cd + geom -> panic on media change

[Andriy Gapon]

I had an Audio CD in a DVD drive.
I booted with that CD in and this is how it was reported:
cd0: <Optiarc DVD RW AD-7191S 1.02> Removable CD-ROM SCSI device
cd0: 150.000MB/s transfers (SATA 1.x, UDMA5, ATAPI 12bytes, PIO 8192bytes)
cd0: 392MB (200919 2048 byte sectors)

I see that there is some special code in scsi_cd.c that sets sector size to 2352
for Audio CDs, but that was not reflected in the report quoted above.

Later I popped out the CD (using the physical eject button, if that matters) and
popped in a UDF formatted DVD disk.  That resulted in the following panic:

panic: wrong offset 472559440 for sectorsize 2048
KDB: stack backtrace:
db_trace_self_wrapper() at 0xffffffff8043517b = db_trace_self_wrapper+0x2b/frame
0xfffffe0504bc8870
kdb_backtrace() at 0xffffffff80685289 = kdb_backtrace+0x39/frame 0xfffffe0504bc8920
vpanic() at 0xffffffff8064ce8c = vpanic+0x14c/frame 0xfffffe0504bc8960
panic() at 0xffffffff8064cbd3 = panic+0x43/frame 0xfffffe0504bc89c0
g_io_request() at 0xffffffff805c3b81 = g_io_request+0x3e1/frame 0xfffffe0504bc8a00
g_read_data() at 0xffffffff805c48e7 = g_read_data+0x77/frame 0xfffffe0504bc8a40
g_part_gpt_probe() at 0xffffffff805df0d1 = g_part_gpt_probe+0x111/frame
0xfffffe0504bc8a80
G_PART_PROBE() at 0xffffffff805daa0b = G_PART_PROBE+0x4b/frame 0xfffffe0504bc8aa0
g_part_probe() at 0xffffffff805da366 = g_part_probe+0xc6/frame 0xfffffe0504bc8af0
g_part_taste() at 0xffffffff805d8de7 = g_part_taste+0x147/frame 0xfffffe0504bc8b30
g_new_provider_event() at 0xffffffff805c7a0b = g_new_provider_event+0x10b/frame
0xfffffe0504bc8b50
one_event() at 0xffffffff805c2a4f = one_event+0xff/frame 0xfffffe0504bc8b70
g_run_events() at 0xffffffff805c2875 = g_run_events+0x65/frame 0xfffffe0504bc8b90
g_event_procbody() at 0xffffffff805c4f38 = g_event_procbody+0x58/frame
0xfffffe0504bc8ba0
fork_exit() at 0xffffffff80614800 = fork_exit+0xd0/frame 0xfffffe0504bc8bf0
fork_trampoline() at 0xffffffff80837a7e = fork_trampoline+0xe/frame
0xfffffe0504bc8bf0

The actual DVD has size 680368 x 2048.
I did some basic math and 472559440 == 200919 * 2352 - 2048.
Given that the code was probing GPT, the offset is consistent with mediasize
still being the old size of the Audio CD while the sector size being 2048.
Seems like the disk properties were not properly updated before posting the new
provider event.

Patches and suggestions are welcome :)
Thank you!

-- 
Andriy Gapon