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SubjectPartition check considered as error is breaking mounting in 2.6.27
Date
[ Sent again now with correct CC to linux-usb ]

Hi,

Recently I found a problem with a buggy camera that doesn't mount anymore with
2.6.27 (its memory is available via usb-storage), since commit
04ebd4aee52b06a2c38127d9208546e5b96f3a19

The camera is an Olympus X-840. The original issue comes from the camera
itself: its format program creates a partition with an off by one error,
while the device reports that its memory has 42079 sectors, the partition
table reports also that the only partition on the disk has the size of 42079,
but it fails to account for the first sector in the memory that contains the
partition table, so in the end the partition exceeds the limit of the device
size (42080, first sector plus 42079 from the first partition).

In previous kernels (2.6.26 and before), I still could mount and access the
device (/dev/sdb1), although with the following errors:

sd 6:0:0:0: [sdb] Assuming drive cache: write through
sdb: sdb1
sdb: p1 exceeds device capacity
sd 6:0:0:0: [sdb] Attached SCSI removable disk
sd 6:0:0:0: Attached scsi generic sg2 type 0
usb-storage: device scan complete
attempt to access beyond end of device
sdb: rw=0, want=42080, limit=42079
__ratelimit: 16 messages suppressed
Buffer I/O error on device sdb1, logical block 42078
attempt to access beyond end of device
sdb: rw=0, want=42080, limit=42079

If you note the log snippet above the first notable thing is "p1 exceeds
device capacity", so looking at commit
04ebd4aee52b06a2c38127d9208546e5b96f3a19 it is clear why sdb1 isn't created
anymore.

After formatting the camera is this you get from fdisk (display units in
sectors):

Disk /dev/sdb: 21 MB, 21544448 bytes
6 heads, 16 sectors/track, 438 cylinders, total 42079 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x00000000

Device Boot Start End Blocks Id System
/dev/sdb1 * 1 42079 21039+ 1 FAT12
Partition 1 has different physical/logical endings:
phys=(328, 5, 16) logical=(438, 1, 16)

Note the bogus reported CHS values, both physical and logical, but they don't
affect anything here.

I don't know if this change of behaviour in 2.6.27 is desired (not creating
partition nodes if its size exceeds media size). Anyway the device is buggy
itself. Until now the only way I found to mount device inside 2.6.27 is using
hexedit to edit directly the partition table on the device, decreasing by 1
the length of the first partition (42079 -> 42078). Clearing the partition
table and using fdisk to partition again is not an option, the camera
firmware seems to be lost after this, it starts to report weird media size
(not by 1 sector error only):

attempt to access beyond end of device
sdb: rw=0, want=42042, limit=42000
attempt to access beyond end of device
sdb: rw=0, want=42042, limit=42000

Disk /dev/sdb: 21 MB, 21504000 bytes
1 heads, 42 sectors/track, 1000 cylinders, total 42000 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x57ea65f0

Device Boot Start End Blocks Id System
/dev/sdb1 42 42041 21000 1 FAT12

(after zeroing out the partition table I only run fdisk on the device, created
the a new partition with maximum size allowed and change the type to FAT12)

On both cases respectively this is relevant info that I get with usb-storage
debugging turned on:

* With memory formatted by camera firmware:
usb-storage: queuecommand called
usb-storage: *** thread awakened.
usb-storage: Command READ_CAPACITY (10 bytes)
usb-storage: 25 00 00 00 00 00 00 00 00 00
usb-storage: Bulk Command S 0x43425355 T 0x3 L 8 F 128 Trg 0 LUN 0 CL 10
usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes
usb-storage: Status code 0; transferred 31/31
usb-storage: -- transfer complete
usb-storage: Bulk command transfer result=0
usb-storage: usb_stor_bulk_transfer_sglist: xfer 8 bytes, 1 entries
usb-storage: Status code 0; transferred 8/8
usb-storage: -- transfer complete
usb-storage: Bulk data transfer result 0x0
usb-storage: Attempting to get CSW...
usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes
usb-storage: Status code 0; transferred 13/13
usb-storage: -- transfer complete
usb-storage: Bulk status result = 0
usb-storage: Bulk Status S 0x53425355 T 0x3 R 0 Stat 0x0
usb-storage: scsi cmd done, result=0x0
usb-storage: *** thread sleeping.
sd 4:0:0:0: [sdb] 42079 512-byte hardware sectors (22 MB)

* With partition table recreated with fdisk and formated by hand:
usb-storage: queuecommand called
usb-storage: *** thread awakened.
usb-storage: Command READ_CAPACITY (10 bytes)
usb-storage: 25 00 00 00 00 00 00 00 00 00
usb-storage: Bulk Command S 0x43425355 T 0x3 L 8 F 128 Trg 0 LUN 0 CL 10
usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes
usb-storage: Status code 0; transferred 31/31
usb-storage: -- transfer complete
usb-storage: Bulk command transfer result=0
usb-storage: usb_stor_bulk_transfer_sglist: xfer 8 bytes, 1 entries
usb-storage: Status code 0; transferred 8/8
usb-storage: -- transfer complete
usb-storage: Bulk data transfer result 0x0
usb-storage: Attempting to get CSW...
usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes
usb-storage: Status code 0; transferred 13/13
usb-storage: -- transfer complete
usb-storage: Bulk status result = 0
usb-storage: Bulk Status S 0x53425355 T 0x3 R 0 Stat 0x0
usb-storage: scsi cmd done, result=0x0
usb-storage: *** thread sleeping.
sd 6:0:0:0: [sdb] 42000 512-byte hardware sectors (22 MB)

After looking at all this I'm in doubt on what fix could be made in this case.
May be reverting the fatal error when partition exceeds media size? Or adding
a new usb-storage quirk to report media size with one more sector (dangerous,
but physically I don't know what's the real media size as firmware reports a
way different value of media size after using fdisk), or quirk to force
something in partition creation to automatically trim partition size by -1.

Any ideas?

More info about the device, may be it's useful:

T: Bus=03 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#= 2 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=07b4 ProdID=0109 Rev= 1.00
S: Manufacturer=OLYMPUS
S: Product=FE310,X840,C530
S: SerialNumber=Y31013411
C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA
I:* If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
E: Ad=02(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=82(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms

Bus 003 Device 003: ID 07b4:0109 Olympus Optical Co., Ltd C-370Z/D-535Z/X-450
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x07b4 Olympus Optical Co., Ltd
idProduct 0x0109 C-370Z/D-535Z/X-450
bcdDevice 1.00
iManufacturer 1 OLYMPUS
iProduct 2 FE310,X840,C530
iSerial 3 Y31013411
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 32
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xc0
Self Powered
MaxPower 0mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 8 Mass Storage
bInterfaceSubClass 6 SCSI
bInterfaceProtocol 80 Bulk (Zip)
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Device Status: 0x0001
Self Powered

--
[]'s
Herton


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