Re: md= broken. Found problem. Can't fix it. : (

[Sandy Harris]

Dave Cinege wrote:
> 
> ... 'md=' for each device on
> the cmdline, but unfortuantly it's broken.
> 
> Between a few emails to mingo and several wasted hours, I've managed to figure
> out the problem. However I don't know how to fix it; it *should*
> be working from what I can see.
> 
> My only guess right now is because I'm using gcc 2.95.2, and it's doing
> something funky. (And I do not have another version to test with right now.)
> 
> The problem is during parsing of the md= line, name_to_kdev_t() is not
> returning the proper k_dev_t for the device. (IE /dev/sdd5 returns as
> 16:45 /dev/sde5 returns as 20:05.)

Looks to me like this parsing code unnecessarily and rather clumsily re-invents
strtok() and should be rewritten to use that function. It takes two nested loops,
along the general lines of:

/*
outer loop, parse into space-separted strings
*/
for( p = strtok(str, " ") ; p != NULL ; p = strtok(NULL, " ")   {
/*
inner loop using comma separator
*
for( q = strtok( p, ",") ; q != NULL ; q = strtok(NULL, ","){

}
}

I suspect that I've misunderstood some constraint here. Perhaps the more complex
code you posted is necessary, but I'd like to know why.
 
> However if I pass static text to name_to_kdev_t(), it works. I first believed
> it was in how the str pointer was sent to name_to_kdev_t(), (running over into
> comma's, instead of seperate terminated strings) I
> fixed that but the problem persists.
> 
> My current test for loop is attached. The hard coded device names
> printk out to a proper major:minor. The devicenames obtained from
> 'str' don't. I don't see the bug in here or name_to_kdev_t()...
> 
> I'm testing this with the following cmdline:
> root=/dev/md0 raid=noautodetect md=0,/dev/hdd5,/dev/hde5
> md=1,/dev/hdd6,/dev/hde6  md=2,/dev/hdd7,/dev/hde7
> md=3,/dev/hdd8,/dev/hde8 mem=524288K
> 
> --
> "Nobody will ever be safe until the last cop is dead."
> NH Rep. Tom Alciere - (My new Hero)
> 
>   
>
> 2.4.1prepatch 8
> drivers/md/md.c line 3722
> 
> for (; i < MD_SB_DISKS && str; i++) {
> /*
> if ((device = name_to_kdev_t(str))) {
> md_setup_args.devices[minor][i] = device;
> } else {
> printk ("md: Unknown device name, %s.\n", str);
> return 0;
> }
> if ((str = strchr(str, ',')) != NULL)
> str++;
> */
> 
> char *ndevstr;
> ndevstr = strchr(str, ','); // Goto ','
> if (ndevstr != NULL)
> *ndevstr++ = 0; // Zero it for proper string
> 
> // DEBUG Print device name
> printk("Checking: '%s'\n", str);
> 
> 
> // Convert device name to k_dev_t and assign to md_setup_args.devices
> // DEBUG As test, hardcode device names for /dev/md0.0 and /dev/md0.1
> if (minor == 0 && i == 0)
> md_setup_args.devices[minor][i] = 
>name_to_kdev_t("/dev/sdd5");
> else if (minor == 0 && i == 1)
> md_setup_args.devices[minor][i] = 
>name_to_kdev_t("/dev/sde5");
> else
> md_setup_args.devices[minor][i] = name_to_kdev_t(str);
> 
> // DEBUG Print out kdevname of md_setup_args.devices
> printk("\t%s\n", kdevname(md_setup_args.devices[minor][i]));
> // DEBUG Print minor and i (insync?)
> printk("minor=%d, i=%d\n",minor, i);
> 
> // name_to_kdev_t() returned 0. Invalid device
> if (md_setup_args.devices[minor][i] == 0) {
> printk ("md: Unknown device name, %s.\n", str);
> return 0;
> }
> // Jump to next devname in str
> str = ndevstr;
> }
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Re: md= broken. Found problem. Can't fix it. : (

[Andi Kleen]

On Sat, Jan 20, 2001 at 04:58:56PM -0500, Sandy Harris wrote:
> I suspect that I've misunderstood some constraint here. Perhaps the more complex
> code you posted is necessary, but I'd like to know why.

strtok is not reentrant and cannot be nested this way without 
saving __strtok. strsep would work.


-Andi

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Re: md= broken. Found problem. Can't fix it. : (

[Dave Cinege]

Sandy Harris wrote:
> Looks to me like this parsing code unnecessarily and rather clumsily 
> re-invents strtok

The original parsing code is this:
if ((str = strchr(str, ',')) != NULL)
str++;
Which effectivly steps through
/dev/sda1,/dev/sdab1,/dev/sdc1
like this
str == /dev/sda1,/dev/sdab1,/dev/sdc1
str == /dev/sdab1,/dev/sdc1
str == /dev/sdc1

My code:char *ndevstr;
ndevstr = strchr(str, ',');
if (ndevstr != NULL)*ndevstr++ = 0; 
...
str = ndevstr

Works perfectly. I don't find it 'clumsy' or more complex at all. (I don't care
for strtok, nor did I even know the kernel had it)


However I don't see this critique of coding style helping the problem I'm
seeing:

name_to_kdev_t(str);
Returns a bad value. Yet
name_to_kdev_t("/dev/sdd5");
does not. The strange thing is
printk("Checking: '%s'\n", str);
shows str does infact contain a proper string.

It appears str does not get passed to name_to_kdev_t() properly,
and I have no idea why. Both my testing code and the original code
exhibit the same problem.


-- 
"Nobody will ever be safe until the last cop is dead."
NH Rep. Tom Alciere - (My new Hero)
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Re: md= broken. Found problem. Can't fix it. : (

[Dave Cinege]

Douglas Gilbert wrote:
> 
> Dave,
> Look at the dmesg output and check that your
> "Kernel command line:" is what you think it
> is. Some older versions of lilo truncate it.
> Here is mine (which is what I expected):
> 
> Kernel command line: auto BOOT_IMAGE=lin240 ro root=803 scsihosts=imm:advansys:a
> dvansys:aha1542

No that is not the problem. I'm using GRUB (LILO == poopoo) and 
have looked at this throughly.

I can see from the dmesg via my debugging printk's output that str is properly
being passed. 

-- 
"Nobody will ever be safe until the last cop is dead."
NH Rep. Tom Alciere - (My new Hero)
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Re: md= broken. Found problem. Can't fix it. : (

[Ingo Oeser]

On Sat, Jan 20, 2001 at 11:28:51PM +0100, Andi Kleen wrote:
> On Sat, Jan 20, 2001 at 04:58:56PM -0500, Sandy Harris wrote:
> > I suspect that I've misunderstood some constraint here. Perhaps the more complex
> > code you posted is necessary, but I'd like to know why.
> 
> strtok is not reentrant and cannot be nested this way without 
> saving __strtok. strsep would work.

But be careful:

strsep() in kernel skips zero length strings, but strsep 
glibc wouldn't do.

Regards

Ingo Oeser

Note: I implemented it to replace strtok and even did a patch to
   replace all occourences of it, but got no response and so stopped
   working on this issue. If there is still interest, I would do
   it again.
-- 
10.+11.03.2001 - 3. Chemnitzer LinuxTag 
    come and join the fun   
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