/** * get_user_pages_fast() - pin user pages in memory * @start: starting user address * @nr_pages: number of pages from start to pin * @write: whether pages will be written to * @pages: array that receives pointers to the pages pinned. * Should be at least nr_pages long. * * Attempt to pin user pages in memory without taking mm->mmap_sem. * If not successful, it will fall back to taking the lock and * calling get_user_pages(). * * Returns number of pages pinned. This may be fewer than the number * requested. If nr_pages is 0 or negative, returns 0. If no pages * were pinned, returns -errno. */ int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { struct mm_struct *mm = current->mm; unsigned long addr, len, end; unsigned long next; pgd_t *pgdp; int nr = 0; start &= PAGE_MASK; addr = start; len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; if (end < start) goto slow_irqon; local_irq_disable(); pgdp = pgd_offset(mm, addr); do { pgd_t pgd = *pgdp; next = pgd_addr_end(addr, end); if (pgd_none(pgd)) goto slow; if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) goto slow; } while (pgdp++, addr = next, addr != end); local_irq_enable(); VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); return nr; { int ret; slow: local_irq_enable(); slow_irqon: /* Try to get the remaining pages with get_user_pages */ start += nr << PAGE_SHIFT; pages += nr; down_read(&mm->mmap_sem); ret = get_user_pages(current, mm, start, (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); up_read(&mm->mmap_sem); /* Have to be a bit careful with return values */ if (nr > 0) { if (ret < 0) ret = nr; else ret += nr; } return ret; } }
/* * Like get_user_pages_fast() except its IRQ-safe in that it won't fall * back to the regular GUP. */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { struct mm_struct *mm = current->mm; unsigned long addr, len, end; unsigned long next; unsigned long flags; pgd_t *pgdp; int nr = 0; start &= PAGE_MASK; addr = start; len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, (void __user *)start, len))) return 0; /* * This doesn't prevent pagetable teardown, but does prevent * the pagetables and pages from being freed. */ local_irq_save(flags); pgdp = pgd_offset(mm, addr); do { pgd_t pgd = *pgdp; next = pgd_addr_end(addr, end); if (pgd_none(pgd)) break; if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) break; } while (pgdp++, addr = next, addr != end); local_irq_restore(flags); return nr; }
int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { struct mm_struct *mm = current->mm; unsigned long addr, len, end; unsigned long next; unsigned long flags; pgd_t *pgdp; int nr = 0; pr_devel("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read"); start &= PAGE_MASK; addr = start; len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, start, len))) return 0; pr_devel(" aligned: %lx .. %lx\n", start, end); /* * XXX: batch / limit 'nr', to avoid large irq off latency * needs some instrumenting to determine the common sizes used by * important workloads (eg. DB2), and whether limiting the batch size * will decrease performance. * * It seems like we're in the clear for the moment. Direct-IO is * the main guy that batches up lots of get_user_pages, and even * they are limited to 64-at-a-time which is not so many. */ /* * This doesn't prevent pagetable teardown, but does prevent * the pagetables from being freed on powerpc. * * So long as we atomically load page table pointers versus teardown, * we can follow the address down to the the page and take a ref on it. */ local_irq_save(flags); pgdp = pgd_offset(mm, addr); do { pgd_t pgd = READ_ONCE(*pgdp); pr_devel(" %016lx: normal pgd %p\n", addr, (void *)pgd_val(pgd)); next = pgd_addr_end(addr, end); if (pgd_none(pgd)) break; if (pgd_huge(pgd)) { if (!gup_hugepte((pte_t *)pgdp, PGDIR_SIZE, addr, next, write, pages, &nr)) break; } else if (is_hugepd(pgdp)) { if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT, addr, next, write, pages, &nr)) break; } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) break; } while (pgdp++, addr = next, addr != end); local_irq_restore(flags); return nr; }
int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { struct mm_struct *mm = current->mm; unsigned long addr, len, end; unsigned long next; pgd_t *pgdp; int nr = 0; pr_devel("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read"); start &= PAGE_MASK; addr = start; len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, start, len))) goto slow_irqon; pr_devel(" aligned: %lx .. %lx\n", start, end); /* * XXX: batch / limit 'nr', to avoid large irq off latency * needs some instrumenting to determine the common sizes used by * important workloads (eg. DB2), and whether limiting the batch size * will decrease performance. * * It seems like we're in the clear for the moment. Direct-IO is * the main guy that batches up lots of get_user_pages, and even * they are limited to 64-at-a-time which is not so many. */ /* * This doesn't prevent pagetable teardown, but does prevent * the pagetables from being freed on powerpc. * * So long as we atomically load page table pointers versus teardown, * we can follow the address down to the the page and take a ref on it. */ local_irq_disable(); pgdp = pgd_offset(mm, addr); do { pgd_t pgd = *pgdp; pr_devel(" %016lx: normal pgd %p\n", addr, (void *)pgd_val(pgd)); next = pgd_addr_end(addr, end); if (pgd_none(pgd)) goto slow; if (pgd_huge(pgd)) { if (!gup_hugepte((pte_t *)pgdp, PGDIR_SIZE, addr, next, write, pages, &nr)) goto slow; } else if (is_hugepd(pgdp)) { if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT, addr, next, write, pages, &nr)) goto slow; } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) goto slow; } while (pgdp++, addr = next, addr != end); local_irq_enable(); VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); return nr; { int ret; slow: local_irq_enable(); slow_irqon: pr_devel(" slow path ! nr = %d\n", nr); /* Try to get the remaining pages with get_user_pages */ start += nr << PAGE_SHIFT; pages += nr; down_read(&mm->mmap_sem); ret = get_user_pages(current, mm, start, (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); up_read(&mm->mmap_sem); /* Have to be a bit careful with return values */ if (nr > 0) { if (ret < 0) ret = nr; else ret += nr; } return ret; } }
int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { struct mm_struct *mm = current->mm; unsigned long addr, len, end; unsigned long next; pgd_t *pgdp; int nr = 0; start &= PAGE_MASK; addr = start; len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len; /* * XXX: batch / limit 'nr', to avoid large irq off latency * needs some instrumenting to determine the common sizes used by * important workloads (eg. DB2), and whether limiting the batch size * will decrease performance. * * It seems like we're in the clear for the moment. Direct-IO is * the main guy that batches up lots of get_user_pages, and even * they are limited to 64-at-a-time which is not so many. */ /* * This doesn't prevent pagetable teardown, but does prevent * the pagetables from being freed on sparc. * * So long as we atomically load page table pointers versus teardown, * we can follow the address down to the the page and take a ref on it. */ local_irq_disable(); pgdp = pgd_offset(mm, addr); do { pgd_t pgd = *pgdp; next = pgd_addr_end(addr, end); if (pgd_none(pgd)) goto slow; if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) goto slow; } while (pgdp++, addr = next, addr != end); local_irq_enable(); VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); return nr; { int ret; slow: local_irq_enable(); /* Try to get the remaining pages with get_user_pages */ start += nr << PAGE_SHIFT; pages += nr; down_read(&mm->mmap_sem); ret = get_user_pages(current, mm, start, (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); up_read(&mm->mmap_sem); /* Have to be a bit careful with return values */ if (nr > 0) { if (ret < 0) ret = nr; else ret += nr; } return ret; } }