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Tue, 30 Aug 2022 21:18:50 -0700 From: John Hubbard To: Andrew Morton CC: Jens Axboe , Alexander Viro , Miklos Szeredi , Christoph Hellwig , "Darrick J . Wong" , Trond Myklebust , Anna Schumaker , Jan Kara , David Hildenbrand , Logan Gunthorpe , , , , , , LKML , John Hubbard Subject: [PATCH v2 4/7] iov_iter: new iov_iter_pin_pages*() routines Date: Tue, 30 Aug 2022 21:18:40 -0700 Message-ID: <20220831041843.973026-5-jhubbard@nvidia.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220831041843.973026-1-jhubbard@nvidia.com> References: <20220831041843.973026-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: f7e8e07b-7016-4b6f-1204-08da8b07e9af X-MS-TrafficTypeDiagnostic: DM8PR12MB5416:EE_ X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:12.22.5.238;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:InfoNoRecords;CAT:NONE;SFS:(13230016)(4636009)(39860400002)(346002)(136003)(376002)(396003)(46966006)(40470700004)(36840700001)(86362001)(36756003)(82740400003)(41300700001)(36860700001)(107886003)(426003)(1076003)(47076005)(26005)(336012)(2616005)(6666004)(186003)(6916009)(54906003)(40480700001)(82310400005)(70586007)(4326008)(83380400001)(8676002)(316002)(478600001)(7416002)(81166007)(70206006)(40460700003)(356005)(2906002)(8936002)(5660300002)(36900700001);DIR:OUT;SFP:1101; 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dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-Rspamd-Server: rspam02 X-Stat-Signature: rwn3djamsyad91m5zg1ufqcqzo7nqzkf X-Rspamd-Queue-Id: 068FFC0026 X-HE-Tag: 1661919534-391350 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: Provide two new wrapper routines that are intended for user space pages only: iov_iter_pin_pages() iov_iter_pin_pages_alloc() Internally, these routines call pin_user_pages_fast(), instead of get_user_pages_fast(), for user_backed_iter(i) and iov_iter_bvec(i) cases. As always, callers must use unpin_user_pages() or a suitable FOLL_PIN variant, to release the pages, if they actually were acquired via pin_user_pages_fast(). This is a prerequisite to converting bio/block layers over to use pin_user_pages_fast(). Signed-off-by: John Hubbard --- include/linux/uio.h | 4 +++ lib/iov_iter.c | 86 +++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 84 insertions(+), 6 deletions(-) diff --git a/include/linux/uio.h b/include/linux/uio.h index 5896af36199c..e26908e443d1 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -251,6 +251,10 @@ ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages, size_t maxsize, unsigned maxpages, size_t *start); ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages, size_t maxsize, size_t *start); +ssize_t iov_iter_pin_pages(struct iov_iter *i, struct page **pages, + size_t maxsize, unsigned int maxpages, size_t *start); +ssize_t iov_iter_pin_pages_alloc(struct iov_iter *i, struct page ***pages, + size_t maxsize, size_t *start); int iov_iter_npages(const struct iov_iter *i, int maxpages); void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state); diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 4b7fce72e3e5..c63ce0eadfcb 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1425,9 +1425,31 @@ static struct page *first_bvec_segment(const struct iov_iter *i, return page; } +enum pages_alloc_internal_flags { + USE_FOLL_GET, + MAYBE_USE_FOLL_PIN +}; + +/* + * Pins pages, either via get_page(), or via pin_user_page*(). The caller is + * responsible for tracking which pinning mechanism was used here, and releasing + * pages via the appropriate call: put_page() or unpin_user_page(). + * + * The way to figure that out is: + * + * a) If how_to_pin == FOLL_GET, then this routine will always pin via + * get_page(). + * + * b) If how_to_pin == MAYBE_USE_FOLL_PIN, then this routine will pin via + * pin_user_page*() for either user_backed_iter(i) cases, or + * iov_iter_is_bvec(i) cases. However, for the other cases (pipe, + * xarray), pages will be pinned via get_page(). + */ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages, size_t maxsize, - unsigned int maxpages, size_t *start) + unsigned int maxpages, size_t *start, + enum pages_alloc_internal_flags how_to_pin) + { unsigned int n; @@ -1454,7 +1476,12 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, n = want_pages_array(pages, maxsize, *start, maxpages); if (!n) return -ENOMEM; - res = get_user_pages_fast(addr, n, gup_flags, *pages); + + if (how_to_pin == MAYBE_USE_FOLL_PIN) + res = pin_user_pages_fast(addr, n, gup_flags, *pages); + else + res = get_user_pages_fast(addr, n, gup_flags, *pages); + if (unlikely(res <= 0)) return res; maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start); @@ -1470,8 +1497,13 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, if (!n) return -ENOMEM; p = *pages; - for (int k = 0; k < n; k++) - get_page(p[k] = page + k); + for (int k = 0; k < n; k++) { + p[k] = page + k; + if (how_to_pin == MAYBE_USE_FOLL_PIN) + pin_user_page(p[k]); + else + get_page(p[k]); + } maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start); i->count -= maxsize; i->iov_offset += maxsize; @@ -1497,10 +1529,29 @@ ssize_t iov_iter_get_pages2(struct iov_iter *i, return 0; BUG_ON(!pages); - return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start); + return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start, + USE_FOLL_GET); } EXPORT_SYMBOL(iov_iter_get_pages2); +/* + * A FOLL_PIN variant that calls pin_user_pages_fast() instead of + * get_user_pages_fast(). + */ +ssize_t iov_iter_pin_pages(struct iov_iter *i, + struct page **pages, size_t maxsize, unsigned int maxpages, + size_t *start) +{ + if (!maxpages) + return 0; + if (WARN_ON_ONCE(!pages)) + return -EINVAL; + + return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start, + MAYBE_USE_FOLL_PIN); +} +EXPORT_SYMBOL(iov_iter_pin_pages); + ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages, size_t maxsize, size_t *start) @@ -1509,7 +1560,8 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, *pages = NULL; - len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start); + len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start, + USE_FOLL_GET); if (len <= 0) { kvfree(*pages); *pages = NULL; @@ -1518,6 +1570,28 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, } EXPORT_SYMBOL(iov_iter_get_pages_alloc2); +/* + * A FOLL_PIN variant that calls pin_user_pages_fast() instead of + * get_user_pages_fast(). + */ +ssize_t iov_iter_pin_pages_alloc(struct iov_iter *i, + struct page ***pages, size_t maxsize, + size_t *start) +{ + ssize_t len; + + *pages = NULL; + + len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start, + MAYBE_USE_FOLL_PIN); + if (len <= 0) { + kvfree(*pages); + *pages = NULL; + } + return len; +} +EXPORT_SYMBOL(iov_iter_pin_pages_alloc); + size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i) {