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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5CCDAD0EE13 for ; Tue, 25 Nov 2025 18:39:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BB9E36B00AA; Tue, 25 Nov 2025 13:39:10 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B42FC6B00B6; Tue, 25 Nov 2025 13:39:10 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A806B6B00B7; Tue, 25 Nov 2025 13:39:10 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 966C76B00AA for ; Tue, 25 Nov 2025 13:39:10 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 28C26160396 for ; Tue, 25 Nov 2025 18:39:10 +0000 (UTC) X-FDA: 84149991660.13.94F901C Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf15.hostedemail.com (Postfix) with ESMTP id 9BE0FA000F for ; Tue, 25 Nov 2025 18:39:08 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=k+rjAQwX; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf15.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764095948; a=rsa-sha256; cv=none; b=ygZsM8N+zS1AE4LcG+3fGu6rumtfDKJb8f6Y8AXU65fratl4UWgCgLsnvo+Yx/YAMltAnI 15U/Hm3a0wGF77byDToLoHrslZyAN/wP9mNu8SXgUGtHVtVY9u04ovSvGbmeq8kyAszt2/ jXNpJykrUi1Ws7wyc0askI4/SCBWQnY= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=k+rjAQwX; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf15.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1764095948; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Ws77kLN5WtsBEeQFN8jqfnnTDH3q/qyhmVOzeaEJjTc=; b=JRq9UX+ekKZva3AV3pfKgakjouzof1gEb1qPfoleY0IdtmWNq34ZWRhPib2zdhMNnXP+95 IFPt2mKDOCDgTjGDrT8yV3f+rJHAmocqvlRSwXbq/NVje/upDK4hAHz4QTNBINE+iQN98S oOmjv9nGZryh/ji7fpopf48vGWXiRho= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 9EA896013D; Tue, 25 Nov 2025 18:39:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E139DC19422; Tue, 25 Nov 2025 18:39:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764095947; bh=OMs5feUckVCg3jntuqU22gZ/ufy0V9GaFPtJ4+nCsbQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k+rjAQwX+9oyD23In9ooJMuiZlgSjVe7F3a6uIEgz1GZ4RWJmAVwRq1A3GX0F11g8 WpbUvXAxGYRUz92F99Q31i/6oM4ExJUMNRmsybLKQme98QngVmtlLHeXJ8Td9Av+WA lR1AWyV+or429S5CqW7LTi+L5VVrghZlv+Hv9eOyXNrWjN4+Jv6fllrLCy+6dK4hXc J7LSRDv/TDGREvUaiVhFkFF6O5aSi9KW8pDWeVgykB4wU5N6LDOWfpObOmg2NG3s+h 4HxcYX0LT2C8ThnZbwWmQvS81JGFvtbFBrzs9A8Or9xTaLwr1yR1MLPG9UB8ZBlWMc qhMk5fLNWc7mw== From: Mike Rapoport To: linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Axel Rasmussen , Baolin Wang , David Hildenbrand , Hugh Dickins , James Houghton , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Nikita Kalyazin , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, "David Hildenbrand (Red Hat)" Subject: [PATCH v2 3/5] mm: introduce VM_FAULT_UFFD_MINOR fault reason Date: Tue, 25 Nov 2025 20:38:38 +0200 Message-ID: <20251125183840.2368510-4-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251125183840.2368510-1-rppt@kernel.org> References: <20251125183840.2368510-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9BE0FA000F X-Stat-Signature: cj5cj4z8h1ramg9io7x6umhzsj13rug5 X-Rspam-User: X-HE-Tag: 1764095948-910269 X-HE-Meta: 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 wGpoZyEN