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Message-Id: <20180930092954.GA4062@rapoport-lnx>
Date: Sun, 30 Sep 2018 12:29:55 +0300
From: Mike Rapoport <rppt@...ux.vnet.ibm.com>
To: Peter Xu <peterx@...hat.com>
Cc: linux-kernel@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Jerome Glisse <jglisse@...hat.com>, linux-mm@...ck.org,
Zi Yan <zi.yan@...rutgers.edu>,
"Kirill A . Shutemov" <kirill@...temov.name>,
linux-kselftest@...r.kernel.org, Shaohua Li <shli@...com>,
Andrea Arcangeli <aarcange@...hat.com>,
"Dr . David Alan Gilbert" <dgilbert@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 2/3] userfaultfd: selftest: generalize read and poll
On Sun, Sep 30, 2018 at 03:42:58PM +0800, Peter Xu wrote:
> We do very similar things in read and poll modes, but we're copying the
> codes around. Share the codes properly on reading the message and
> handling the page fault to make the code cleaner. Meanwhile this solves
> previous mismatch of behaviors between the two modes on that the old
> code:
>
> - did not check EAGAIN case in read() mode
> - ignored BOUNCE_VERIFY check in read() mode
>
> Signed-off-by: Peter Xu <peterx@...hat.com>
Acked-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
> ---
> tools/testing/selftests/vm/userfaultfd.c | 77 +++++++++++++-----------
> 1 file changed, 43 insertions(+), 34 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 5ff3a4f9173e..7a8c6937cc67 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -451,6 +451,43 @@ static int copy_page(int ufd, unsigned long offset)
> return __copy_page(ufd, offset, false);
> }
>
> +static int uffd_read_msg(int ufd, struct uffd_msg *msg)
> +{
> + int ret = read(uffd, msg, sizeof(*msg));
> +
> + if (ret != sizeof(*msg)) {
> + if (ret < 0) {
> + if (errno == EAGAIN)
> + return 1;
> + else
> + perror("blocking read error"), exit(1);
> + } else {
> + fprintf(stderr, "short read\n"), exit(1);
> + }
> + }
> +
> + return 0;
> +}
> +
> +/* Return 1 if page fault handled by us; otherwise 0 */
> +static int uffd_handle_page_fault(struct uffd_msg *msg)
> +{
> + unsigned long offset;
> +
> + if (msg->event != UFFD_EVENT_PAGEFAULT)
> + fprintf(stderr, "unexpected msg event %u\n",
> + msg->event), exit(1);
> +
> + if (bounces & BOUNCE_VERIFY &&
> + msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
> + fprintf(stderr, "unexpected write fault\n"), exit(1);
> +
> + offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst;
> + offset &= ~(page_size-1);
> +
> + return copy_page(uffd, offset);
> +}
> +
> static void *uffd_poll_thread(void *arg)
> {
> unsigned long cpu = (unsigned long) arg;
> @@ -458,7 +495,6 @@ static void *uffd_poll_thread(void *arg)
> struct uffd_msg msg;
> struct uffdio_register uffd_reg;
> int ret;
> - unsigned long offset;
> char tmp_chr;
> unsigned long userfaults = 0;
>
> @@ -482,25 +518,15 @@ static void *uffd_poll_thread(void *arg)
> if (!(pollfd[0].revents & POLLIN))
> fprintf(stderr, "pollfd[0].revents %d\n",
> pollfd[0].revents), exit(1);
> - ret = read(uffd, &msg, sizeof(msg));
> - if (ret < 0) {
> - if (errno == EAGAIN)
> - continue;
> - perror("nonblocking read error"), exit(1);
> - }
> + if (uffd_read_msg(uffd, &msg))
> + continue;
> switch (msg.event) {
> default:
> fprintf(stderr, "unexpected msg event %u\n",
> msg.event), exit(1);
> break;
> case UFFD_EVENT_PAGEFAULT:
> - if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
> - fprintf(stderr, "unexpected write fault\n"), exit(1);
> - offset = (char *)(unsigned long)msg.arg.pagefault.address -
> - area_dst;
> - offset &= ~(page_size-1);
> - if (copy_page(uffd, offset))
> - userfaults++;
> + userfaults += uffd_handle_page_fault(&msg);
> break;
> case UFFD_EVENT_FORK:
> close(uffd);
> @@ -528,8 +554,6 @@ static void *uffd_read_thread(void *arg)
> {
> unsigned long *this_cpu_userfaults;
> struct uffd_msg msg;
> - unsigned long offset;
> - int ret;
>
> this_cpu_userfaults = (unsigned long *) arg;
> *this_cpu_userfaults = 0;
> @@ -538,24 +562,9 @@ static void *uffd_read_thread(void *arg)
> /* from here cancellation is ok */
>
> for (;;) {
> - ret = read(uffd, &msg, sizeof(msg));
> - if (ret != sizeof(msg)) {
> - if (ret < 0)
> - perror("blocking read error"), exit(1);
> - else
> - fprintf(stderr, "short read\n"), exit(1);
> - }
> - if (msg.event != UFFD_EVENT_PAGEFAULT)
> - fprintf(stderr, "unexpected msg event %u\n",
> - msg.event), exit(1);
> - if (bounces & BOUNCE_VERIFY &&
> - msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
> - fprintf(stderr, "unexpected write fault\n"), exit(1);
> - offset = (char *)(unsigned long)msg.arg.pagefault.address -
> - area_dst;
> - offset &= ~(page_size-1);
> - if (copy_page(uffd, offset))
> - (*this_cpu_userfaults)++;
> + if (uffd_read_msg(uffd, &msg))
> + continue;
> + (*this_cpu_userfaults) += uffd_handle_page_fault(&msg);
> }
> return (void *)NULL;
> }
> --
> 2.17.1
>
--
Sincerely yours,
Mike.
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