On Wed, 2010年04月14日 at 16:12 -0400, Daniel Stodden wrote:
> On Wed, 2010年04月14日 at 12:30 -0400, John McCullough wrote:
> > On 04/14/2010 01:24 AM, Daniel Stodden wrote:
> > > On Wed, 2010年04月14日 at 01:40 -0400, John McCullough wrote:
> > > 
> > >> Daniel,
> > >>
> > >> That did the trick and got us up to 256, Thanks!
> > >>
> > >> Out of curiosity, what's standing in the way of more devices?
> > >> 
> > > I must admit I never tried. Lack of maybe a couple sparse tables here
> > > and there?
> > >
> > > 
> > >> We tried raising the MAX_*_DEVICES constants in these files to 512, but
> > >> didn't have any luck:
> > >> linux-2.6-pvops.git/drivers/xen/blktap/blktap.h
> > >> tools/blktap2/include/blktaplib.h
> > >> tools/blktap/lib/blktaplib.h
> > >>
> > >> (The error is now "vbd open failed: -6")
> > >> 
> > > That would be an ENXIO, probably while trying to open the ring (can you
> > > verify that with an strace -f?)
> > > 
> > 
> > Looks like it is ENXIO:
> > 
> > ...
> > [pid 4154] open("/dev/xen/blktap-2/blktap256", O_RDWR <unfinished ...>
> > 
> > [pid 4153] close(4) = 0
> > [pid 4153] fcntl(3, F_GETFL) = 0 (flags O_RDONLY)
> > [pid 4153] brk(0) = 0xa1e000
> > [pid 4153] brk(0xa3f000) = 0xa3f000
> > [pid 4153] fstat(3, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
> > [pid 4153] mmap(NULL, 4096, PROT_READ|PROT_WRITE, 
> > MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f6844b40000
> > [pid 4153] lseek(3, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
> > [pid 4153] read(3, <unfinished ...>
> > 
> > [pid 4154] <... open resumed> ) = -1 ENXIO (No such device or 
> > address)
> > [pid 4154] gettimeofday({1271262219, 398530}, NULL) = 0
> > [pid 4154] sendto(0, "<27>Apr 14 09:23:39 tapdisk2[415"..., 115, 
> > MSG_NOSIGNAL, NULL, 0) = 115
> > [pid 4154] close(3) = 0
> > [pid 4154] gettimeofday({1271262219, 398836}, NULL) = 0
> > [pid 4154] sendto(0, "<30>Apr 14 09:23:39 tapdisk2[415"..., 109, 
> > MSG_NOSIGNAL, NULL, 0) = 109
> > [pid 4154] gettimeofday({1271262219, 399161}, NULL) = 0
> > [pid 4154] sendto(0, "<27>Apr 14 09:23:39 tapdisk2[415"..., 86, 
> > MSG_NOSIGNAL, NULL, 0) = 86
> > [pid 4154] write(1, "-6: vbd open failed: -6\n", 24) = 24
> > ... (err, ioctl to control, close and exit)
>
> Yep. So that's the ring device, which was apparently created ok but
> remains somehow inaccessible.
>
> Like I said, I think this fails earlier in the call stack than juyst
> blktap_ring_file_operations. Just from looking at some code I don't
> immediately see the issue.
>
> I guess this presently returns only halfway through chrdev_open. 
> Broken device registration somewhere? Does it take more magic to
> register minors beyond 8 bit?
Oh.
--snip
 * This function registers a range of 256 minor numbers. The first minor
number
 * is 0.
 */
int register_chrdev(unsigned int major, const char *name,
 const struct file_operations *fops)
--snip--
Judging from the rest of the kernel, we'll need to reimplement the
registration somewhat different that that.
Daniel
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