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 6300AC2D0EF for ; Thu, 16 Apr 2020 05:32:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1A32C20771 for ; Thu, 16 Apr 2020 05:32:16 +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="NW+cnTIK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1A32C20771 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 69F3B8E007E; Thu, 16 Apr 2020 01:32:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4E5E88E0080; 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 310C38E0001; Thu, 16 Apr 2020 01:32:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0180.hostedemail.com [216.40.44.180]) by kanga.kvack.org (Postfix) with ESMTP id 109168E007E for ; Thu, 16 Apr 2020 01:32:15 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id BED9C5DFD for ; Thu, 16 Apr 2020 05:32:14 +0000 (UTC) X-FDA: 76712597388.11.shake36_1383adb82075c X-HE-Tag: shake36_1383adb82075c X-Filterd-Recvd-Size: 12931 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Thu, 16 Apr 2020 05:32:13 +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=hjp14iUZlRKTsu3uiFZgsg/rZSgDThHclQfpO/jd+7A=; b=NW+cnTIKfLE8yZDKQxf0Vg0THe 5H5KzRETI5QOYIlFyPmeCgPjtkaUhqXHeZZZGR/B+w8PXjfEd3lNa9Mj4/QGOn9tRUvEyT/HP9ZIp cKEl09X0/SbpZcRbE1Mh7Vb8zgGIkzoVR64uw8oNvPmVn2QsTvA69pwSJU2Q9bz6jt8JwGUEha4a3 nEyjxcyILK4jFRfqVPEF9h3TFLMWpf06HDpQ10he4+pJSYC72xrIKSlVdJSFZ2mOVmnJ/zSW+Wkkg up4NceVeglq0unxoki79IiA560yjgT195Q5ZMkbfrmRVZHPrxLQzMKmwpSM4G7LUPJzX6NE+e8U3J 03vtijDA==; 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 1jOx89-0003dI-PY; Thu, 16 Apr 2020 05:32:06 +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 2/3] kernel: better document the use_mm/unuse_mm API contract Date: Thu, 16 Apr 2020 07:31:57 +0200 Message-Id: <20200416053158.586887-3-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: Switch the function documentation to kerneldoc comments, and add WARN_ON_ONCE asserts that the calling thread is a kernel thread and does not have ->mm set (or has ->mm set in the case of unuse_mm). Also give the functions a kthread_ prefix to better document the use case. Signed-off-by: Christoph Hellwig Acked-by: Felix Kuehling --- drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h | 4 +-- drivers/gpu/drm/i915/gvt/kvmgt.c | 4 +-- drivers/usb/gadget/function/f_fs.c | 4 +-- drivers/usb/gadget/legacy/inode.c | 4 +-- drivers/vfio/vfio_iommu_type1.c | 4 +-- drivers/vhost/vhost.c | 4 +-- fs/io-wq.c | 6 ++-- fs/io_uring.c | 6 ++-- include/linux/kthread.h | 4 +-- kernel/kthread.c | 33 +++++++++++----------- mm/oom_kill.c | 6 ++-- mm/vmacache.c | 4 +-- 12 files changed, 41 insertions(+), 42 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h b/drivers/gpu/drm= /amd/amdgpu/amdgpu_amdkfd.h index b820c8fc689f..b063bd7f41d8 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h @@ -192,9 +192,9 @@ uint8_t amdgpu_amdkfd_get_xgmi_hops_count(struct kgd_= dev *dst, struct kgd_dev *s if ((mmptr) =3D=3D current->mm) { \ valid =3D !get_user((dst), (wptr)); \ } else if (current->mm =3D=3D NULL) { \ - use_mm(mmptr); \ + kthread_use_mm(mmptr); \ valid =3D !get_user((dst), (wptr)); \ - unuse_mm(mmptr); \ + kthread_unuse_mm(mmptr); \ } \ pagefault_enable(); \ } \ diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/= kvmgt.c index ca1dd6e6f395..f2927575b793 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -2048,7 +2048,7 @@ static int kvmgt_rw_gpa(unsigned long handle, unsig= ned long gpa, if (kthread) { if (!mmget_not_zero(kvm->mm)) return -EFAULT; - use_mm(kvm->mm); + kthread_use_mm(kvm->mm); } =20 idx =3D srcu_read_lock(&kvm->srcu); @@ -2057,7 +2057,7 @@ static int kvmgt_rw_gpa(unsigned long handle, unsig= ned long gpa, srcu_read_unlock(&kvm->srcu, idx); =20 if (kthread) { - unuse_mm(kvm->mm); + kthread_unuse_mm(kvm->mm); mmput(kvm->mm); } =20 diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/func= tion/f_fs.c index c57b1b2507c6..d9e48bd7c692 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -827,9 +827,9 @@ static void ffs_user_copy_worker(struct work_struct *= work) mm_segment_t oldfs =3D get_fs(); =20 set_fs(USER_DS); - use_mm(io_data->mm); + kthread_use_mm(io_data->mm); ret =3D ffs_copy_to_iter(io_data->buf, ret, &io_data->data); - unuse_mm(io_data->mm); + kthread_unuse_mm(io_data->mm); set_fs(oldfs); } =20 diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legac= y/inode.c index 8b5233888bf8..a05552bc2ff8 100644 --- a/drivers/usb/gadget/legacy/inode.c +++ b/drivers/usb/gadget/legacy/inode.c @@ -462,9 +462,9 @@ static void ep_user_copy_worker(struct work_struct *w= ork) struct kiocb *iocb =3D priv->iocb; size_t ret; =20 - use_mm(mm); + kthread_use_mm(mm); ret =3D copy_to_iter(priv->buf, priv->actual, &priv->to); - unuse_mm(mm); + kthread_unuse_mm(mm); if (!ret) ret =3D -EFAULT; =20 diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_ty= pe1.c index 5f50866a8b01..2eb105aa9723 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -2333,7 +2333,7 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfi= o_iommu *iommu, return -EPERM; =20 if (kthread) - use_mm(mm); + kthread_use_mm(mm); else if (current->mm !=3D mm) goto out; =20 @@ -2351,7 +2351,7 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfi= o_iommu *iommu, *copied =3D __copy_from_user(data, (void __user *)vaddr, count) ? 0 : count; if (kthread) - unuse_mm(mm); + kthread_unuse_mm(mm); out: mmput(mm); return *copied ? 0 : -EFAULT; diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index ead1deed80d3..17d598e74780 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -332,7 +332,7 @@ static int vhost_worker(void *data) mm_segment_t oldfs =3D get_fs(); =20 set_fs(USER_DS); - use_mm(dev->mm); + kthread_use_mm(dev->mm); =20 for (;;) { /* mb paired w/ kthread_stop */ @@ -360,7 +360,7 @@ static int vhost_worker(void *data) schedule(); } } - unuse_mm(dev->mm); + kthread_unuse_mm(dev->mm); set_fs(oldfs); return 0; } diff --git a/fs/io-wq.c b/fs/io-wq.c index 5f590bf27bff..748621f7391e 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -170,7 +170,7 @@ static bool __io_worker_unuse(struct io_wqe *wqe, str= uct io_worker *worker) } __set_current_state(TASK_RUNNING); set_fs(KERNEL_DS); - unuse_mm(worker->mm); + kthread_unuse_mm(worker->mm); mmput(worker->mm); worker->mm =3D NULL; } @@ -417,7 +417,7 @@ static struct io_wq_work *io_get_next_work(struct io_= wqe *wqe) static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work = *work) { if (worker->mm) { - unuse_mm(worker->mm); + kthread_unuse_mm(worker->mm); mmput(worker->mm); worker->mm =3D NULL; } @@ -426,7 +426,7 @@ static void io_wq_switch_mm(struct io_worker *worker,= struct io_wq_work *work) return; } if (mmget_not_zero(work->mm)) { - use_mm(work->mm); + kthread_use_mm(work->mm); if (!worker->mm) set_fs(USER_DS); worker->mm =3D work->mm; diff --git a/fs/io_uring.c b/fs/io_uring.c index f5a80f6f28f5..8a8148512da7 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5876,7 +5876,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, = unsigned int nr, err =3D -EFAULT; goto fail_req; } - use_mm(ctx->sqo_mm); + kthread_use_mm(ctx->sqo_mm); *mm =3D ctx->sqo_mm; } =20 @@ -5948,7 +5948,7 @@ static int io_sq_thread(void *data) * may sleep. */ if (cur_mm) { - unuse_mm(cur_mm); + kthread_unuse_mm(cur_mm); mmput(cur_mm); cur_mm =3D NULL; } @@ -6025,7 +6025,7 @@ static int io_sq_thread(void *data) =20 set_fs(old_fs); if (cur_mm) { - unuse_mm(cur_mm); + kthread_unuse_mm(cur_mm); mmput(cur_mm); } revert_creds(old_cred); diff --git a/include/linux/kthread.h b/include/linux/kthread.h index c2d40c9672d6..12258ea077cf 