_pfns *pfns)
> +{
> + if (!is_vmalloc_addr(pfns))
> + kfree(pfns);
> + else
> + vfree(pfns);
> +}
> +int get_vaddr_pfns(unsigned long start, int nr_pfns, int write, int force,
> + struct pinned_pfns *pfns);
> +void put_vaddr_pfns(struct pinned_pfns *pfns);
> +int pfns_vector_to_pages(struct pinned_pfns *pfns);
> +
> +static inline int pfns_vector_count(struct pinned_pfns *pfns)
> +{
> + return pfns->nr_pfns;
> +}
> +
> +static inline struct page **pfns_vector_pages(struct pinned_pfns *pfns)
> +{
> + if (!pfns->is_pages)
> + return NULL;
> + return (struct page **)(pfns->ptrs);
> +}
> +
> +static inline unsigned long *pfns_vector_pfns(struct pinned_pfns *pfns)
> +{
> + if (pfns->is_pages)
> + return NULL;
> + return (unsigned long *)(pfns->ptrs);
> +}
> +
> +
> struct kvec;
> int get_kernel_pages(const struct kvec *iov, int nr_pages, int write,
> struct page **pages);
> diff --git a/mm/memory.c b/mm/memory.c
> index 22dfa617bddb..87bebcfb8911 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2024,6 +2024,171 @@ long get_user_pages(struct task_struct *tsk, struct
> mm_struct *mm,
> EXPORT_SYMBOL(get_user_pages);
>
> /**
> + * get_vaddr_pfns() - map virtual addresses to pfns
> + * @start: starting user address
> + * @nr_pfns: number of pfns from start to map
> + * @write: whether pages will be written to by the caller
> + * @force: whether to force write access even if user mapping is
> + * readonly. This will result in the page being COWed even
> + * in MAP_SHARED mappings. You do not want this.
> + * @pfns: structure which receives pfns of the pages mapped.
> + * It should have space for at least nr_pfns pfns.
> + *
> + * This function maps virtual addresses from @start and fills @pfns structure
> + * with page frame numbers of corresponding pages. If @start belongs to a
> + * normal vma, the function grabs reference to each of the pages to pin them
> in
> + * memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't touch page
> + * structures. Caller should make sure pfns aren't reused for anything else
> + * while he is using them.
> + *
> + * This function takes care of grabbing mmap_sem as necessary.
> + */
> +int get_vaddr_pfns(unsigned long start, int nr_pfns, int write, int force,
> + struct pinned_pfns *pfns)
> +{
> + struct mm_struct *mm = current->mm;
> + struct vm_area_struct *vma;
> + int ret = 0;
> + int err;
> +
> + if (nr_pfns <= 0)
> + return 0;
> +
> + if (nr_pfns > pfns->nr_allocated_pfns)
> + nr_pfns = pfns->nr_allocated_pfns;
> +
> + down_read(&mm->mmap_sem);
> + vma = find_vma_intersection(mm, start, start + 1);
> + if (!vma) {
> + ret = -EFAULT;
> + goto out;
> + }
> + if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
> + pfns->got_ref = 1;
> + pfns->is_pages = 1;
> + ret = get_user_pages(current, mm, start, nr_pfns, write, force,
> + pfns_vector_pages(pfns), NULL);
> + goto out;
> + }
> +
> + pfns->got_ref = 0;
> + pfns->is_pages = 0;
> + do {
> + unsigned long *nums = pfns_vector_pfns(pfns);
> +
> + while (ret < nr_pfns && start + PAGE_SIZE <= vma->vm_end) {
> + err = follow_pfn(vma, start, &nums[ret]);
> + if (err) {
> + if (ret == 0)
> + ret = err;
> + goto out;
> + }
> + start += PAGE_SIZE;
> + ret++;
> + }
> + /*
> + * We stop if we have enough pages or if VMA doesn't completely
> + * cover the tail page.
> + */
> + if (ret >= nr_pfns || start < vma->vm_end)
> + break;
> + vma = find_vma_intersection(mm, start, start + 1);
> + } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
> +out:
> + up_read(&mm->mmap_sem);
> + if (!ret)
> + ret = -EFAULT;
> + if (ret > 0)
> + pfns->nr_pfns = ret;
> + return ret;
> +}
> +EXPORT_SYMBOL(get_vaddr_pfns);
> +
> +/**
> + * put_vaddr_pfns() - drop references to pages if get_vaddr_pfns() acquired
> them
> + * @pfns: structure with pfns we pinned
> + *
> + * Drop references to pages if get_vaddr_pfns() acquired them. We also
> + * invalidate the array of pfns so that it is prepared for the next call into
> + * get_vaddr_pfns().
> + */
> +void put_vaddr_pfns(struct pinned_pfns *pfns)
> +{
> + int i;
> +
> + if (!pfns->got_ref)
> + goto out;
> + if (pfns->is_pages) {
> + struct page **pages = pfns_vector_pages(pfns);
> +
> + for (i = 0; i < pfns->nr_pfns; i++)
> + put_page(pages[i]);
> + } else {
> + unsigned long *nums = pfns_vector_pfns(pfns);
> +
> + for (i = 0; i < pfns->nr_pfns; i++)
> + put_page(pfn_to_page(nums[i]));
> + }
> + pfns->got_ref = 0;
> +out:
> + pfns->nr_pfns = 0;
> +}
> +EXPORT_SYMBOL(put_vaddr_pfns);
> +
> +/**
> + * pfns_vector_to_pages - convert vector of pfns to vector of page pointers
> + * @pfns: structure with pinned pfns
> + *
> + * Convert @pfns to not contain array of pfns but array of page pointers.
> + * If the conversion is successful, return 0. Otherwise return an error.
> + */
> +int pfns_vector_to_pages(struct pinned_pfns *pfns)
> +{
> + int i;
> + unsigned long *nums;
> + struct page **pages;
> +
> + if (pfns->is_pages)
> + return 0;
> + nums = pfns_vector_pfns(pfns);
> + for (i = 0; i < pfns->nr_pfns; i++)
> + if (!pfn_valid(nums[i]))
> + return -EINVAL;
> + pages = (struct page **)nums;
> + for (i = 0; i < pfns->nr_pfns; i++)
> + pages[i] = pfn_to_page(nums[i]);
> + pfns->is_pages = 1;
> + return 0;
> +}
> +EXPORT_SYMBOL(pfns_vector_to_pages);
> +
> +/**
> + * pfns_vector_create() - allocate & initialize structure for pinned pfns
> + * @nr_pfns: number of pfns slots we should reserve
> + *
> + * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
> + * pfns.
> + */
> +struct pinned_pfns *pfns_vector_create(int nr_pfns)
> +{
> + struct pinned_pfns *pfns;
> + int size = sizeof(struct pinned_pfns) + sizeof(unsigned long) * nr_pfns;
> +
> + if (WARN_ON_ONCE(nr_pfns <= 0))
> + return NULL;
> + if (size <= PAGE_SIZE)
> + pfns = kmalloc(size, GFP_KERNEL);
> + else
> + pfns = vmalloc(size);
> + if (!pfns)
> + return NULL;
> + pfns->nr_allocated_pfns = nr_pfns;
> + pfns->nr_pfns = 0;
> + return 0;
> +}
> +EXPORT_SYMBOL(pfns_vector_create);
> +
> +/**
> * get_dump_page() - pin user page in memory while writing it to core dump
> * @addr: user address
> *
> --
> 1.8.1.4
>
--
Jan Kara <j...@suse.cz>
SUSE Labs, CR
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