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Re: [PATCH v1 3/7] xen: xenstore: add possibility to preserve owner
- To: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
- From: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Date: Mon, 13 Nov 2023 13:02:22 +0000
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- Cc: "qemu-devel@xxxxxxxxxx" <qemu-devel@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Marcel Apfelbaum <marcel.apfelbaum@xxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Richard Henderson <richard.henderson@xxxxxxxxxx>, Eduardo Habkost <eduardo@xxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony Perard <anthony.perard@xxxxxxxxxx>, "open list:X86 Xen CPUs" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 13 Nov 2023 13:02:46 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHaFBZoS99E/RofVU6d/7dbafCRirB09L6AgAI+uwCAAQc9AA==
- Thread-topic: [PATCH v1 3/7] xen: xenstore: add possibility to preserve owner
Hi David,
David Woodhouse <dwmw2@xxxxxxxxxxxxx> writes:
> [[S/MIME Signed Part:Undecided]]
> On Sat, 2023-11-11 at 11:01 +0000, David Woodhouse wrote:
>>
>> > --- a/hw/xen/xen-operations.c
>> > +++ b/hw/xen/xen-operations.c
>> > @@ -300,6 +300,18 @@ static bool libxenstore_create(struct qemu_xs_handle
>> > *h, xs_transaction_t t,
>> > return false;
>> > }
>> >
>> > + if (owner == XS_PRESERVE_OWNER) {
>> > + struct xs_permissions *tmp;
>> > + unsigned int num;
>> > +
>> > + tmp = xs_get_permissions(h->xsh, 0, path, &num);
>> > + if (tmp == NULL) {
>> > + return false;
>> > + }
>> > + perms_list[0].id = tmp[0].id;
>> > + free(tmp);
>> > + }
>> > +
>>
>> Don't see what saves you from someone else changing it at this point on
>> true Xen though. Which is why I'd prefer XenStore to do it natively.
>
> I suppose maybe you could do it in a transaction *if* the transaction_t
> you're passed in isn't already XBT_NULL?
Yes, I need to pass "t" to xs_get_permissions(), of course.
> One might argue that the mkdir+set_perms in libxenstore_create() ought
> to have been within the same transaction *anyway*?
Yes, all operations should be performed inside one transaction.
--
WBR, Volodymyr
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