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* SD driver and 8KB HW sector size
@ 2004-10-29 15:18 Luka Renko
  2004-10-29 18:27 ` Brian King
  0 siblings, 1 reply; 3+ messages in thread
From: Luka Renko @ 2004-10-29 15:18 UTC (permalink / raw)
  To: linux-scsi; +Cc: Steve McIntyre, Damjan Lango

Hello,
 
SCSI Disk Driver in Linux 2.6 on i386 supports only devices with up-to 4KB
sector size. Large sector size is not supported by block layer as it is
expected that sector size is smaller or equal than page size (4KB).
 
We have a device (magneto-optical disk) that has 8 KB HW sector size. We
would like to use it from user space via SCSI Generic driver. The problem is
that SCSI Disk Driver claims this device and registers it as /dev/sd device.
This is not a big problem per-se (as raw CDB can be sent over SD driver
too), but causes problems to Linux partitioning code. In some cases (first
open() after disk change?), Linux partitioning code gets executed, which
causes Oops (FC2 kernel 2.6.5-1.358):
 
sda : READ CAPACITY failed.
sda : status=0, message=00, host=1, driver=00
sda : sense not available.
sda: Write Protect is off
sda: Mode Sense: 00 00 00 00
sda: asking for cache data failed
sda: assuming drive cache: write through
sda : READ CAPACITY failed.
sda : status=0, message=00, host=1, driver=00
sda : sense not available.
sda: Write Protect is off
sda: Mode Sense: 00 00 00 00
sda: asking for cache data failed
sda: assuming drive cache: write through
 sda:<1>Unable to handle kernel NULL pointer dereference at virtual address
00000000
 printing eip:
02143452
*pde = 00000000
Oops: 0002 [#1]
CPU:    0
EIP:    0060:[<02143452>]    Not tainted
EFLAGS: 00010287   (2.6.5-1.358)
EIP is at create_empty_buffers+0x14/0x54
eax: 00000000   ebx: 030adb20   ecx: 00000000   edx: 00000000
esi: 00000000   edi: 030adb20   ebp: 030adb20   esp: 06d42d24
ds: 007b   es: 007b   ss: 0068
Process udomkfs (pid: 8150, threadinfo=06d42000 task=05236eb0)
Stack: 00000000 030adb20 02143be1 00000046 09f8b77c 00000001 09f8b784
00002000
       00000001 0218f700 030adb20 00000000 09f8b77c 09f8b6e0 021467f1
09f8b778
       00000000 0212b9a7 00000000 030adb20 030adb20 09f8b778 0212b9de
00000000

Call Trace:
 [<02143be1>] block_read_full_page+0x4f/0x26e
 [<0218f700>] radix_tree_insert+0x6d/0xe2
 [<021467f1>] blkdev_get_block+0x0/0x47
 [<0212b9a7>] add_to_page_cache+0x3a/0x64
 [<0212b9de>] add_to_page_cache_lru+0xd/0x20
 [<0212cb5a>] read_cache_page+0x81/0x110
 [<021468e0>] blkdev_readpage+0x0/0xc
 [<02169bb1>] read_dev_sector+0x26/0x7c
 [<0216aca7>] read_lba+0x56/0x9b
 [<0216adb6>] alloc_read_gpt_header+0x4e/0x6b
 [<0216ae06>] is_gpt_valid+0x33/0x103
 [<0216b1fa>] find_valid_gpt+0x75/0x2de
 [<0216b48d>] efi_partition+0x2a/0x251
 [<0212ea1b>] __alloc_pages+0x9c/0x281
 [<02115ed2>] __wake_up_common+0x2f/0x50
 [<02115f01>] __wake_up+0xe/0x16
 [<021189cd>] printk+0x106/0x113
 [<021695ab>] disk_name+0x1f/0x60
 [<021696dd>] check_partition+0x8f/0xd1
 [<02169b06>] rescan_partitions+0x7d/0x102
 [<02146d95>] check_disk_change+0x3f/0x59
 [<0a8285e7>] sd_open+0xe3/0xf6 [sd_mod]
 [<0214706b>] do_open+0x24b/0x340
 [<021471e8>] blkdev_open+0x1a/0x46
 [<02140a6a>] dentry_open+0xc2/0x171
 [<021409a2>] filp_open+0x36/0x3c
 [<02140cde>] sys_open+0x31/0x7d

I have looked through the code and it seems to me that partitioning code
asumes in some places that sector size is 512 bytes. This might be OK on
CD-ROM or similar as they emulate 512 byte IO even with larger HW sector
sizes (if I remember correctly), however it does not work if we have a
device with > 4KB HW sector size.

I see two options to fix/workaround this problem:
1. Prevent partitioning code to be executed if block device does not support
proper sector size 
2. Prevent SCSI Disk driver to claim a device if sector size is not
supported
(in that case SCSI Generic driver should claim it)

We would like to explore one of the above options, but I would need some
advice from the mailing list which of the above would be a better way to
support such devices.

Regards,
Luka

^ permalink raw reply	[flat|nested] 3+ messages in thread
* RE: SD driver and 8KB HW sector size
@ 2004-11-08 15:14 Luka Renko
  0 siblings, 0 replies; 3+ messages in thread
From: Luka Renko @ 2004-11-08 15:14 UTC (permalink / raw)
  To: brking, Luka Renko; +Cc: linux-scsi, Steve McIntyre, Damjan Lango

2.5.10-rc1 looks OK (cannot reproduce). Thanks for info.

Regards,
Luka 

> -----Original Message-----
> From: Brian King [mailto:brking@us.ibm.com] 
> Sent: Friday, October 29, 2004 20:28
> To: Luka Renko
> Cc: linux-scsi@vger.kernel.org; Steve McIntyre; Damjan Lango
> Subject: Re: SD driver and 8KB HW sector size
> 
> Please try a 2.6.10-rc1 kernel. There was a fix that went in 
> recently for a problem I ran into that should fix your 
> problem as well.
> 
> -Brian
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2004-11-08 15:15 UTC | newest]

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2004-10-29 15:18 SD driver and 8KB HW sector size Luka Renko
2004-10-29 18:27 ` Brian King
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2004-11-08 15:14 Luka Renko

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