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Tue, 20 Aug 2019 21:07:33 -0700 From: John Hubbard To: Andrew Morton CC: Christoph Hellwig , Dan Williams , Dave Chinner , Ira Weiny , Jan Kara , Jason Gunthorpe , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Vlastimil Babka , LKML , , , , John Hubbard Subject: [PATCH v2 1/3] For Ira: tiny formatting tweak to kerneldoc Date: Tue, 20 Aug 2019 21:07:25 -0700 Message-ID: <20190821040727.19650-2-jhubbard@nvidia.com> X-Mailer: git-send-email 2.22.1 In-Reply-To: <20190821040727.19650-1-jhubbard@nvidia.com> References: <20190821040727.19650-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1566360454; bh=N6ccyzf5PMKW+koaJVWa/WJ5yd4Gtcd+1v71ttVDCNg=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=kyATeI4GvI0wM6LrUvgYcUuvVkygFA4JyTgW+0ZbIfoMphOLUP79l03d3VBYHsz2s 1CY7+MAZotjRlkUZf+gs3dpdA2mi38fNQj7WAuTHr35cgt5F0ODZXtOnG4BQ0KpeKy mx3iRvuI/rW4Jfnk/+2cwoElnxfMi8e4QwgNR5vbt3BQKBCNfotmHIM//RX1LyEPOW DHW1oHlGkyqC4At7gax4YXMnfwFq5jRR/YEsU8tlZ/yOAhWfATtCG5Okf20bfeGKGU w9byaMIBr4MVxT8h+4jI9vhBtdxj/dXbu80/v5ryCzlKcjbcNAi36pz6ZKsNKOwKvV ugMEds1/mnrEQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: For your vaddr_pin_pages() and vaddr_unpin_pages(). Just merge it into wherever it goes please. Didn't want to cause merge problems so it's a separate patch-let. Signed-off-by: John Hubbard --- mm/gup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 56421b880325..e49096d012ea 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2465,7 +2465,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, EXPORT_SYMBOL_GPL(get_user_pages_fast); /** - * vaddr_pin_pages pin pages by virtual address and return the pages to the + * vaddr_pin_pages() - pin pages by virtual address and return the pages to the * user. * * @addr: start address @@ -2505,7 +2505,7 @@ long vaddr_pin_pages(unsigned long addr, unsigned long nr_pages, EXPORT_SYMBOL(vaddr_pin_pages); /** - * vaddr_unpin_pages - counterpart to vaddr_pin_pages + * vaddr_unpin_pages() - counterpart to vaddr_pin_pages * * @pages: array of pages returned * @nr_pages: number of pages in pages From patchwork Wed Aug 21 04:07:26 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11105401 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 16BA11805 for ; 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Tue, 20 Aug 2019 21:07:33 -0700 From: John Hubbard To: Andrew Morton CC: Christoph Hellwig , Dan Williams , Dave Chinner , Ira Weiny , Jan Kara , Jason Gunthorpe , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Vlastimil Babka , LKML , , , , John Hubbard , "Michal Hocko" Subject: [PATCH v2 2/3] mm/gup: introduce FOLL_PIN flag for get_user_pages() Date: Tue, 20 Aug 2019 21:07:26 -0700 Message-ID: <20190821040727.19650-3-jhubbard@nvidia.com> X-Mailer: git-send-email 2.22.1 In-Reply-To: <20190821040727.19650-1-jhubbard@nvidia.com> References: <20190821040727.19650-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1566360455; bh=vXTR5X576mO9cmS9xl7R7KR9+U7vJV56myFxKqNBdTs=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=RJvMkiak0tzTwcCSvp33yG5WfqF9U4NOaOCVMZ5uYvRXjYdZi+/K97QTPP5ZrURvK 6pM2OKGy8zZc3UvMYlHiZkLqER5IcaSP6qs5SX9frmczNM5fEsm3U952K6yieeJwc3 51cP+GTW5WHrvhwdEl1aAW5PFlfR8EpZTqS/ZpX6Xbm+WNCXL24HWIcIdXQpMsUIzE D0mk89PmNnLoQ/PfiZYEPVRLmXeFy0q8pSqg+ZRSmJrlnOZOlOeqEm+z1UmZtcCw4b cuYh/n9t7lihEjNuAsyxPqaxrYCf5IK9OEPa4qnFsT2qQNmjWR/kFrIpk0teDK7KAa C/pGQVF0bsKTQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: As explained in the newly added documentation for FOLL_PIN and FOLL_LONGTERM, in every case where vaddr_pin_pages() is required, FOLL_PIN must be set. That reason, plus a desire to keep FOLL_PIN an internal (to get_user_pages() and follow_page()) detail, is why vaddr_pin_pages() sets FOLL_PIN. FOLL_LONGTERM, on the other hand, in only set in *some* cases, but not all. For that reason, this patch moves the setting of FOLL_LONGTERM out to the caller. Also add fairly extensive documentation of the meaning and use of both FOLL_PIN and FOLL_LONGTERM. Thanks to Jan Kara and Vlastimil Babka for explaining the 4 cases in this documentation. (I've reworded it and expanded on it slightly.) The motivation behind moving away from "bare" get_user_pages() calls is described in more detail in commit fc1d8e7cca2d ("mm: introduce put_user_page*(), placeholder versions"). Cc: Vlastimil Babka Cc: Jan Kara Cc: Michal Hocko Cc: Ira Weiny Signed-off-by: John Hubbard --- drivers/infiniband/core/umem.c | 1 + include/linux/mm.h | 56 ++++++++++++++++++++++++++++++---- mm/gup.c | 2 +- 3 files changed, 52 insertions(+), 7 deletions(-) diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c index e69eecb0023f..d84f1bfb8d21 100644 --- a/drivers/infiniband/core/umem.c +++ b/drivers/infiniband/core/umem.c @@ -300,6 +300,7 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr, while (npages) { down_read(&mm->mmap_sem); + gup_flags |= FOLL_LONGTERM; ret = vaddr_pin_pages(cur_base, min_t(unsigned long, npages, PAGE_SIZE / sizeof (struct page *)), diff --git a/include/linux/mm.h b/include/linux/mm.h index bc675e94ddf8..6e7de424bf5e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2644,6 +2644,8 @@ static inline vm_fault_t vmf_error(int err) struct page *follow_page(struct vm_area_struct *vma, unsigned long address, unsigned int foll_flags); +/* Flags for follow_page(), get_user_pages ("GUP"), and vaddr_pin_pages(): */ + #define FOLL_WRITE 0x01 /* check pte is writable */ #define FOLL_TOUCH 0x02 /* mark page accessed */ #define FOLL_GET 0x04 /* do get_page on page */ @@ -2663,13 +2665,15 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_ANON 0x8000 /* don't do file mappings */ #define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */ #define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ +#define FOLL_PIN 0x40000 /* pages must be released via put_user_page() */ /* - * NOTE on FOLL_LONGTERM: + * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each + * other. Here is what they mean, and how to use them: * * FOLL_LONGTERM indicates that the page will be held for an indefinite time - * period _often_ under userspace control. This is contrasted with - * iov_iter_get_pages() where usages which are transient. + * period _often_ under userspace control. This is in contrast to + * iov_iter_get_pages(), where usages which are transient. * * FIXME: For pages which are part of a filesystem, mappings are subject to the * lifetime enforced by the filesystem and we need guarantees that longterm @@ -2684,11 +2688,51 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, * Currently only get_user_pages() and get_user_pages_fast() support this flag * and calls to get_user_pages_[un]locked are specifically not allowed. This * is due to an incompatibility with the FS DAX check and - * FAULT_FLAG_ALLOW_RETRY + * FAULT_FLAG_ALLOW_RETRY. * - * In the CMA case: longterm pins in a CMA region would unnecessarily fragment - * that region. And so CMA attempts to migrate the page before pinning when + * In the CMA case: long term pins in a CMA region would unnecessarily fragment + * that region. And so, CMA attempts to migrate the page before pinning, when * FOLL_LONGTERM is specified. + * + * FOLL_PIN indicates that a special kind of tracking (not just page->_refcount, + * but an additional pin counting system) will be invoked. This is intended for + * anything that gets a page reference and then touches page data (for example, + * Direct IO). This lets the filesystem know that some non-file-system entity is + * potentially changing the pages' data. FOLL_PIN pages must be released, + * ultimately, by a call to put_user_page(). Typically