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[86.156.84.164]) by smtp.googlemail.com with ESMTPSA id f18-20020a05600c155200b003ede2c59a54sm1416952wmg.37.2023.03.23.03.15.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Mar 2023 03:15:25 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Baoquan He , Uladzislau Rezki , Matthew Wilcox , David Hildenbrand , Liu Shixin , Jiri Olsa , Jens Axboe , Alexander Viro , Lorenzo Stoakes Subject: [PATCH v8 3/4] iov_iter: add copy_page_to_iter_nofault() Date: Thu, 23 Mar 2023 10:15:18 +0000 Message-Id: <19734729defb0f498a76bdec1bef3ac48a3af3e8.1679566220.git.lstoakes@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 3A6B21C002D X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: frqp5yhj4mufpmtjqy66gf8r9c1xi9yw X-HE-Tag: 1679566527-604881 X-HE-Meta: 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 Y0FvYdMP 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 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 a means to copy a page to user space from an iterator, aborting if a page fault would occur. This supports compound pages, but may be passed a tail page with an offset extending further into the compound page, so we cannot pass a folio. This allows for this function to be called from atomic context and _try_ to user pages if they are faulted in, aborting if not. The function does not use _copy_to_iter() in order to not specify might_fault(), this is similar to copy_page_from_iter_atomic(). This is being added in order that an iteratable form of vread() can be implemented while holding spinlocks. Signed-off-by: Lorenzo Stoakes --- include/linux/uio.h | 2 ++ lib/iov_iter.c | 48 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+) diff --git a/include/linux/uio.h b/include/linux/uio.h index 27e3fd942960..29eb18bb6feb 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -173,6 +173,8 @@ static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset, { return copy_page_to_iter(&folio->page, offset, bytes, i); } +size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, + size_t bytes, struct iov_iter *i); static __always_inline __must_check size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 274014e4eafe..34dd6bdf2fba 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -172,6 +172,18 @@ static int copyout(void __user *to, const void *from, size_t n) return n; } +static int copyout_nofault(void __user *to, const void *from, size_t n) +{ + long res; + + if (should_fail_usercopy()) + return n; + + res = copy_to_user_nofault(to, from, n); + + return res < 0 ? n : res; +} + static int copyin(void *to, const void __user *from, size_t n) { size_t res = n; @@ -734,6 +746,42 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, } EXPORT_SYMBOL(copy_page_to_iter); +size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, size_t bytes, + struct iov_iter *i) +{ + size_t res = 0; + + if (!page_copy_sane(page, offset, bytes)) + return 0; + if (WARN_ON_ONCE(i->data_source)) + return 0; + if (unlikely(iov_iter_is_pipe(i))) + return copy_page_to_iter_pipe(page, offset, bytes, i); + page += offset / PAGE_SIZE; // first subpage + offset %= PAGE_SIZE; + while (1) { + void *kaddr = kmap_local_page(page); + size_t n = min(bytes, (size_t)PAGE_SIZE - offset); + + iterate_and_advance(i, n, base, len, off, + copyout_nofault(base, kaddr + offset + off, len), + memcpy(base, kaddr + offset + off, len) + ) + kunmap_local(kaddr); + res += n; + bytes -= n; + if (!bytes || !n) + break; + offset += n; + if (offset == PAGE_SIZE) { + page++; + offset = 0; + } + } + return res; +} +EXPORT_SYMBOL(copy_page_to_iter_nofault); + size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes, struct iov_iter *i) { -- 2.39.2