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 26A77D116F6 for ; Sun, 30 Nov 2025 11:18:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 823576B0011; Sun, 30 Nov 2025 06:18:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7ACA06B0012; Sun, 30 Nov 2025 06:18:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 64E1F6B0022; Sun, 30 Nov 2025 06:18:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 4FE356B0011 for ; Sun, 30 Nov 2025 06:18:41 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id E58C3132541 for ; Sun, 30 Nov 2025 11:18:40 +0000 (UTC) X-FDA: 84167025600.29.1B03EEA Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf26.hostedemail.com (Postfix) with ESMTP id 3577614000F for ; Sun, 30 Nov 2025 11:18:39 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=GTEOZ3Eu; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf26.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764501519; a=rsa-sha256; cv=none; b=BBczRQyaIJpBiLQHA0Grg9Y1yb0Xl0T8OYKB1T3SJq8D3K2aKRzAiiAQeM0nOwmbWSrphq bC7CTe5BiOTtpHvqB/rdRi0QRqMO2V+UxzzM7IBQTxAAsPKAyunWUuW2nX3PCB37S54jVo noZANV5E9uaAEhWXe+vmL+IxzEIKYlo= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=GTEOZ3Eu; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf26.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 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=1764501519; 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=luA8w64UTnP7jsE/Fp6ukORsax4OgFVbVD1J93HbfUs=; b=lUIiBU8m652DIdg+v6aY6bMotCCR4PuE8HDSL/v54Q0YIoAdtyX5mKdD9DcOA5Sj8AH/TB 4CoWXm0jUCnQtrbsnZm7Hzyt9y7OtRVT7iUlN32bvmT85ja4133XiDVMa3HZNV8edm3kTu NaY7vAQx1OEOiHAueqU3oBhG45nDelM= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 6B99442E17; Sun, 30 Nov 2025 11:18:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07FF8C4CEF8; Sun, 30 Nov 2025 11:18:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764501518; bh=kn1TtLxUvl6eK2HP+wAu3G67BEAmX/GRyBo9yQ844/o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GTEOZ3Eu7EhOOpw0QceVSQ+bNm50XMZUIp8tcd4Zgvs0pWvWMI60KTlM1/2qOsjs8 0QNc7mcCdeh+ZYHJdpxS3KVSQ/SnooeWvfX+xjVwFwOh4Ayxh+9nNH2/z4SVTQ2tru XyufTc0QVGWP4mrQ1s+rWBm3P5+VvAxusEBYIHg43KX0tY4wWgDncOlh2ocwiBSqYe Gj8ZzBLL92wwmYW1GSIbx7rQtkZp+Ed1rAhaF7XuAsqylo7q5xqWa9fqzLfpNrRXho f84MYsqTzz/pbvZL+4dlHYdlYCUFxPVyZXIS9nNk422W47CGVnoXf9AyAZRUfhrIhP +UKoQejLcsRGg== 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 v3 3/5] mm: introduce VM_FAULT_UFFD_MINOR fault reason Date: Sun, 30 Nov 2025 13:18:10 +0200 Message-ID: <20251130111812.699259-4-rppt@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251130111812.699259-1-rppt@kernel.org> References: <20251130111812.699259-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3577614000F X-Stat-Signature: z36me7c6tseej8ysswah66o5cjowac6d X-Rspam-User: X-HE-Tag: 1764501519-536308 X-HE-Meta: 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 nLoWxY+F 26L7lLHUDV3nfW7SLYeGNMZNIpeCkZqwmaenCDmvW25Ta5RLQdtcvoMve5ccmTXSroD9TCu7toqdz3t2pudpQoeRm9MB0KnPF7SweNNvA6jYTfx0DaCE1WC0MgGabEq+MjUULXrAuBGsSRWAfrob41eSwfBPIkDC6K6Sbaw35OhE9eGJjnJNA1dXEZtfe42bPvBSMLhJd3DOhY4+V1h+3m98E1C/hj7zkDYowZLcRfHtlYbG883OYWCFRbwT5G3Py9+6X71JB7uEfXvnBMma7/Av45v78IDMHDdf9WAJgNGUoLxUXNLlktqHsXk8DSXoaGxTX 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_MINOR). 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_MINOR) to complete a page fault. Replace a call to handle_userfault(VM_UFFD_MINOR) 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 | 5 ++++- mm/shmem.c | 2 +- 3 files changed, 14 insertions(+), 3 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 90e5790c318f..c92a52c572c3 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..8d2180ec6933 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5280,8 +5280,11 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) ret = vma->vm_ops->fault(vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | - VM_FAULT_DONE_COW))) + VM_FAULT_DONE_COW | VM_FAULT_UFFD_MINOR))) { + if (ret & VM_FAULT_UFFD_MINOR) + return handle_userfault(vmf, VM_UFFD_MINOR); return ret; + } folio = page_folio(vmf->page); if (unlikely(PageHWPoison(vmf->page))) { diff --git a/mm/shmem.c b/mm/shmem.c index 9f8c54ad0e32..2c32e2398e99 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2460,7 +2460,7 @@ 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; } -- 2.51.0