From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 85457383323 for ; Thu, 21 May 2026 16:22:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779380526; cv=none; b=fdmYSLqbrVicbuzoSowcN3KGaQHPwEzoL3O1L7u/wh/gRjpj1M+HC1DrSzM929rnlOLIduGtIufJnun4ea8xuswhu+uyNkoFVfR8lAcCmAn/2zTgsjsGzxUwZmpzAS/3mo0qbu9LUzqsE0adqDXpxXHUpmWOvx+wbRr6SHWufvY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779380526; c=relaxed/simple; bh=WK0l9+vzVVCbYlX7zepos3VbftKtGp22qSUGWAJi0Pw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Db9I3GJwyi43k3sfc8yzh1bhRgeKFZiaLOkaubqrvcUciaVx3AxaMkYhNAxMDzSPpesmm49i8XBE3EwpRAcqiRLRL5c17q3fN/CflEMKZJm5N1AfId9aJQimLTd1hDhbWz08+wVJhagc+qBYw7dy4kpCymYpP39I2eLM3Tj9rP8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nqjZAVh3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nqjZAVh3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B27081F000E9; Thu, 21 May 2026 16:22:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779380525; bh=dcfNGGjgx+NSZAuu90jBs3Qr8P55dHAXd7ftObLSo1w=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nqjZAVh3PyIoAeEkzPIV1rUZ6koUPIajoobZVez4REJMBrP5PUMiCT4NA+vjfKxzC 5VXS/ogr8g8x8JzO1bGf6z3gEI4LpMM6VQMB7WzQRDK2EheYvrUDs9KSP51FxqiGw7 KcjFZl6X+Tl2CHi9HHx0JMxuXTej35em5oq4Xm9SZRwtg2eJ0Y7gCY0buuxkjbWhg5 7eoPyLV/T1+hQJEwZErnyU9Qyo+fbXbrbTLjRAPD9R3mNV7nul71qXBUj+lqnTg4Qt MzwY+EqvemEENsHd3SueAxjspmnc0uzm4mtOyY6NBla/uvDuoYKOYRrYgPEGo3DXnX uvq30KXMIO8yw== From: Lorenzo Stoakes To: Andrew Morton Cc: Arnd Bergmann , Greg Kroah-Hartman , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 1/3] drivers/char/mem: eliminate unnecessary use of success_hook Date: Thu, 21 May 2026 17:21:52 +0100 Message-ID: <68bd08d2c7432f94b87f9e40f379336860a9997c.1779379804.git.ljs@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce vma_desc_set_anonymous() and invoke it from mmap_zero_prepare() in order to eliminate the use of the mmap_action->success_hook. Note that file-backed VMAs default to vma->vm_ops == dummy_vm_ops, so if an mmap or mmap_prepare hook does not set desc->vm_ops, the VMA will remain file-backed. We also update set_vma_user_defined_fields() to make clear that we are either setting vma->vm_ops to what is provided by the driver (or defaulting to dummy_vm_ops if not set), or setting the VMA anonymous. This lays the groundwork for removing the success hook, which was provided as a workaround for drivers (mostly, hugetlb) that still absolutely seemed to rely upon having access to a VMA pointer. However, for the transition to be useful, we really must eliminate this and make no exceptions, otherwise drivers can simply work around it. Signed-off-by: Lorenzo Stoakes --- drivers/char/mem.c | 17 +++++------------ include/linux/mm.h | 5 +++++ mm/vma.c | 2 ++ 3 files changed, 12 insertions(+), 12 deletions(-) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 5fd421e48c04..a4297eb39887 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -504,17 +504,6 @@ static ssize_t read_zero(struct file *file, char __user *buf, return cleared; } -static int mmap_zero_private_success(const struct vm_area_struct *vma) -{ - /* - * This is a highly unique situation where we mark a MAP_PRIVATE mapping - * of /dev/zero anonymous, despite it not being. - */ - vma_set_anonymous((struct vm_area_struct *)vma); - - return 0; -} - static int mmap_zero_prepare(struct vm_area_desc *desc) { #ifndef CONFIG_MMU @@ -523,7 +512,11 @@ static int mmap_zero_prepare(struct vm_area_desc *desc) if (vma_desc_test(desc, VMA_SHARED_BIT)) return shmem_zero_setup_desc(desc); - desc->action.success_hook = mmap_zero_private_success; + /* + * This is a highly unique situation where we mark a MAP_PRIVATE mapping + * of /dev/zero anonymous, despite it not being. + */ + vma_desc_set_anonymous(desc); return 0; } diff --git a/include/linux/mm.h b/include/linux/mm.h index 9cedc5e75aa9..2138c86403f5 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1489,6 +1489,11 @@ static inline void vma_set_anonymous(struct vm_area_struct *vma) vma->vm_ops = NULL; } +static inline void vma_desc_set_anonymous(struct vm_area_desc *desc) +{ + desc->vm_ops = NULL; +} + static inline bool vma_is_anonymous(struct vm_area_struct *vma) { return !vma->vm_ops; diff --git a/mm/vma.c b/mm/vma.c index d90791b00a7b..07486390c692 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2697,6 +2697,8 @@ static void set_vma_user_defined_fields(struct vm_area_struct *vma, { if (map->vm_ops) vma->vm_ops = map->vm_ops; + else /* Only /dev/zero should do this. */ + vma_set_anonymous(vma); vma->vm_private_data = map->vm_private_data; } -- 2.54.0