Re: [Qemu-devel] [V2 06/25] [virtio-9p] coroutines for readlink

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, May 18, 2011 at 7:42 PM, Venkateswararao Jujjuri
<jvrao@linux.vnet.ibm.com> wrote:
> On 05/18/2011 02:43 AM, Stefan Hajnoczi wrote:
>>
>> On Tue, May 17, 2011 at 8:43 PM, Venkateswararao Jujjuri (JV)
>> <jvrao@linux.vnet.ibm.com>  wrote:
>>>
>>> Signed-off-by: Venkateswararao Jujjuri "<jvrao@linux.vnet.ibm.com>
>>> ---
>>>  Makefile.objs            |    2 +-
>>>  hw/9pfs/cofs.c           |   42
>>> ++++++++++++++++++++++++++++++++++++++++++
>>>  hw/9pfs/virtio-9p-coth.h |    1 +
>>>  hw/9pfs/virtio-9p.c      |   27 ++++-----------------------
>>>  hw/9pfs/virtio-9p.h      |    3 ++-
>>>  5 files changed, 50 insertions(+), 25 deletions(-)
>>>  create mode 100644 hw/9pfs/cofs.c
>>>
>>> diff --git a/Makefile.objs b/Makefile.objs
>>> index 96f6a24..36005bb 100644
>>> --- a/Makefile.objs
>>> +++ b/Makefile.objs
>>> @@ -297,7 +297,7 @@ hw-obj-$(CONFIG_SOUND) += $(sound-obj-y)
>>>  9pfs-nested-$(CONFIG_VIRTFS) = virtio-9p.o virtio-9p-debug.o
>>>  9pfs-nested-$(CONFIG_VIRTFS) +=  virtio-9p-local.o virtio-9p-xattr.o
>>>  9pfs-nested-$(CONFIG_VIRTFS) +=   virtio-9p-xattr-user.o
>>> virtio-9p-posix-acl.o
>>> -9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-coth.o
>>> +9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-coth.o cofs.o
>>>
>>>  hw-obj-$(CONFIG_REALLY_VIRTFS) += $(addprefix 9pfs/, $(9pfs-nested-y))
>>>  $(addprefix 9pfs/, $(9pfs-nested-y)): QEMU_CFLAGS+=$(GLIB_CFLAGS)
>>> diff --git a/hw/9pfs/cofs.c b/hw/9pfs/cofs.c
>>> new file mode 100644
>>> index 0000000..6d94673
>>> --- /dev/null
>>> +++ b/hw/9pfs/cofs.c
>>> @@ -0,0 +1,42 @@
>>> +
>>> +/*
>>> + * Virtio 9p backend
>>> + *
>>> + * Copyright IBM, Corp. 2011
>>> + *
>>> + * Authors:
>>> + *  Aneesh Kumar K.V<aneesh.kumar@linux.vnet.ibm.com>
>>> + *
>>> + * This work is licensed under the terms of the GNU GPL, version 2.  See
>>> + * the COPYING file in the top-level directory.
>>> + *
>>> + */
>>> +
>>> +#include "fsdev/qemu-fsdev.h"
>>> +#include "qemu-thread.h"
>>> +#include "qemu-coroutine.h"
>>> +#include "virtio-9p-coth.h"
>>> +
>>> +int v9fs_co_readlink(V9fsState *s, V9fsString *path, V9fsString *buf)
>>> +{
>>> +    int err;
>>> +    ssize_t len;
>>> +    V9fsString tbuf;
>>> +
>>> +    tbuf.data = qemu_malloc(PATH_MAX);
>>
>> Why introduce tbuf when the buf is available?  You end up having to
>> copy back fields at the end of the function and load from an
>> uninitialized address (tbuf.size) in the error case.
>
> tbuf is introduced for re-entrent purpose.
> We should be calling v9fs_string_init() on this though.

I see no issue here and no safety added by using a local variable.
Can you explain what you're trying to do?

Stefan