that will be via one of + * the vaddr_unpin_pages() variants. + * + * FIXME: note that this special tracking is not in place yet. However, the + * pages should still be released by put_user_page(). + * + * When and where to use each flag: + * + * CASE 1: Direct IO (DIO). There are GUP references to pages that are serving + * as DIO buffers. These buffers are needed for a relatively short time (so they + * are not "long term"). No special synchronization with page_mkclean() or + * munmap() is provided. Therefore, flags to set at the call site are: + * + * FOLL_PIN + * + * CASE 2: RDMA. There are GUP references to pages that are serving as DMA + * buffers. These buffers are needed for a long time ("long term"). No special + * synchronization with page_mkclean() or munmap() is provided. Therefore, flags + * to set at the call site are: + * + * FOLL_PIN | FOLL_LONGTERM + * + * There is also a special case when the pages are DAX pages: in addition to the + * above flags, the caller needs a file lease. This is provided via the struct + * vaddr_pin argument to vaddr_pin_pages(). + * + * CASE 3: ODP (Mellanox/Infiniband On Demand Paging: the hardware supports + * replayable page faulting). There are GUP references to pages serving as DMA + * buffers. For ODP, MMU notifiers are used to synchronize with page_mkclean() + * and munmap(). Therefore, normal GUP calls are sufficient, so neither flag + * needs to be set. + * + * CASE 4: pinning for struct page manipulation only. Here, normal GUP calls are + * sufficient, so neither flag needs to be set. */ static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags) diff --git a/mm/gup.c b/mm/gup.c index e49096d012ea..ba316d960d7a 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2490,7 +2490,7 @@ long vaddr_pin_pages(unsigned long addr, unsigned long nr_pages, { long ret; - gup_flags |= FOLL_LONGTERM; + gup_flags |= FOLL_PIN; if (!vaddr_pin || (!vaddr_pin->mm && !vaddr_pin->f_owner)) return -EINVAL; From patchwork Wed Aug 21 04:07:27 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11105405 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3673F1813 for ; Wed, 21 Aug 2019 04:07:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E9E30206BA for ; 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Tue, 20 Aug 2019 21:07:33 -0700 From: John Hubbard To: Andrew Morton CC: Christoph Hellwig , Dan Williams , Dave Chinner , Ira Weiny , Jan Kara , Jason Gunthorpe , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Vlastimil Babka , LKML , , , , John Hubbard Subject: [PATCH v2 3/3] mm/gup: introduce vaddr_pin_pages_remote(), and invoke it Date: Tue, 20 Aug 2019 21:07:27 -0700 Message-ID: <20190821040727.19650-4-jhubbard@nvidia.com> X-Mailer: git-send-email 2.22.1 In-Reply-To: <20190821040727.19650-1-jhubbard@nvidia.com> References: <20190821040727.19650-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1566360454; bh=yaS48N2o2CPvqMWzUWhpSpOm4JNtAfActS1Th7wctzE=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=qUOBGoJIEf/YL08oCTcD4iSkBMJKo16mo4WSO2uW9Tcw8WKfd/nCAvDlVcUPKWCNP Z8ZgbCOK0B2mKWctwfX3z0PsDzknh2dJF+WCT+ZUaDmv055HjoS1XzCjVmsC6tOxq+ cm/0B4U9iyKnl+GKGAAYdhgqzxvQju0MNYSprL2O16ZJrKl9ELPyKIyrjzVtIy73eB /SCUMKsMJVqoEMLZGyud5/rFqD2njRVbT+8DSl9Za/uWEWrDvphikno0VX7t4VZx4U PNsDCO0gp7taqzGYS1hizU+vuZMc2c+h7C+EDcp9KG8QhNUiIZEt/1ppoCRsXfGzJH 1EdKGW5PtlAbw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: vaddr_pin_user_pages_remote() is the "vaddr_pin_pages" corresponding variant to get_user_pages_remote(), except that: a) it sets FOLL_PIN, and b) it can handle FOLL_LONGTERM (and the associated vaddr_pin arg). Change process_vm_rw_single_vec() to invoke the new function. Signed-off-by: John Hubbard Cc: Ira Weiny --- include/linux/mm.h | 5 +++++ mm/gup.c | 34 ++++++++++++++++++++++++++++++++++ mm/process_vm_access.c | 23 +++++++++++++---------- 3 files changed, 52 insertions(+), 10 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6e7de424bf5e..849b509e9f89 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1606,6 +1606,11 @@ int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, long vaddr_pin_pages(unsigned long addr, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, struct vaddr_pin *vaddr_pin); +long vaddr_pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked, + struct vaddr_pin *vaddr_pin); void vaddr_unpin_pages(struct page **pages, unsigned long nr_pages, struct vaddr_pin *vaddr_pin, bool make_dirty); bool mapping_inode_has_layout(struct vaddr_pin *vaddr_pin, struct page *page); diff --git a/mm/gup.c b/mm/gup.c index ba316d960d7a..d713ed9d4b9a 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2522,3 +2522,37 @@ void vaddr_unpin_pages(struct page **pages, unsigned long nr_pages, __put_user_pages_dirty_lock(pages, nr_pages, make_dirty, vaddr_pin); } EXPORT_SYMBOL(vaddr_unpin_pages); + +/** + * vaddr_pin_user_pages_remote() - pin pages by virtual address and return the + * pages to the user. + * + * @tsk: the task_struct to use for page fault accounting, or + * NULL if faults are not to be recorded. + * @mm: mm_struct of target mm + * @addr: start address + * @nr_pages: number of pages to pin + * @gup_flags: flags to use for the pin. Please see FOLL_* documentation in + * mm.h. + * @pages: array of pages returned + * @vaddr_pin: If FOLL_LONGTERM is set, then vaddr_pin should point to an + * initialized struct that contains the owning mm and file. Otherwise, vaddr_pin + * should be set to NULL. + * + * This is the "vaddr_pin_pages" corresponding variant to + * get_user_pages_remote(), except that: + * a) it sets FOLL_PIN, and + * b) it can handle FOLL_LONGTERM (and the associated vaddr_pin arg). + */ +long vaddr_pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked, + struct vaddr_pin *vaddr_pin) +{ + gup_flags |= FOLL_TOUCH | FOLL_REMOTE | FOLL_PIN; + + return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas, + locked, gup_flags, vaddr_pin); +} +EXPORT_SYMBOL(vaddr_pin_user_pages_remote); diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c index 357aa7bef6c0..28e0a17b6080 100644 --- a/mm/process_vm_access.c +++ b/mm/process_vm_access.c @@ -44,7 +44,6 @@ static int process_vm_rw_pages(struct page **pages, if (vm_write) { copied = copy_page_from_iter(page, offset, copy, iter); - set_page_dirty_lock(page); } else { copied = copy_page_to_iter(page, offset, copy, iter); } @@ -96,7 +95,7 @@ static int process_vm_rw_single_vec(unsigned long addr, flags |= FOLL_WRITE; while (!rc && nr_pages && iov_iter_count(iter)) { - int pages = min(nr_pages, max_pages_per_loop); + int pinned_pages = min(nr_pages, max_pages_per_loop); int locked = 1; size_t bytes; @@ -106,14 +105,17 @@ static int process_vm_rw_single_vec(unsigned long addr, * current/current->mm */ down_read(&mm->mmap_sem); - pages = get_user_pages_remote(task, mm, pa, pages, flags, - process_pages, NULL, &locked); + + pinned_pages = vaddr_pin_user_pages_remote(task, mm, pa, + pinned_pages, flags, + process_pages, NULL, + &locked, NULL); if (locked) up_read(&mm->mmap_sem); - if (pages <= 0) + if (pinned_pages <= 0) return -EFAULT; - bytes = pages * PAGE_SIZE - start_offset; + bytes = pinned_pages * PAGE_SIZE - start_offset; if (bytes > len) bytes = len; @@ -122,10 +124,11 @@ static int process_vm_rw_single_vec(unsigned long addr, vm_write); len -= bytes; start_offset = 0; - nr_pages -= pages; - pa += pages * PAGE_SIZE; - while (pages) - put_page(process_pages[--pages]); + nr_pages -= pinned_pages; + pa += pinned_pages * PAGE_SIZE; + + /* If vm_write is set, the pages need to be made dirty: */ + vaddr_unpin_pages(process_pages, pinned_pages, NULL, vm_write); } return rc;