From nobody Thu Sep 19 23:56:01 2024 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A53BBC636D3 for ; Fri, 3 Feb 2023 03:02:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232424AbjBCDCc (ORCPT ); Thu, 2 Feb 2023 22:02:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232182AbjBCDCL (ORCPT ); Thu, 2 Feb 2023 22:02:11 -0500 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C78083929E; Thu, 2 Feb 2023 19:01:52 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045192;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0Vamlo-T_1675393309; Received: from localhost(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0Vamlo-T_1675393309) by smtp.aliyun-inc.com; Fri, 03 Feb 2023 11:01:50 +0800 From: Jingbo Xu To: xiang@kernel.org, chao@kernel.org, linux-erofs@lists.ozlabs.org Cc: huyue2@coolpad.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v3 7/9] erofs: implement .mmap for page cache sharing Date: Fri, 3 Feb 2023 11:01:41 +0800 Message-Id: <20230203030143.73105-8-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20230203030143.73105-1-jefflexu@linux.alibaba.com> References: <20230203030143.73105-1-jefflexu@linux.alibaba.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" In mmap(2), replace vma->vm_file with the anonymous file associated with the blob, so that the vma will be linked to the address_space of the blob. One thing worth noting is that, we return error early in mmap(2) if users attempt to map beyond the file size. Normally filesystems won't restrict this in mmap(2). The checking is done in the fault handler, and SIGBUS will be signaled to users if they actually attempt to access the area beyond the end of the file. However since vma->vm_file has been changed to the anonymous file in mmap(2), we can no way derive the file size of the original file. As file size is immutable in ro filesystem, let's fail early in mmap(2) in this case. Signed-off-by: Jingbo Xu --- fs/erofs/fscache.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c index bdeb048b78b5..af6ba52bbe8b 100644 --- a/fs/erofs/fscache.c +++ b/fs/erofs/fscache.c @@ -432,9 +432,36 @@ static ssize_t erofs_fscache_share_file_read_iter(stru= ct kiocb *iocb, return res; } =20 +vm_fault_t erofs_fscache_share_fault(struct vm_fault *vmf) +{ + struct erofs_fscache_finfo *finfo =3D vmf->vma->vm_file->private_data; + + if (unlikely(vmf->pgoff >=3D finfo->max_idx)) + return VM_FAULT_SIGBUS; + return filemap_fault(vmf); +} + +static const struct vm_operations_struct erofs_fscache_share_file_vm_ops = =3D { + .fault =3D erofs_fscache_share_fault, +}; + +static int erofs_fscache_share_file_mmap(struct file *file, + struct vm_area_struct *vma) +{ + struct file *realfile =3D file->private_data; + struct erofs_fscache_finfo *finfo =3D realfile->private_data; + + vma_set_file(vma, realfile); + vma->vm_pgoff =3D (finfo->pa >> PAGE_SHIFT) + vma->vm_pgoff; + vma->vm_ops =3D &erofs_fscache_share_file_vm_ops; + file_accessed(file); + return 0; +} + const struct file_operations erofs_fscache_share_file_fops =3D { .llseek =3D generic_file_llseek, .read_iter =3D erofs_fscache_share_file_read_iter, + .mmap =3D erofs_fscache_share_file_mmap, .open =3D erofs_fscache_share_file_open, .release =3D erofs_fscache_share_file_release, }; --=20 2.19.1.6.gb485710b