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 <jack@xxxxxxx> > --- > 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 <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
