[resend,mm,net-next,2/3] mm: Add vm_insert_pages().

Message ID	20200128025958.43490-2-arjunroy.kdev@gmail.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <SRS0=ZB1i=3R=kvack.org=owner-linux-mm@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B095E2173E From: Arjun Roy <arjunroy.kdev@gmail.com> To: davem@davemloft.net, netdev@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org Cc: arjunroy@google.com, Eric Dumazet <edumazet@google.com>, Soheil Hassas Yeganeh <soheil@google.com> Subject: [PATCH resend mm,net-next 2/3] mm: Add vm_insert_pages(). Date: Mon, 27 Jan 2020 18:59:57 -0800 Message-Id: <20200128025958.43490-2-arjunroy.kdev@gmail.com> In-Reply-To: <20200128025958.43490-1-arjunroy.kdev@gmail.com> References: <20200128025958.43490-1-arjunroy.kdev@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	[resend,mm,net-next,1/3] mm: Refactor insert_page to prepare for batched-lock insert. \| expand [resend,mm,net-next,1/3] mm: Refactor insert_page to prepare for batched-lock insert. [resend,mm,net-next,2/3] mm: Add vm_insert_pages(). [resend,mm,net-next,3/3] net-zerocopy: Use vm_insert_pages() for tcp rcv zerocopy.

diff --git a/include/linux/mm.h b/include/linux/mm.h index 29c928ba6b42..a3ac40fbe8fd 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2563,6 +2563,8 @@ struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr); int remap_pfn_range(struct vm_area_struct *, unsigned long addr, unsigned long pfn, unsigned long size, pgprot_t); int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *); +int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num); int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn); int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, diff --git a/mm/memory.c b/mm/memory.c index 7e23a9275386..1655c5feaf32 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1670,8 +1670,7 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address, } EXPORT_SYMBOL_GPL(zap_vma_ptes); -pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, - spinlock_t **ptl) +static pmd_t *walk_to_pmd(struct mm_struct *mm, unsigned long addr) { pgd_t *pgd; p4d_t *p4d; @@ -1690,6 +1689,16 @@ pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, return NULL; VM_BUG_ON(pmd_trans_huge(*pmd)); + return pmd; +} + +pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr, + spinlock_t **ptl) +{ + pmd_t *pmd = walk_to_pmd(mm, addr); + + if (!pmd) + return NULL; return pte_alloc_map_lock(mm, pmd, addr, ptl); } @@ -1714,6 +1723,15 @@ static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte, return 0; } +static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd, + unsigned long addr, struct page *page, pgprot_t prot) +{ + const int err = validate_page_before_insert(page); + + return err ? err : insert_page_into_pte_locked( + mm, pte_offset_map(pmd, addr), addr, page, prot); +} + /* * This is the old fallback for page remapping. * @@ -1742,6 +1760,95 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr, return retval; } +/* insert_pages() amortizes the cost of spinlock operations + * when inserting pages in a loop. + */ +static int insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num, pgprot_t prot) +{ + pmd_t *pmd = NULL; + spinlock_t *pte_lock = NULL; + struct mm_struct *const mm = vma->vm_mm; + unsigned long curr_page_idx = 0; + unsigned long remaining_pages_total = *num; + unsigned long pages_to_write_in_pmd; + int ret; +more: + ret = -EFAULT; + pmd = walk_to_pmd(mm, addr); + if (!pmd) + goto out; + + pages_to_write_in_pmd = min_t(unsigned long, + remaining_pages_total, PTRS_PER_PTE - pte_index(addr)); + + /* Allocate the PTE if necessary; takes PMD lock once only. */ + ret = -ENOMEM; + if (pte_alloc(mm, pmd, addr)) + goto out; + pte_lock = pte_lockptr(mm, pmd); + + while (pages_to_write_in_pmd) { + int pte_idx = 0; + const int batch_size = min_t(int, pages_to_write_in_pmd, 8); + + spin_lock(pte_lock); + for (; pte_idx < batch_size; ++pte_idx) { + int err = insert_page_in_batch_locked(mm, pmd, + addr, pages[curr_page_idx], prot); + if (unlikely(err)) { + spin_unlock(pte_lock); + ret = err; + remaining_pages_total -= pte_idx; + goto out; + } + addr += PAGE_SIZE; + ++curr_page_idx; + } + spin_unlock(pte_lock); + pages_to_write_in_pmd -= batch_size; + remaining_pages_total -= batch_size; + } + if (remaining_pages_total) + goto more; + ret = 0; +out: + *num = remaining_pages_total; + return ret; +} + +/** + * vm_insert_pages - insert multiple pages into user vma, batching the pmd lock. + * @vma: user vma to map to + * @addr: target start user address of these pages + * @pages: source kernel pages + * @num: in: number of pages to map. out: number of pages that were *not* + * mapped. (0 means all pages were successfully mapped). + * + * Preferred over vm_insert_page() when inserting multiple pages. + * + * In case of error, we may have mapped a subset of the provided + * pages. It is the caller's responsibility to account for this case. + * + * The same restrictions apply as in vm_insert_page(). + */ +int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr, + struct page **pages, unsigned long *num) +{ + const unsigned long end_addr = addr + (*num * PAGE_SIZE) - 1; + + if (addr < vma->vm_start || end_addr >= vma->vm_end) + return -EFAULT; + if (!(vma->vm_flags & VM_MIXEDMAP)) { + BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem)); + BUG_ON(vma->vm_flags & VM_PFNMAP); + vma->vm_flags |= VM_MIXEDMAP; + } + /* Defer page refcount checking till we're about to map that page. */ + return insert_pages(vma, addr, pages, num, vma->vm_page_prot); +} +EXPORT_SYMBOL(vm_insert_pages); + /** * vm_insert_page - insert single page into user vma * @vma: user vma to map to

[resend,mm,net-next,2/3] mm: Add vm_insert_pages().

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