Re: [PATCH] uio: Replace mutex info_lock with percpu_ref to improve performance

From: kernel test robot
Date: Tue Feb 08 2022 - 08:29:58 EST

Hi Guixin,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on v5.17-rc3 next-20220208]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/0day-ci/linux/commits/Guixin-Liu/uio-Replace-mutex-info_lock-with-percpu_ref-to-improve-performance/20220208-152119
base: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git b86f32951d173b43d1db8de883473fc53dc3c772
config: parisc-randconfig-s032-20220208 (https://download.01.org/0day-ci/archive/20220208/202202082111.R18zUEHK-lkp@xxxxxxxxx/config)
compiler: hppa-linux-gcc (GCC) 11.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/271c7d04f21a7c880e9dfb056eca51835576833d
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Guixin-Liu/uio-Replace-mutex-info_lock-with-percpu_ref-to-improve-performance/20220208-152119
git checkout 271c7d04f21a7c880e9dfb056eca51835576833d
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=parisc SHELL=/bin/bash drivers/uio/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>


sparse warnings: (new ones prefixed by >>)
>> drivers/uio/uio.c:564:24: sparse: sparse: incorrect type in return expression (different base types) @@ expected restricted __poll_t @@ got int @@
drivers/uio/uio.c:564:24: sparse: expected restricted __poll_t
drivers/uio/uio.c:564:24: sparse: got int
drivers/uio/uio.c:567:21: sparse: sparse: incorrect type in assignment (different base types) @@ expected restricted __poll_t [usertype] ret @@ got int @@
drivers/uio/uio.c:567:21: sparse: expected restricted __poll_t [usertype] ret
drivers/uio/uio.c:567:21: sparse: got int
>> drivers/uio/uio.c:699:24: sparse: sparse: incorrect type in return expression (different base types) @@ expected restricted vm_fault_t @@ got int @@
drivers/uio/uio.c:699:24: sparse: expected restricted vm_fault_t
drivers/uio/uio.c:699:24: sparse: got int

vim +564 drivers/uio/uio.c

556
557 static __poll_t uio_poll(struct file *filep, poll_table *wait)
558 {
559 struct uio_listener *listener = filep->private_data;
560 struct uio_device *idev = listener->dev;
561 __poll_t ret = 0;
562
563 if (!percpu_ref_tryget_live(&idev->info_ref))
> 564 return -EINVAL;
565
566 if (!idev->info || !idev->info->irq)
567 ret = -EIO;
568 percpu_ref_put(&idev->info_ref);
569
570 if (ret)
571 return ret;
572
573 poll_wait(filep, &idev->wait, wait);
574 if (listener->event_count != atomic_read(&idev->event))
575 return EPOLLIN | EPOLLRDNORM;
576 return 0;
577 }
578
579 static ssize_t uio_read(struct file *filep, char __user *buf,
580 size_t count, loff_t *ppos)
581 {
582 struct uio_listener *listener = filep->private_data;
583 struct uio_device *idev = listener->dev;
584 DECLARE_WAITQUEUE(wait, current);
585 ssize_t retval = 0;
586 s32 event_count;
587
588 if (count != sizeof(s32))
589 return -EINVAL;
590
591 add_wait_queue(&idev->wait, &wait);
592
593 do {
594 if (!percpu_ref_tryget_live(&idev->info_ref)) {
595 retval = -EINVAL;
596 break;
597 }
598
599 if (!idev->info || !idev->info->irq) {
600 retval = -EIO;
601 percpu_ref_put(&idev->info_ref);
602 break;
603 }
604 percpu_ref_put(&idev->info_ref);
605
606 set_current_state(TASK_INTERRUPTIBLE);
607
608 event_count = atomic_read(&idev->event);
609 if (event_count != listener->event_count) {
610 __set_current_state(TASK_RUNNING);
611 if (copy_to_user(buf, &event_count, count))
612 retval = -EFAULT;
613 else {
614 listener->event_count = event_count;
615 retval = count;
616 }
617 break;
618 }
619
620 if (filep->f_flags & O_NONBLOCK) {
621 retval = -EAGAIN;
622 break;
623 }
624
625 if (signal_pending(current)) {
626 retval = -ERESTARTSYS;
627 break;
628 }
629 schedule();
630 } while (1);
631
632 __set_current_state(TASK_RUNNING);
633 remove_wait_queue(&idev->wait, &wait);
634
635 return retval;
636 }
637
638 static ssize_t uio_write(struct file *filep, const char __user *buf,
639 size_t count, loff_t *ppos)
640 {
641 struct uio_listener *listener = filep->private_data;
642 struct uio_device *idev = listener->dev;
643 ssize_t retval;
644 s32 irq_on;
645
646 if (count != sizeof(s32))
647 return -EINVAL;
648
649 if (copy_from_user(&irq_on, buf, count))
650 return -EFAULT;
651
652 if (!percpu_ref_tryget_live(&idev->info_ref))
653 return -EINVAL;
654
655 if (!idev->info) {
656 retval = -EINVAL;
657 goto out;
658 }
659
660 if (!idev->info->irq) {
661 retval = -EIO;
662 goto out;
663 }
664
665 if (!idev->info->irqcontrol) {
666 retval = -ENOSYS;
667 goto out;
668 }
669
670 retval = idev->info->irqcontrol(idev->info, irq_on);
671
672 out:
673 percpu_ref_put(&idev->info_ref);
674 return retval ? retval : sizeof(s32);
675 }
676
677 static int uio_find_mem_index(struct vm_area_struct *vma)
678 {
679 struct uio_device *idev = vma->vm_private_data;
680
681 if (vma->vm_pgoff < MAX_UIO_MAPS) {
682 if (idev->info->mem[vma->vm_pgoff].size == 0)
683 return -1;
684 return (int)vma->vm_pgoff;
685 }
686 return -1;
687 }
688
689 static vm_fault_t uio_vma_fault(struct vm_fault *vmf)
690 {
691 struct uio_device *idev = vmf->vma->vm_private_data;
692 struct page *page;
693 unsigned long offset;
694 void *addr;
695 vm_fault_t ret = 0;
696 int mi;
697
698 if (!percpu_ref_tryget_live(&idev->info_ref))
> 699 return -EINVAL;
700
701 if (!idev->info) {
702 ret = VM_FAULT_SIGBUS;
703 goto out;
704 }
705
706 mi = uio_find_mem_index(vmf->vma);
707 if (mi < 0) {
708 ret = VM_FAULT_SIGBUS;
709 goto out;
710 }
711
712 /*
713 * We need to subtract mi because userspace uses offset = N*PAGE_SIZE
714 * to use mem[N].
715 */
716 offset = (vmf->pgoff - mi) << PAGE_SHIFT;
717
718 addr = (void *)(unsigned long)idev->info->mem[mi].addr + offset;
719 if (idev->info->mem[mi].memtype == UIO_MEM_LOGICAL)
720 page = virt_to_page(addr);
721 else
722 page = vmalloc_to_page(addr);
723 get_page(page);
724 vmf->page = page;
725
726 out:
727 percpu_ref_put(&idev->info_ref);
728 return ret;
729 }
730

---
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