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=-9.5 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 11014C3A5A0 for ; Thu, 16 Apr 2020 05:32:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B110120784 for ; Thu, 16 Apr 2020 05:32:19 +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="YibKIVsw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B110120784 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9EF858E0080; Thu, 16 Apr 2020 01:32:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9A10A8E0001; Thu, 16 Apr 2020 01:32:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 88D8D8E0081; Thu, 16 Apr 2020 01:32:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0221.hostedemail.com [216.40.44.221]) by kanga.kvack.org (Postfix) with ESMTP id 659018E0001 for ; Thu, 16 Apr 2020 01:32:15 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 284F18245578 for ; Thu, 16 Apr 2020 05:32:15 +0000 (UTC) X-FDA: 76712597430.23.glove49_1397a2994c63a X-HE-Tag: glove49_1397a2994c63a X-Filterd-Recvd-Size: 6910 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Thu, 16 Apr 2020 05:32:14 +0000 (UTC) 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=067wQeP/XsQZz7g9kDshfnJ5VToeesdhipVsn0gNrtY=; b=YibKIVswQ5pUBnsRMM6VfjsvQ8 g4PkIfoEwbBcSGD1mLF+cQGk90fOYWm0fTmHuUNjn6GTpQXyIWjV4KoR08kg9crGiaO89xCJvC/0j tyOiapEMb0oHb8sAiYMe6l55EZ2juDaT/0ZiN7o50JEV4RaKsxdjS1w5hhsuNy4H3Ua1KZ+QsQ76i h9udkToejdlmgZPNEn3mYobJY6O79O2dzot1xmq7C1Asm8KAZ9OyZGJMK2joYCbz7VGjYLzEzOGc1 jqkNWWfMFa/3SegvAOVFQRy65e82bVNzbrubo/KsI2n28M9QW1nzS6EMiyZ0NApYCYFDbesPY5sci iWGGTEsg==; Received: from [2001:4bb8:184:4aa1:c70:4a89:bc61:2] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOx8C-0003dn-CA; Thu, 16 Apr 2020 05:32:08 +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 3/3] kernel: set USER_DS in kthread_use_mm Date: Thu, 16 Apr 2020 07:31:58 +0200 Message-Id: <20200416053158.586887-4-hch@lst.de> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200416053158.586887-1-hch@lst.de> References: <20200416053158.586887-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Content-Transfer-Encoding: quoted-printable 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: 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 Acked-by: Michael S. Tsirkin [vhost] --- 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/func= tion/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 =3D io_data->kiocb->ki_flags & IOCB_EVENTFD; =20 if (io_data->read && ret > 0) { - mm_segment_t oldfs =3D get_fs(); - - set_fs(USER_DS); kthread_use_mm(io_data->mm); ret =3D ffs_copy_to_iter(io_data->buf, ret, &io_data->data); kthread_unuse_mm(io_data->mm); - set_fs(oldfs); } =20 io_data->kiocb->ki_complete(io_data->kiocb, ret, ret); diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 17d598e74780..b2abfbdf3cb2 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -329,9 +329,7 @@ static int vhost_worker(void *data) struct vhost_dev *dev =3D data; struct vhost_work *work, *work_next; struct llist_node *node; - mm_segment_t oldfs =3D get_fs(); =20 - set_fs(USER_DS); kthread_use_mm(dev->mm); =20 for (;;) { @@ -361,7 +359,6 @@ static int vhost_worker(void *data) } } kthread_unuse_mm(dev->mm); - set_fs(oldfs); return 0; } =20 diff --git a/fs/io-wq.c b/fs/io-wq.c index 748621f7391e..a5e90ac39e4d 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -169,7 +169,6 @@ static bool __io_worker_unuse(struct io_wqe *wqe, str= uct io_worker *worker) dropped_lock =3D true; } __set_current_state(TASK_RUNNING); - set_fs(KERNEL_DS); kthread_unuse_mm(worker->mm); mmput(worker->mm); worker->mm =3D NULL; @@ -421,14 +420,11 @@ static void io_wq_switch_mm(struct io_worker *worke= r, struct io_wq_work *work) mmput(worker->mm); worker->mm =3D 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 =3D work->mm; /* hang on to this mm */ work->mm =3D NULL; diff --git a/fs/io_uring.c b/fs/io_uring.c index 8a8148512da7..40f90b98a18a 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5908,15 +5908,12 @@ static int io_sq_thread(void *data) struct io_ring_ctx *ctx =3D data; struct mm_struct *cur_mm =3D NULL; const struct cred *old_cred; - mm_segment_t old_fs; DEFINE_WAIT(wait); unsigned long timeout; int ret =3D 0; =20 complete(&ctx->completions[1]); =20 - old_fs =3D get_fs(); - set_fs(USER_DS); old_cred =3D override_creds(ctx->creds); =20 timeout =3D jiffies + ctx->sq_thread_idle; @@ -6023,7 +6020,6 @@ static int io_sq_thread(void *data) if (current->task_works) task_work_run(); =20 - 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 8ed4b4fbec7c..86357cd38eb2 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) =20 if (active_mm !=3D mm) mmdrop(active_mm); + + to_kthread(tsk)->oldfs =3D get_fs(); + set_fs(USER_DS); } EXPORT_SYMBOL_GPL(kthread_use_mm); =20 @@ -1249,6 +1253,8 @@ void kthread_unuse_mm(struct mm_struct *mm) WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); WARN_ON_ONCE(!tsk->mm); =20 + set_fs(to_kthread(tsk)->oldfs); + task_lock(tsk); sync_mm_rss(mm); tsk->mm =3D NULL; --=20 2.25.1