From patchwork Mon Mar 27 17:45:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Matthew Wilcox (Oracle)" X-Patchwork-Id: 13189762 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B7BDC77B61 for ; Mon, 27 Mar 2023 17:45:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229498AbjC0Rpg (ORCPT ); Mon, 27 Mar 2023 13:45:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231820AbjC0Rpc (ORCPT ); Mon, 27 Mar 2023 13:45:32 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49280199E; Mon, 27 Mar 2023 10:45:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=sN2jldM9CY7aIkWwKeR1CK1+RammERB2ANKihvDELc4=; b=qZecYoGcykBbwmr7BQ73lsvQRL 7gZkBAEKJXtSnbFL1+kjXtQ9/BHx6ug9L2v458DCOq4fkXkxqUuFJ4CZ5M7L/GVgnHcLBQYhRBFC6 QWrfg+YCRq5wnEsDCbLZUN4kZSYirKyVwj0+KdtHTIXuD0om2HYLsfQhgcHrgVOgs5juAvishtQp0 VhctSXw8l3NyR8zrorbrBrgVMmqTFpSm2Bpvfy4H2Z4hLc7Jx5L4AmO8o6wcHhHgc8w7HvEUhJ24D 3Z9ZT4zFFIjhtTwiayCAFm1+6tWK5MycDRBzmsaxNAciKbdsiMxohtdQWGGc15DRYTUAP47SaXfGj Dspc/OhA==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pgquI-007bGY-FT; Mon, 27 Mar 2023 17:45:22 +0000 From: "Matthew Wilcox (Oracle)" To: Andrew Morton Cc: "Matthew Wilcox (Oracle)" , linux-xfs@vger.kernel.org, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 3/3] mm: Hold the RCU read lock over calls to ->map_pages Date: Mon, 27 Mar 2023 18:45:15 +0100 Message-Id: <20230327174515.1811532-4-willy@infradead.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20230327174515.1811532-1-willy@infradead.org> References: <20230327174515.1811532-1-willy@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org Prevent filesystems from doing things which sleep in their map_pages method. This is in preparation for a pagefault path protected only by RCU. Signed-off-by: Matthew Wilcox (Oracle) --- Documentation/filesystems/locking.rst | 4 ++-- mm/memory.c | 11 ++++++++--- 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 922886fefb7f..8a80390446ba 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -645,7 +645,7 @@ ops mmap_lock PageLocked(page) open: yes close: yes fault: yes can return with page locked -map_pages: yes +map_pages: read page_mkwrite: yes can return with page locked pfn_mkwrite: yes access: yes @@ -661,7 +661,7 @@ locked. The VM will unlock the page. ->map_pages() is called when VM asks to map easy accessible pages. Filesystem should find and map pages associated with offsets from "start_pgoff" -till "end_pgoff". ->map_pages() is called with page table locked and must +till "end_pgoff". ->map_pages() is called with the RCU lock held and must not block. If it's not possible to reach a page without blocking, filesystem should skip it. Filesystem should use set_pte_range() to setup page table entry. Pointer to entry associated with the page is passed in diff --git a/mm/memory.c b/mm/memory.c index 8071bb17abf2..a7edf6d714db 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4461,6 +4461,7 @@ static vm_fault_t do_fault_around(struct vm_fault *vmf) /* The page offset of vmf->address within the VMA. */ pgoff_t vma_off = vmf->pgoff - vmf->vma->vm_pgoff; pgoff_t from_pte, to_pte; + vm_fault_t ret; /* The PTE offset of the start address, clamped to the VMA. */ from_pte = max(ALIGN_DOWN(pte_off, nr_pages), @@ -4476,9 +4477,13 @@ static vm_fault_t do_fault_around(struct vm_fault *vmf) return VM_FAULT_OOM; } - return vmf->vma->vm_ops->map_pages(vmf, - vmf->pgoff + from_pte - pte_off, - vmf->pgoff + to_pte - pte_off); + rcu_read_lock(); + ret = vmf->vma->vm_ops->map_pages(vmf, + vmf->pgoff + from_pte - pte_off, + vmf->pgoff + to_pte - pte_off); + rcu_read_unlock(); + + return ret; } /* Return true if we should do read fault-around, false otherwise */