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 B4512D2FEDB for ; Tue, 27 Jan 2026 19:31:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EA2E16B00A7; Tue, 27 Jan 2026 14:31:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E77E66B00A9; Tue, 27 Jan 2026 14:31:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D97546B00AA; Tue, 27 Jan 2026 14:31:05 -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 C526E6B00A7 for ; Tue, 27 Jan 2026 14:31:05 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 8BD48C18A1 for ; Tue, 27 Jan 2026 19:31:05 +0000 (UTC) X-FDA: 84378736890.29.2D0DF9F Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf19.hostedemail.com (Postfix) with ESMTP id F10A01A0011 for ; Tue, 27 Jan 2026 19:31:03 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=q2UsiRPu; spf=pass (imf19.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1769542264; 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=LNQNFWvrb8GbRlkZV4SG+Lijf3yLWl1JfogTIgexFRY=; b=6G/L2QG3+Qu9j3eJYjsHbrw8mFx5Cea/l6VZXhydjDqKwvHMXMr4hio3fBKoM6UQfjlSlU 7IL8CDJOp84Tq+GsUe5Xep9nVCNfvD2raf1j3lzCNhBUb6zb3srlitxgmpJDieJbMFgMgL JwNLt1KNt0xmMQqM7625qCi/+cNSulc= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=q2UsiRPu; spf=pass (imf19.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1769542264; a=rsa-sha256; cv=none; b=3phmYTFBhMm8EEdJ5BNnaoXIWHxn+f78XPnnYFSjsYBF/m7JCMyouVTO1YxfG4uu6Nol4R rtVAxI2IpttLzopIk19778ugBXnQXgBmpPf9ph0ypR0sPCM5p4PoIrQcS7mEick8RAYDBA aQgn4YSby0uTdD1EBrd3+te5tsWaDTU= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 4DB2160202; Tue, 27 Jan 2026 19:31:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F19B2C116C6; Tue, 27 Jan 2026 19:30:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769542262; bh=h+TcgWCVPD30aK45h+wpUIJypZftXhAg5ucXDIazF9Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q2UsiRPuaj/8L0lU3PZimX+KdU+NnUJ4T6kgHnK7oKJ7dnF20S1Wu60dtz3r+KU1H 0T+7qAEjj3JbVgEGy3R0Hx3DRfjX2B6I9PzRs1e6vap8/WGmkswqz84raN0EuooQAV 5E4A1pVzNprdPWdgwAmWXAr69bCVgPHlBxziKewff7xctTxCeA2TMO1wQzD8XqEI6f Ed4jSaIIhYNV6/OJpzSKzJ1lZMwUBOT5T1blV/qYiHyC03fgIpcZ1vmjVxxtXEnaon 0hSCYpfGeJVTvH9YpHOBZSgxib2aLHu9IQ7ZrqCo73Rgfq3eGnPiCbchrIFCt6eypg 1wteWBH/FqJkQ== 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 , Muchun Song , Nikita Kalyazin , Oscar Salvador , 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 RFC 12/17] mm: introduce VM_FAULT_UFFD_MINOR fault reason Date: Tue, 27 Jan 2026 21:29:31 +0200 Message-ID: <20260127192936.1250096-13-rppt@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260127192936.1250096-1-rppt@kernel.org> References: <20260127192936.1250096-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 9zw8ceykiu6iby6owhc1i4mfdpjad9fp X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: F10A01A0011 X-HE-Tag: 1769542263-255873 X-HE-Meta: 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 xrLSMNRc 6ICWGcVgDXfI73SVRz479BEA314I40HjP1j0H3MV72LeS069p7zP9mriC6alFf27WlEYZGU1FC58E8j81mgBr0bFPrcF3PSxuhWZ31Qd673B8a/EWel46seHACtV+hKPpLGlBY+FzYvywJSShkdN7MvlSDBIrstooNXU6UH1yHwpUbqP26GmTqK8236Cs1n5DRUHzNEIXPASwwPciqz//jVO8CXFWglm+iw/M64RMvZ8eI4NCfsyYQSyiF9M6A6fiVvFcFQ2RlNFnrnfsclXADWS7fIvyuVlxlQWdtu3NwxrsSAkmhjXvJrIGv1LpzOLrWfwgnBSnbzEeyMl2pxcXsovedw== 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: Nikita Kalyazin 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 42af2292951d..b25ac322bfbf 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1555,6 +1555,8 @@ 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 * */ @@ -1572,6 +1574,11 @@ 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, }; @@ -1596,7 +1603,8 @@ 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 2a55edc48a65..fcb3e0c3113e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5319,8 +5319,11 @@ 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 6f0485f76cb8..6aa905147c0c 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2481,7 +2481,7 @@ 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