CHNKxS+kxxp5OSQe0SjbrT7XFGWD7bikAFn2ronsUb8D1sdkIUPr/+rYjZPYfk+c5lknIqmzZaZ72Xy6W7FXBqpdAKvKfOy+Q/cTev6cpD9mwtWomBRmxWrTcreAwXQnAVRkdCUZoVmRE7gZZ6xCHnXVmdvcEy1/lDQp+8+/i8pNS9l7KLe3WNKMZbe7WfhNbqdMUFv8anpPOaIIFfuk2yUwYkHpbX8c0wccxwlt2Q/o2CMhU/YAtlUpMAIE7rrLo6y0zXcJ5WIHrY/VgZBKcJhu/KCigWtjVWfKxnV5UcaH36b4EpEtPVFOX57pj3sGHADYo 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: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" When a VMA is registered with userfaulfd in minor mode, its ->fault() method should check if a folio exists in the page cache and if yes ->fault() should call handle_userfault(VM_UFFD_MISSING). Instead of calling handle_userfault() directly from a specific ->fault() implementation introduce new fault reason VM_FAULT_UFFD_MINOR that will notify the core page fault handler that it should call handle_userfaultfd(VM_UFFD_MISSING) to complete a page fault. Replace a call to handle_userfault(VM_UFFD_MISSING) in shmem and use the new VM_FAULT_UFFD_MINOR there instead. For configurations that don't enable CONFIG_USERFAULTFD, VM_FAULT_UFFD_MINOR is set to 0. Suggested-by: David Hildenbrand (Red Hat) Signed-off-by: Mike Rapoport (Microsoft) --- include/linux/mm_types.h | 10 +++++++++- mm/memory.c | 2 ++ mm/shmem.c | 2 +- 3 files changed, 12 insertions(+), 2 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 90e5790c318f..df71b057111b 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1523,6 +1523,8 @@ typedef __bitwise unsigned int vm_fault_t; * fsync() to complete (for synchronous page faults * in DAX) * @VM_FAULT_COMPLETED: ->fault completed, meanwhile mmap lock released + * @VM_FAULT_UFFD_MINOR: ->fault did not modify page tables and needs + * handle_userfault(VM_UFFD_MINOR) to complete * @VM_FAULT_HINDEX_MASK: mask HINDEX value * */ @@ -1540,6 +1542,11 @@ enum vm_fault_reason { VM_FAULT_DONE_COW = (__force vm_fault_t)0x001000, VM_FAULT_NEEDDSYNC = (__force vm_fault_t)0x002000, VM_FAULT_COMPLETED = (__force vm_fault_t)0x004000, +#ifdef CONFIG_USERFAULTFD + VM_FAULT_UFFD_MINOR = (__force vm_fault_t)0x008000, +#else + VM_FAULT_UFFD_MINOR = (__force vm_fault_t)0x000000, +#endif VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000, }; @@ -1564,7 +1571,8 @@ enum vm_fault_reason { { VM_FAULT_FALLBACK, "FALLBACK" }, \ { VM_FAULT_DONE_COW, "DONE_COW" }, \ { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }, \ - { VM_FAULT_COMPLETED, "COMPLETED" } + { VM_FAULT_COMPLETED, "COMPLETED" }, \ + { VM_FAULT_UFFD_MINOR, "UFFD_MINOR" }, \ struct vm_special_mapping { const char *name; /* The name, e.g. "[vdso]". */ diff --git a/mm/memory.c b/mm/memory.c index b59ae7ce42eb..94acbac8cefb 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5279,6 +5279,8 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) } ret = vma->vm_ops->fault(vmf); + if (unlikely(ret & VM_FAULT_UFFD_MINOR)) + return handle_userfault(vmf, VM_UFFD_MINOR); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | VM_FAULT_DONE_COW))) return ret; diff --git a/mm/shmem.c b/mm/shmem.c index e16c7c8c3e1e..a9a31c0b5979 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2461,7 +2461,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, if (folio && vma && userfaultfd_minor(vma)) { if (!xa_is_value(folio)) folio_put(folio); - *fault_type = handle_userfault(vmf, VM_UFFD_MINOR); + *fault_type = VM_FAULT_UFFD_MINOR; return 0; } -- 2.50.1