[arch-releng] squash FS error sometimes on ISOs

[Gerardo Exequiel Pozzi]

Dieter Plaetinck wrote:
> On Sun, 02 Aug 2009 14:35:32 -0300
> Gerardo Exequiel Pozzi <vmlinuz386 at yahoo.com.ar> wrote:
>
>   
>> Dan McGee wrote:
>>     
>>> On a slightly related note, take a look at the dmesg output on sigurd-
>>> something is acting up a bit:
>>>
>>> $ dmesg | tail
>>> ioctl32(grub:28054): Unknown cmd fd(3) cmd(00001261){t:12;sz:0}
>>> arg(00000000) on
>>> /home/archiso/install-iso/archlinux-2009.08-alpha-ftp-i686.img
>>> ioctl32(mke2fs:28828): Unknown cmd fd(3) cmd(80041272){t:12;sz:4}
>>> arg(ff810c40) on
>>> /home/archiso/install-iso/archlinux-2009.08-alpha-core-i686.img.part1
>>>
>>>   
>>>       
>> ioctl32 messages from kernel are triggered when you are running a x86-64
>> kernel, and when call an ioclt() from 32 bit user-space app with an
>> unsupported command (in other words when no conversion between 32 bit to
>> 64 bit ioctl). But only 50 of this messages are showed by the kernel,
>> next call just return -EINVAL
>>
>>     
>
> So, what does this mean? we call commands that don't exist, isn't that pretty bad?
> How does this affect iso building?
>
> Dieter
>
>   
Is a good question, but the answer is maybe difficult respond.

First, the ioctl is not executed at all. Second the program that call to
ioctl() with and unsupported cmd, in this enviroment, is probably that
manages the return status from the call to avoid problems, then in case
that is critical, the programs is sure that will be aborted instead of
continue running.

In this cite case 00001261 is

0 _IO (macro) (bits 31-30)
0x12 (driver) (15-8)
0x60 (function) (7-0) = 97 in decimal


$ grep -r "_IO(" . | grep 0x12 | grep 97
./include/linux/fs.h:#define BLKFLSBUF  _IO(0x12,97)    /* flush buffer
cache */

So no problem. (i guess)

and for 80041272

0x8 = 10 = _IOR
0x12 (driver)
0x72 (function)

./include/linux/fs.h:#define BLKGETSIZE64 _IOR(0x12,114,size_t) /*
return device size in bytes (u64 *arg) */

Probably the program will try another ioctl to get size if one fail, an
abort if can do it (i guess)


-- 
Gerardo Exequiel Pozzi ( djgera )
http://www.djgera.com.ar
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