From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D47EC4708F for ; Tue, 1 Jun 2021 23:22:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 420DA613CC for ; Tue, 1 Jun 2021 23:22:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 420DA613CC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6EEF46B006E; Tue, 1 Jun 2021 19:22:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 64E2A6B0072; Tue, 1 Jun 2021 19:22:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 403E76B0074; Tue, 1 Jun 2021 19:22:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0076.hostedemail.com [216.40.44.76]) by kanga.kvack.org (Postfix) with ESMTP id 0469C6B006C for ; Tue, 1 Jun 2021 19:22:36 -0400 (EDT) Received: from smtpin39.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 93B916137 for ; Tue, 1 Jun 2021 23:22:36 +0000 (UTC) X-FDA: 78206731512.39.952350F Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf12.hostedemail.com (Postfix) with ESMTP id 1B1463C3 for ; Tue, 1 Jun 2021 23:22:19 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 69192613BC; Tue, 1 Jun 2021 23:22:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622589755; bh=d6j6EDGkhnc+GxiEmiU29Lm/NCKNEqKbXTPVfNJiuuM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ftu0zJj3/weUgRsC8CSXzsmqeuhN2FdlfFbM5ew8+E1xgWmbSx50aC2TeDff/fo3r rXK/4YMRtWDpxZ50xfhXMJM3yljE5igxQ6kcRa58MomH/F5L3TNhL/t884dtSmTIo+ 09ytxS7PJVtcn5dj3yw4PyjcYw2tGvkIVW8OQ6ZWZD48lgYqOpLsFdXQDLWjTH9P85 7oHZbbIgqE5qoxr3gzF+FM4CckTHXQRscojVBqXI2wgPvH8I2utWPqJdlz5LQ+N7pT TM+e02mUxQEZMPM0EBBBYG3z5XlVgjf55p6Q/I8nuq6tynxWktFEIPZ5FcbLpVVNog E77bBQpTQwZTw== From: Ming Lin To: Linus Torvalds , Hugh Dickins , Simon Ser Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ming Lin Subject: [PATCH 2/2] mm: adds NOSIGBUS extension for out-of-band shmem read Date: Tue, 1 Jun 2021 16:22:33 -0700 Message-Id: <1622589753-9206-3-git-send-email-mlin@kernel.org> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1622589753-9206-1-git-send-email-mlin@kernel.org> References: <1622589753-9206-1-git-send-email-mlin@kernel.org> Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ftu0zJj3; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of mlin@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=mlin@kernel.org X-Stat-Signature: 3w6ya9j687i6bsoc45e7n4zoyhhbst1g X-Rspamd-Queue-Id: 1B1463C3 X-Rspamd-Server: rspam02 X-HE-Tag: 1622589739-126602 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: Adds new flag MAP_NOSIGBUS of mmap() to specify the behavior of "don't SIGBUS on read beyond i_size". This flag is only allowed for read only shmem mapping. If you use MAP_NOSIGBUS, and you access pages that don't have a backing store, you will get zero pages, and they will NOT BE SYNCHRONIZED with the backing store possibly later being updated. Any user that uses MAP_NOSIGBUS had better just accept that it's not compatible with expanding the shmem backing store later. Signed-off-by: Ming Lin --- include/linux/mm.h | 2 ++ include/linux/mman.h | 1 + include/uapi/asm-generic/mman-common.h | 1 + mm/mmap.c | 3 +++ mm/shmem.c | 17 ++++++++++++++++- 5 files changed, 23 insertions(+), 1 deletion(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index e9d67bc..5d0e0dc 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -373,6 +373,8 @@ int __add_to_page_cache_locked(struct page *page, struct address_space *mapping, # define VM_UFFD_MINOR VM_NONE #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */ +#define VM_NOSIGBUS VM_FLAGS_BIT(38) /* Do not SIGBUS on out-of-band shmem read */ + /* Bits set in the VMA until the stack is in its final location */ #define VM_STACK_INCOMPLETE_SETUP (VM_RAND_READ | VM_SEQ_READ) diff --git a/include/linux/mman.h b/include/linux/mman.h index b2cbae9..c966b08 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -154,6 +154,7 @@ static inline bool arch_validate_flags(unsigned long flags) _calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) | _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) | _calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) | + _calc_vm_trans(flags, MAP_NOSIGBUS, VM_NOSIGBUS ) | arch_calc_vm_flag_bits(flags); } diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h index f94f65d..55f4be0 100644 --- a/include/uapi/asm-generic/mman-common.h +++ b/include/uapi/asm-generic/mman-common.h @@ -29,6 +29,7 @@ #define MAP_HUGETLB 0x040000 /* create a huge page mapping */ #define MAP_SYNC 0x080000 /* perform synchronous page faults for the mapping */ #define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */ +#define MAP_NOSIGBUS 0x200000 /* do not SIGBUS on out-of-band shmem read */ #define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be * uninitialized */ diff --git a/mm/mmap.c b/mm/mmap.c index 096bba4..69cd856 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1419,6 +1419,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr, if (!len) return -EINVAL; + if ((flags & MAP_NOSIGBUS) && ((prot & PROT_WRITE) || !shmem_file(file))) + return -EINVAL; + /* * Does the application expect PROT_READ to imply PROT_EXEC? * diff --git a/mm/shmem.c b/mm/shmem.c index 5d46611..5d15b08 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1812,7 +1812,22 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, repeat: if (sgp <= SGP_CACHE && ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) { - return -EINVAL; + if (!vma || !(vma->vm_flags & VM_NOSIGBUS)) + return -EINVAL; + + vma->vm_flags |= VM_MIXEDMAP; + /* + * Get zero page for MAP_NOSIGBUS mapping, which isn't + * coherent wrt shmem contents that are expanded and + * filled in later. + */ + error = vm_insert_page(vma, (unsigned long)vmf->address, + ZERO_PAGE(0)); + if (error) + return error; + + *fault_type = VM_FAULT_NOPAGE; + return 0; } sbinfo = SHMEM_SB(inode->i_sb); -- 1.8.3.1