Re: running out of tags in 9P (was Re: [git pull] vfs part 2)

From	Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups	linux.kernel
Subject	Re: running out of tags in 9P (was Re: [git pull] vfs part 2)
Date	2015-07-02 10:30 +0200
Message-ID	<pHI2C-gz-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <pHDmj-5MZ-9@gated-at.bofh.it> <pHE8G-6jo-3@gated-at.bofh.it> <pHHzA-8iF-17@gated-at.bofh.it> <pHHzA-8iF-15@gated-at.bofh.it> <pHHSW-cZ-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Thu, Jul 02, 2015 at 11:19:03AM +0300, Andrey Ryabinin wrote:
> Besides qemu, I've also tried kvmtool with the same result. IOW I'm seeing
> this under kvmtool as well. It just takes a bit longer to reproduce
> this in kvmtool.
> 
> > The bug I suspected to be the cause of that is in tag allocation in
> > net/9p/client.c - we could end up wrapping around 2^16 with enough pending
> > requests and that would have triggered that kind of mess.  However, Andrey
> > doesn't see that test (tag wraparound in p9_client_prepare_req()) trigger.
> > BTW, was that on the run where debugging printk in p9_client_write() *did*
> > trigger?
> 
> Yes, WARN_ON_ONCE() in p9_client_prepare_req() didn't trigger,
> but debug printk in p9_client_write() *did* trigger.

Bloody wonderful...  Could you check if v9fs_write() in qemu
hw/9pfs/virtio-9p.c ever gets to
    offset = 7;
    err = pdu_marshal(pdu, offset, "d", total);
with total > count on your testcase?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Thread

Re: [git pull] vfs part 2 Andrey Ryabinin <a.ryabinin@samsung.com> - 2015-07-01 10:00 +0200
  Re: [git pull] vfs part 2 Al Viro <viro@ZenIV.linux.org.uk> - 2015-07-01 10:30 +0200
    Re: [git pull] vfs part 2 Andrey Ryabinin <a.ryabinin@samsung.com> - 2015-07-01 10:50 +0200
      Re: [git pull] vfs part 2 Al Viro <viro@ZenIV.linux.org.uk> - 2015-07-01 11:00 +0200
        Re: running out of tags in 9P (was Re: [git pull] vfs part 2) Al Viro <viro@ZenIV.linux.org.uk> - 2015-07-02 10:30 +0200
          Re: running out of tags in 9P (was Re: [git pull] vfs part 2) Al Viro <viro@ZenIV.linux.org.uk> - 2015-07-02 10:50 +0200
            Re: running out of tags in 9P (was Re: [git pull] vfs part 2) Andrey Ryabinin <a.ryabinin@samsung.com> - 2015-07-02 14:30 +0200
              Re: running out of tags in 9P (was Re: [git pull] vfs part 2) Al Viro <viro@ZenIV.linux.org.uk> - 2015-07-03 11:50 +0200
                [PATCH] forgetting to cancel request in interrupted zero-copy 9P RPC  (was Re: [git pull] vfs part 2) Al Viro <viro@ZenIV.linux.org.uk> - 2015-07-03 17:10 +0200

csiph-web