| Message ID | 20200404094101.672954-7-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/6] amdgpu: a NULL ->mm does not mean a thread is a kthread | expand |
On Sat, Apr 04, 2020 at 11:41:01AM +0200, Christoph Hellwig wrote: > 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 <hch@lst.de> I'm ok with vhost bits: Acked-by: Michael S. Tsirkin <mst@redhat.com> > --- > 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
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;
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 <hch@lst.de> --- 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(-)