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 X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E05F5C2BABC for ; Sat, 4 Apr 2020 09:41:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B744520739 for ; Sat, 4 Apr 2020 09:41:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="V91+pfIB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726396AbgDDJlb (ORCPT ); Sat, 4 Apr 2020 05:41:31 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:37356 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726387AbgDDJla (ORCPT ); Sat, 4 Apr 2020 05:41:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=AqMtuIfKhyb9qBOeLF2ngCbDbTkgWPlfw5hjLkqb7k0=; b=V91+pfIB+e0EjxYrdGBz6mZLeU b6sl/kba8YztMoKxFixyGrWr2+p6+TfA0D2AjbbjkY2bZIGjyOrkiEGXkydG/usWfjQAgQeph03/p IWY4AL97ClQJOz6TWS+xW7Q5iK9baeejsY4mWXxok+AnXwWf653d3wli0gWSTPPlZ6KaOgRSwSOl5 ZU06lYY6VKTEueQ24UaKOf1HYDEX1xNZgSOexOSURxirYAwMPmyD5kygFhpOgyfR/W1FL0cGLBzUE 0gBw5EZWuSLQPZ/XjtACPARRjtV8sgcPjEmiku93dzKae7Y9qUh6wCDy895raR0m7+CLsUAZ0uQnk j8K7x5+A==; Received: from [2001:4bb8:180:7914:2ca6:9476:bbfa:a4d0] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jKfIo-0002e8-4W; Sat, 04 Apr 2020 09:41:22 +0000 From: Christoph Hellwig To: Linus Torvalds , Andrew Morton Cc: Al Viro , Felix Kuehling , Alex Deucher , Zhenyu Wang , Zhi Wang , Felipe Balbi , "Michael S. Tsirkin" , Jason Wang , Jens Axboe , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-usb@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 6/6] kernel: set USER_DS in kthread_use_mm Date: Sat, 4 Apr 2020 11:41:01 +0200 Message-Id: <20200404094101.672954-7-hch@lst.de> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200404094101.672954-1-hch@lst.de> References: <20200404094101.672954-1-hch@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Some architectures like arm64 and s390 require USER_DS to be set for kernel threads to access user address space, which is the whole purpose of kthread_use_mm, but other like x86 don't. That has lead to a huge mess where some callers are fixed up once they are tested on said architectures, while others linger around and yet other like io_uring try to do "clever" optimizations for what usually is just a trivial asignment to a member in the thread_struct for most architectures. Make kthread_use_mm set USER_DS, and kthread_unuse_mm restore to the previous value instead. Signed-off-by: Christoph Hellwig --- drivers/usb/gadget/function/f_fs.c | 4 ---- drivers/vhost/vhost.c | 3 --- fs/io-wq.c | 8 ++------ fs/io_uring.c | 4 ---- kernel/kthread.c | 6 ++++++ 5 files changed, 8 insertions(+), 17 deletions(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index d9e48bd7c692..a1198f4c527c 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -824,13 +824,9 @@ static void ffs_user_copy_worker(struct work_struct *work) bool kiocb_has_eventfd = io_data->kiocb->ki_flags & IOCB_EVENTFD; if (io_data->read && ret > 0) { - mm_segment_t oldfs = get_fs(); - - set_fs(USER_DS); kthread_use_mm(io_data->mm); ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data); kthread_unuse_mm(io_data->mm); - set_fs(oldfs); } io_data->kiocb->ki_complete(io_data->kiocb, ret, ret); diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 1787d426a956..b5229ae01d3b 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -333,9 +333,7 @@ static int vhost_worker(void *data) struct vhost_dev *dev = data; struct vhost_work *work, *work_next; struct llist_node *node; - mm_segment_t oldfs = get_fs(); - set_fs(USER_DS); kthread_use_mm(dev->mm); for (;;) { @@ -365,7 +363,6 @@ static int vhost_worker(void *data) } } kthread_unuse_mm(dev->mm); - set_fs(oldfs); return 0; } diff --git a/fs/io-wq.c b/fs/io-wq.c index 83c2868eff2a..75cc2f31816d 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -168,7 +168,6 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker) dropped_lock = true; } __set_current_state(TASK_RUNNING); - set_fs(KERNEL_DS); kthread_unuse_mm(worker->mm); mmput(worker->mm); worker->mm = NULL; @@ -420,14 +419,11 @@ static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work) mmput(worker->mm); worker->mm = NULL; } - if (!work->mm) { - set_fs(KERNEL_DS); + if (!work->mm) return; - } + if (mmget_not_zero(work->mm)) { kthread_use_mm(work->mm); - if (!worker->mm) - set_fs(USER_DS); worker->mm = work->mm; /* hang on to this mm */ work->mm = NULL; diff --git a/fs/io_uring.c b/fs/io_uring.c index 367406381044..c332a34e8b34 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5871,15 +5871,12 @@ static int io_sq_thread(void *data) struct io_ring_ctx *ctx = data; struct mm_struct *cur_mm = NULL; const struct cred *old_cred; - mm_segment_t old_fs; DEFINE_WAIT(wait); unsigned long timeout; int ret = 0; complete(&ctx->completions[1]); - old_fs = get_fs(); - set_fs(USER_DS); old_cred = override_creds(ctx->creds); timeout = jiffies + ctx->sq_thread_idle; @@ -5985,7 +5982,6 @@ static int io_sq_thread(void *data) if (current->task_works) task_work_run(); - set_fs(old_fs); if (cur_mm) { kthread_unuse_mm(cur_mm); mmput(cur_mm); diff --git a/kernel/kthread.c b/kernel/kthread.c index 316db17f6b4f..9e27d01b6d78 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -52,6 +52,7 @@ struct kthread { unsigned long flags; unsigned int cpu; void *data; + mm_segment_t oldfs; struct completion parked; struct completion exited; #ifdef CONFIG_BLK_CGROUP @@ -1235,6 +1236,9 @@ void kthread_use_mm(struct mm_struct *mm) if (active_mm != mm) mmdrop(active_mm); + + to_kthread(tsk)->oldfs = get_fs(); + set_fs(USER_DS); } EXPORT_SYMBOL_GPL(kthread_use_mm); @@ -1249,6 +1253,8 @@ void kthread_unuse_mm(struct mm_struct *mm) WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); WARN_ON_ONCE(!tsk->mm); + set_fs(to_kthread(tsk)->oldfs); + task_lock(tsk); sync_mm_rss(mm); tsk->mm = NULL; -- 2.25.1