Re: [Qemu-devel] Bug in virtio-9p when fstatting an fd referring to a file that no longer exists

[Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>]

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On 04/28/2011 09:51 AM, Sassan Panahinejad wrote:
> This thread seems relevant: 
> http://www.mail-archive.com/linux-fsdevel@vger.kernel.org/msg09159.html
> Unless things have changed, it looks like the problem is in the client 
> kernel (although note that there isn't support in qemu, even if the 
> client did send an fid associated with an open file!).
> Any thoughts on a workaround for this?

Hrm, I don't see any workaround for this. May be we should add TFSTAT 
for dotl? or add a flag to
TSTAT?

Copying the v9fs.

Thanks,
JV


>
>
> Thanks
> Sassan
>
> On 28 April 2011 17:13, Sassan Panahinejad <sassan@sassan.me.uk 
> <mailto:sassan@sassan.me.uk>> wrote:
>
>     It should be possible for guest applications to fstat a file for
>     which they have a valid file descriptor, even if the file has been
>     removed.
>     Demonstrated by the code sample below (fstat reports no such file
>     or directory).
>     Strangely it seems that reading from a file in this state works
>     fine (and when both are run, the server receives a different fid
>     for each).
>     On any other filesystem, the code runs correctly. On our 9p
>     filesystem it fails.
>     Many applications (including bash) depend on this working correctly.
>     I will continue investigating, but any thoughts anyone has on the
>     subject would be appreciated.
>
>
>     Thanks
>     Sassan
>
>
>     #include <stdio.h>
>     #include <unistd.h>
>     #include <fcntl.h>
>     #include <sys/types.h>
>     #include <sys/stat.h>
>
>
>     int main(void)
>     {
>             int ret;
>             struct stat statbuf;
>             int fd = open("test.txt", O_RDWR | O_CREAT, 0666);
>             if (fd < 0) {
>                     printf("open failed: %m\n");
>                     return 1;
>             }
>             ret = write(fd, "test1\n", 6);
>             if (ret < 0) {
>                     printf("write1 failed: %m\n");
>                     return 1;
>             }
>             ret = unlink("test.txt");
>             if (ret < 0) {
>                     printf("unlink failed: %m\n");
>                     return 1;
>             }
>             ret = fstat(fd, &statbuf);
>             if (ret < 0) {
>                     printf("fstat failed: %m\n");
>                     return 1;
>             }
>             return 0;
>     }
>
>


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