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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 5/6] kernel: better document the use_mm/unuse_mm API contract Date: Sat, 4 Apr 2020 11:41:00 +0200 Message-Id: <20200404094101.672954-6-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 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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/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 +-- 11 files changed, 39 insertions(+), 40 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h index bce5e93fefc8..63db84e09408 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) == current->mm) { \ valid = !get_user((dst), (wptr)); \ } else if (current->flags & PF_KTHREAD) { \ - use_mm(mmptr); \ + kthread_use_mm(mmptr); \ valid = !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 dee01c371bf5..92e9b340dbc2 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, unsigned long gpa, if (kthread) { if (!mmget_not_zero(kvm->mm)) return -EFAULT; - use_mm(kvm->mm); + kthread_use_mm(kvm->mm); } idx = srcu_read_lock(&kvm->srcu); @@ -2057,7 +2057,7 @@ static int kvmgt_rw_gpa(unsigned long handle, unsigned long gpa, srcu_read_unlock(&kvm->srcu, idx); if (kthread) { - unuse_mm(kvm->mm); + kthread_unuse_mm(kvm->mm); mmput(kvm->mm); } diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/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 = get_fs(); set_fs(USER_DS); - use_mm(io_data->mm); + kthread_use_mm(io_data->mm); ret = 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); } diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/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 *work) struct kiocb *iocb = priv->iocb; size_t ret; - use_mm(mm); + kthread_use_mm(mm); ret = copy_to_iter(priv->buf, priv->actual, &priv->to); - unuse_mm(mm); + kthread_unuse_mm(mm); if (!ret) ret = -EFAULT; diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 4e9ce54869af..1787d426a956 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -336,7 +336,7 @@ static int vhost_worker(void *data) mm_segment_t oldfs = get_fs(); set_fs(USER_DS); - use_mm(dev->mm); + kthread_use_mm(dev->mm); for (;;) { /* mb paired w/ kthread_stop */ @@ -364,7 +364,7 @@ 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 c49c2bdbafb5..83c2868eff2a 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -169,7 +169,7 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct 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 = NULL; } @@ -416,7 +416,7 @@ 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 = NULL; } @@ -425,7 +425,7 @@ 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 = work->mm; diff --git a/fs/io_uring.c b/fs/io_uring.c index 27a4ecb724ca..367406381044 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5839,7 +5839,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, err = -EFAULT; goto fail_req; } - use_mm(ctx->sqo_mm); + kthread_use_mm(ctx->sqo_mm); *mm = ctx->sqo_mm; } @@ -5911,7 +5911,7 @@ 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 = NULL; } @@ -5987,7 +5987,7 @@ static int io_sq_thread(void *data) 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); void kthread_destroy_worker(struct kthread_worker *worker); -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); struct cgroup_subsys_state; diff --git a/kernel/kthread.c b/kernel/kthread.c index ce4610316377..316db17f6b4f 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); -/* - * 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 = current; + WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); + WARN_ON_ONCE(tsk->mm); + task_lock(tsk); active_mm = tsk->active_mm; if (active_mm != mm) { @@ -1236,20 +1236,19 @@ void use_mm(struct mm_struct *mm) if (active_mm != mm) mmdrop(active_mm); } -EXPORT_SYMBOL_GPL(use_mm); +EXPORT_SYMBOL_GPL(kthread_use_mm); -/* - * 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_use_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 = current; + WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); + WARN_ON_ONCE(!tsk->mm); + task_lock(tsk); sync_mm_rss(mm); tsk->mm = 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); #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 *tsk, struct oom_control *oc) /* * 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 *victim, 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 use_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) {