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Date: Fri, 19 Dec 2003 14:00:29 -0800
From: "Randy.Dunlap" <rddunlap@osdl.org>
To: elgaard@agol.dk
Cc: linux-kernel@vger.kernel.org
Subject: Re: Problem loopmounting CD on 2.6.0
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On Fri, 19 Dec 2003 14:10:44 +0100 Niels Elgaard Larsen <elgaard@agol.dk> wrote:

| A similar (probably the same) problem have been reported for cryptoloop.
| With a ISO9660 CD (actually Knoppix) in drive /dev/hdc, no SCSI emulation:
| 
| amigos20:/mnt# losetup /dev/loop5 /dev/hdc
| amigos20:/mnt# mount -r /dev/loop5 /mnt/foo
| 
| Gives kernel output:
| 
| ===
| hdc: cdrom_read_intr: data underrun (2 blocks)
| end_request: I/O error, dev hdc, sector 64
| isofs_fill_super: bread failed, dev=loop5, iso_blknum=16, block=32
| ===
| 
| It works in 2.4.20
| 
| Also
| 
| dd if=/dev/hdc of=/tmp/foo
| losetup /dev/loop5 /tmp/foo
| mount -r /dev/loop5 /mnt/foo
| 
| works

I see differing sector size and block size reports by blockdev
as follows.  Is this OK/expected or does it hint at a problem?

(all without ide-scsi:)

2.6.0, non-loopback case:

# mount
/dev/hdd on /mnt/disk type iso9660 (ro)

[root@gargoyle rddunlap]# blockdev --getss /dev/hdd
2048
[root@gargoyle rddunlap]# blockdev --getbsz  /dev/hdd
2048


2.6.0, loopback case:

I usually see the same error that you reported.
I did mount the cdrom successfully one time, with about 50
error messages like below[1], and saw this blocksize difference:
Is this OK or indicative of a (the) problem?


[root@gargoyle rddunlap]# blockdev --getss /dev/hdd
2048
[root@gargoyle rddunlap]# blockdev --getbsz  /dev/hdd
4096


[1]
hdd: cdrom_read_intr: data underrun (2 blocks)
end_request: I/O error, dev hdd, sector 64
hdd: cdrom_read_intr: data underrun (2 blocks)
end_request: I/O error, dev hdd, sector 68
hdd: cdrom_read_intr: data underrun (2 blocks)
end_request: I/O error, dev hdd, sector 72
...
hdd: cdrom_read_intr: data underrun (2 blocks)
end_request: I/O error, dev hdd, sector 388
hdd: cdrom_read_intr: data underrun (2 blocks)
end_request: I/O error, dev hdd, sector 392
hdd: cdrom_read_intr: data underrun (2 blocks)
end_request: I/O error, dev hdd, sector 396

2.4.2x:

[root@gargoyle rddunlap]# blockdev --getss /dev/hdd
512
[root@gargoyle rddunlap]# blockdev --getbsz  /dev/hdd
2048


--
~Randy
MOTD:  Always include version info.