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Re: [Qemu-devel] [PATCH v2] usb-mtp: Add fallback definition of NAME_MAX
From: |
Kamil Rytarowski |
Subject: |
Re: [Qemu-devel] [PATCH v2] usb-mtp: Add fallback definition of NAME_MAX |
Date: |
Tue, 5 Sep 2017 01:22:53 +0200 |
User-agent: |
Mozilla/5.0 (X11; NetBSD amd64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
On 04.09.2017 19:50, Peter Maydell wrote:
> On 4 September 2017 at 18:25, Kamil Rytarowski <address@hidden> wrote:
>> This fixes build on SmartOS (Joyent).
>>
>> Patch cherry-picked from pkgsrc by jperkin (Joyent).
>>
>> Signed-off-by: Kamil Rytarowski <address@hidden>
>> Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
>> ---
>> include/qemu/osdep.h | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
>> index 6855b94bbf..5d3860f80e 100644
>> --- a/include/qemu/osdep.h
>> +++ b/include/qemu/osdep.h
>> @@ -306,6 +306,11 @@ void qemu_anon_ram_free(void *ptr, size_t size);
>> #endif
>> #endif
>>
>> +/* Required by SmartOS (SunOS) */
>> +#ifndef NAME_MAX
>> +#define NAME_MAX 255
>> +#endif
>
> So in hw/usb/dev-mtp.c we're using NAME_MAX in
> char buf[sizeof(struct inotify_event) + NAME_MAX + 1];
>
> because the Linux implementation of inotify documents in inotify(7)
> that this is guaranteed to be sufficient to read at least one event:
> http://man7.org/linux/man-pages/man7/inotify.7.html
> Looking at the SmartOS manpage
> https://smartos.org/man/5/inotify
> there doesn't seem to be any equivalent language.
>
> What is the SmartOS requirement on the buffer size to be
> guaranteed to read at least one complete event ?
> Defining NAME_MAX to 255 seems like it shuts up the compiler
> error but does it give us the correct behaviour?
>
According to my understanding SmartOS has the same logic. It tries to
read at least one element, and NAME_MAX guarantees that it will be
available.
https://github.com/joyent/illumos-joyent/blob/master/usr/src/uts/common/io/inotify.c#L1193
I've gathered some overall details about the patches.
1. The inotify linux-compat interface is only SmartOS specific, it
hasn't been upstreamed so far to other Illumos distributions.
2. Upstream Illumos implemented NAME_MAX
https://github.com/illumos/illumos-gate/commit/9c0752ac0dc05794d2f8a8b4521d55e2b3f63247
It's not available in SmartOS.
3. Proprietary Solaris is out of scope of this work.
Looking at their userland we can assume no qemu support:
https://github.com/oracle/solaris-userland
https://github.com/oracle/solaris-userland/commit/9c78c7b45a5d3dbd64afb455d278d2ca277e2b95#diff-94df904ebca88ee0ff038eaedb063ad6R61
++ if platform.system() == 'SunOS':
++ # No QEMU support on Solaris now.
++ qemu_img = False
We can stop pretending to support it now.
4. SmartOS forked qemu for its hypervisor part and uses qemu-kvm with
the Linux kvm interface (yes, there is Linux kernel kvm port to SmartOS)
- upstreaming the hypervisor's fork is out of scope.
https://github.com/joyent/illumos-kvm-cmd
5. SmartOS ships with virtual machine guests, they host pkgsrc and qemu
from pkgsrc.
6. Jonathan mentioned that preparing a SmartOS tutorial and image will
be tricky, as SmartOS is a hypervisor. I will focus on upstreaming
SmartOS-guest support for qemu, where there is pkgsrc. There is an
option to prepare another Illumos distribution tutorial and testbot,
hopefully it will be fully compatible with SmartOS patches.
> thanks
> -- PMM
>
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