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 EDE13549371; Thu, 17 Sep 2026 16:32:09 +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=1789662731; cv=none; b=bl6dt7niiuxRtFNKh6SeN1GKGW2sTLdjI+zVkwYYnrIzZnLdwzxBj8teokKCJptSznPIfEN99Qof7RmojFnX6Tk4ESNPKbZrg/MD2eG6JZdmvqOH9Uzj7K7wRxv7A5fKVoXl8/CpG3MhHqbWiClhE+G6BuhOieM/tqFJI/XAu+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789662731; c=relaxed/simple; bh=HTYbod2OP3AjRPEv6Ph886TsUDFUWldGDo6PKBX7Wqs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=h8CRp2L8edqOHE7xYRgGW4rlYp15nUIdCIcbZkEC4tMu4UlBIWqEk0NMhyRUrMTtCp5ylv4TrxMvNjsMLinWkVbvciiHqs6DRdu3bAX4IgHDP5M427PDvfzjDgB/5hbFr7u3PajYtffQ3sw8jMGDm/W0DH8sGzD3t1YCs3ZI1NM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Em9Vcp7v; 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="Em9Vcp7v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F145F1F00898; Thu, 17 Sep 2026 16:31:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789662729; bh=zqpk9MXgaX25nS5Ys5rO6UCVR/iTsHvR4Kg11ITNpTs=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=Em9Vcp7vsIS4Jn8qf/ahkPwaLGTBcJ8S5LIKDJMNWb3KRHsMyPmFX4JPiU7TvPOmF +MrSzGz5nbDpirTrKKpT7f6veK5ZPsJ2sVnniUA2IYHo6fkoPifqJuSw6gsonsSdOk qXJfQMLxAO1xfepbXhdfm+6hYk7pWgyENu3ZHr5AgPibg54dq2nQxPUic4WtiQZx5A DwAUQEVEZXEwEOTOE62x/pD269SFWj0pYwkt33CXVoAPjv7oZfWr5BxshfaNUB250A h9QMdMAmTMKLNhEYJLvTV4VhhkZ0P8xHGGUUAVCdZVEIt0VSeavBiKuRA5nUo2iTbx bVHAAHQknK+jw== From: "Lorenzo Stoakes (ARM)" Date: Thu, 17 Sep 2026 17:22:27 +0100 Subject: [PATCH v3 18/40] scsi: sg: convert mmap hook to mmap_prepare and rework Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-18-4583d8a23bca@kernel.org> References: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> In-Reply-To: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> To: Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , David Hildenbrand , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Greg Kroah-Hartman , Dennis Dalessandro , Jason Gunthorpe , Leon Romanovsky , Paul Moore , Stephen Smalley , Jaroslav Kysela , Takashi Iwai , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" , Jaya Kumar , Simona Vetter , Helge Deller , Sebastian Reichel , John Hubbard , Peter Xu , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Rik van Riel , Harry Yoo , Juri Lelli , Vincent Guittot , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Arnd Bergmann , Muchun Song , Oscar Salvador , "Matthew Wilcox (Oracle)" , Jan Kara , Marc Zyngier , Oliver Upton , Catalin Marinas , Madhavan Srinivasan , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , "David S. Miller" , Andreas Larsson , Alexander Viro , Christian Brauner , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park , Johannes Weiner , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chengming Zhou , Michal Hocko , Miklos Szeredi , Xu Xin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-usb@vger.kernel.org, linux-rdma@vger.kernel.org, selinux@vger.kernel.org, linux-sound@vger.kernel.org, bpf@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, fuse-devel@lists.linux.dev, "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=5937; i=ljs@kernel.org; h=from:subject:message-id; bh=HTYbod2OP3AjRPEv6Ph886TsUDFUWldGDo6PKBX7Wqs=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLLWCB+MTmlykN749ErGgtLIbfJWW1wOmzJePeXSkp6a7 iw7/7ZYRykLgxgXg6yYIsvzL+L7g0TC5nVe8HeDmcPKBDKEgYtTACay7x3D/+Iwtu3lofl/9wnM 1bQpCNefY17DevBw5pv01fefayU83s/wT5t1Z0mEyM2PT4XbeZ4tWbny13uNg/Ymxre/m73J9S3 vZgMA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Move from the deprecated mmap hook to the new mmap_prepare hook. We are mapping kernel pages here, so use the discontiguous kernel mapping mmap action to do so. Unwind the rather confusing loop and instead map as many pages as we can at one time. Note that we do not need to pay attention to rsv_schp->k_use_sg here, as the pages are populated for the length of the buffer at rsv_schp->page_order granularity as compound pages. The discontiguous kernel page mapping logic handles the compound pages for us. sfp->mmap_called keeps the buffer stable for us. As before it is never cleared, so a failed mmap also leaves it set. We also remove some useless vma, vma->vm_file NULL checks - these will always be non-NULL if you reached the mmap hook logic. We retain log output for consistency, but change what's output on page mapping to indicate that sg_discontig_get() does the work now. Note that we drop the VMA_IO_BIT flag for the VMA here. It was never necessary as we invoke alloc_pages() which gives us refcounted folios that are