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -200,8 +200,8 @@ bool kthread_cancel_delayed_work_sync(struct kthread_= delayed_work *work); =20 void kthread_destroy_worker(struct kthread_worker *worker); =20 -void use_mm(struct mm_struct *mm); -void unuse_mm(struct mm_struct *mm); +void kthread_use_mm(struct mm_struct *mm); +void kthread_unuse_mm(struct mm_struct *mm); =20 struct cgroup_subsys_state; =20 diff --git a/kernel/kthread.c b/kernel/kthread.c index ce4610316377..8ed4b4fbec7c 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -1208,18 +1208,18 @@ void kthread_destroy_worker(struct kthread_worker= *worker) } EXPORT_SYMBOL(kthread_destroy_worker); =20 -/* - * use_mm - * Makes the calling kernel thread take on the specified - * mm context. - * (Note: this routine is intended to be called only - * from a kernel thread context) +/** + * kthread_use_mm - make the calling kthread operate on an address space + * @mm: address space to operate on */ -void use_mm(struct mm_struct *mm) +void kthread_use_mm(struct mm_struct *mm) { struct mm_struct *active_mm; struct task_struct *tsk =3D current; =20 + WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); + WARN_ON_ONCE(tsk->mm); + task_lock(tsk); active_mm =3D tsk->active_mm; if (active_mm !=3D mm) { @@ -1236,20 +1236,19 @@ void use_mm(struct mm_struct *mm) if (active_mm !=3D mm) mmdrop(active_mm); } -EXPORT_SYMBOL_GPL(use_mm); +EXPORT_SYMBOL_GPL(kthread_use_mm); =20 -/* - * unuse_mm - * Reverses the effect of use_mm, i.e. releases the - * specified mm context which was earlier taken on - * by the calling kernel thread - * (Note: this routine is intended to be called only - * from a kernel thread context) +/** + * kthread_unuse_mm - reverse the effect of kthread_use_mm() + * @mm: address space to operate on */ -void unuse_mm(struct mm_struct *mm) +void kthread_unuse_mm(struct mm_struct *mm) { struct task_struct *tsk =3D current; =20 + WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); + WARN_ON_ONCE(!tsk->mm); + task_lock(tsk); sync_mm_rss(mm); tsk->mm =3D NULL; @@ -1257,7 +1256,7 @@ void unuse_mm(struct mm_struct *mm) enter_lazy_tlb(mm, tsk); task_unlock(tsk); } -EXPORT_SYMBOL_GPL(unuse_mm); +EXPORT_SYMBOL_GPL(kthread_unuse_mm); =20 #ifdef CONFIG_BLK_CGROUP /** diff --git a/mm/oom_kill.c b/mm/oom_kill.c index dfc357614e56..958d2972313f 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -126,7 +126,7 @@ static bool oom_cpuset_eligible(struct task_struct *t= sk, struct oom_control *oc) =20 /* * The process p may have detached its own ->mm while exiting or through - * use_mm(), but one or more of its subthreads may still have a valid + * kthread_use_mm(), but one or more of its subthreads may still have a = valid * pointer. Return p, or any of its subthreads with a valid ->mm, with * task_lock() held. */ @@ -919,8 +919,8 @@ static void __oom_kill_process(struct task_struct *vi= ctim, const char *message) continue; } /* - * No use_mm() user needs to read from the userspace so we are - * ok to reap it. + * No kthead_use_mm() user needs to read from the userspace so + * we are ok to reap it. */ if (unlikely(p->flags & PF_KTHREAD)) continue; diff --git a/mm/vmacache.c b/mm/vmacache.c index cdc32a3b02fa..ceedbab82106 100644 --- a/mm/vmacache.c +++ b/mm/vmacache.c @@ -25,8 +25,8 @@ * task's vmacache pertains to a different mm (ie, its own). There is * nothing we can do here. * - * Also handle the case where a kernel thread has adopted this mm via us= e_mm(). - * That kernel thread's vmacache is not applicable to this mm. + * Also handle the case where a kernel thread has adopted this mm via + * kthread_use_mm(). That kernel thread's vmacache is not applicable to = this mm. */ static inline bool vmacache_valid_mm(struct mm_struct *mm) { --=20 2.25.1