fine for GUP to access (VMA_IO_BIT would prevent that). Signed-off-by: Lorenzo Stoakes (ARM) --- drivers/scsi/sg.c | 115 ++++++++++++++++++++++++------------------------------ 1 file changed, 51 insertions(+), 64 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 5408f002e6c0..3f9e08725602 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1212,85 +1212,72 @@ sg_fasync(int fd, struct file *filp, int mode) return fasync_helper(fd, filp, mode, &sfp->async_qp); } -static vm_fault_t -sg_vma_fault(struct vm_fault *vmf) +static int sg_discontig_init(void *vm_private_data, void **private) { - struct vm_area_struct *vma = vmf->vma; - Sg_fd *sfp; - unsigned long offset, len, sa; - Sg_scatter_hold *rsv_schp; - int k, length; - - if ((NULL == vma) || (!(sfp = (Sg_fd *) vma->vm_private_data))) - return VM_FAULT_SIGBUS; - rsv_schp = &sfp->reserve; - offset = vmf->pgoff << PAGE_SHIFT; - if (offset >= rsv_schp->bufflen) - return VM_FAULT_SIGBUS; - SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sfp->parentdp, - "sg_vma_fault: offset=%lu, scatg=%d\n", - offset, rsv_schp->k_use_sg)); - sa = vma->vm_start; - length = 1 << (PAGE_SHIFT + rsv_schp->page_order); - for (k = 0; k < rsv_schp->k_use_sg && sa < vma->vm_end; k++) { - len = vma->vm_end - sa; - len = (len < length) ? len : length; - if (offset < len) { - struct page *page = rsv_schp->pages[k] + (offset >> PAGE_SHIFT); - get_page(page); /* increment page count */ - vmf->page = page; - return 0; /* success */ - } - sa += len; - offset -= len; + const unsigned long req_sz = (unsigned long)*private; + Sg_fd *sfp = vm_private_data; + Sg_scatter_hold *rsv_schp = &sfp->reserve; + int err = 0; + + mutex_lock(&sfp->f_mutex); + if (req_sz > rsv_schp->bufflen) { + err = -ENOMEM; /* cannot map more than reserved buffer */ + goto out; + } + sfp->mmap_called = 1; /* Prevents changes to buffer size. */ +out: + mutex_unlock(&sfp->f_mutex); + return err; +} + +static int +sg_discontig_get(struct discontig_kernel_page_state *state) +{ + Sg_fd *sfp = state->vm_private_data; + Sg_scatter_hold *rsv_schp = &sfp->reserve; + const unsigned int order = rsv_schp->page_order; + const pgoff_t nr_pages = state->nr_pages_mapped; + + if (nr_pages >= (rsv_schp->bufflen >> PAGE_SHIFT)) { + discontig_kernel_map_abort(state); + return 0; } - return VM_FAULT_SIGBUS; + SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sfp->parentdp, + "%s: offset=%lu, scatg=%d\n", __func__, + nr_pages << PAGE_SHIFT, rsv_schp->k_use_sg)); + + discontig_kernel_map_page(state, rsv_schp->pages[nr_pages >> order]); + return 0; } -static const struct vm_operations_struct sg_mmap_vm_ops = { - .fault = sg_vma_fault, +static const struct discontig_kernel_page_ops sg_discontig_ops = { + .init = sg_discontig_init, + .get = sg_discontig_get, }; static int -sg_mmap(struct file *filp, struct vm_area_struct *vma) +sg_mmap_prepare(struct vm_area_desc *desc) { - Sg_fd *sfp; - unsigned long req_sz, len, sa; - Sg_scatter_hold *rsv_schp; - int k, length; - int ret = 0; + Sg_fd *sfp = desc->file->private_data; + const unsigned long req_sz = vma_desc_size(desc); - if ((!filp) || (!vma) || (!(sfp = (Sg_fd *) filp->private_data))) + if (!sfp) return -ENXIO; - req_sz = vma->vm_end - vma->vm_start; + SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sfp->parentdp, "sg_mmap starting, vm_start=%p, len=%d\n", - (void *) vma->vm_start, (int) req_sz)); - if (vma->vm_pgoff) + (void *) desc->start, (int) req_sz)); + + if (desc->pgoff) return -EINVAL; /* want no offset */ - rsv_schp = &sfp->reserve; - mutex_lock(&sfp->f_mutex); - if (req_sz > rsv_schp->bufflen) { - ret = -ENOMEM; /* cannot map more than reserved buffer */ - goto out; - } - sa = vma->vm_start; - length = 1 << (PAGE_SHIFT + rsv_schp->page_order); - for (k = 0; k < rsv_schp->k_use_sg && sa < vma->vm_end; k++) { - len = vma->vm_end - sa; - len = (len < length) ? len : length; - sa += len; - } + vma_desc_set_flags(desc, VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT); + desc->private_data = sfp; - sfp->mmap_called = 1; - vm_flags_set(vma, VM_IO | VM_DONTEXPAND | VM_DONTDUMP); - vma->vm_private_data = sfp; - vma->vm_ops = &sg_mmap_vm_ops; -out: - mutex_unlock(&sfp->f_mutex); - return ret; + mmap_action_map_discontig_kernel_pages(desc, (void *)req_sz, + &sg_discontig_ops); + return 0; } static void @@ -1415,7 +1402,7 @@ static const struct file_operations sg_fops = { .unlocked_ioctl = sg_ioctl, .compat_ioctl = compat_ptr_ioctl, .open = sg_open, - .mmap = sg_mmap, + .mmap_prepare = sg_mmap_prepare, .release = sg_release, .fasync = sg_fasync, }; -- 2.55.0