Re: 2.6.0-test1 devfs question

Re: 2.6.0-test1 devfs question

["Andrey Borzenkov"]

> 
> The patch is broken - 2.4 does /dev/md/2 as well.
> 
> So what is the bug?  Why are people suddenly having problems with this?
> 

Daniele did some debugging, result is:

=================
Buggy config
------------
GRUB command line: kernel (hd0,1)/testing root=/dev/md2
video=radeonfb:1024x768-32@60
As output there is only (copied by hand):

[...]

raid1: raid set md2 active with 2 out of 2 mirrors
md: ... autorun DONE.
create_dev: name=/dev/root dev=902 dname=md2
VFS: cannot open root device "md2" or md2
please append a correct "root=" boot option
Kernel panic: VFS: unable to mount root fs on md2
<STOP>
==================

the bug is almost for sure in init/do_mount_devfs.c:read_dir; it
allocates static buffer of size at most 2**MAX_ORDER and tries to
read the whole dir at once. md driver creates all minors in md_init
i.e. 256 (2**MINORBITS). MAX_ORDER default is 11 so we have at most
2K which is enough for appr. 200 entries; 256 do not fit :)

Daniel, please, could you change read_dir to just allocate bigger
buffer - 4K should do - and test once more?

I'll see what can be done. Anyone sees reason why normal directory
scan won't work here?

-andrey 

Re: 2.6.0-test1 devfs question

[Andrew Morton]

"Andrey Borzenkov" <arvidjaar@mail.ru> wrote:
>
> the bug is almost for sure in init/do_mount_devfs.c:read_dir; it
>  allocates static buffer of size at most 2**MAX_ORDER and tries to
>  read the whole dir at once.

Yes, that function is buggy.

diff -puN init/do_mounts_devfs.c~read_dir-fix init/do_mounts_devfs.c
--- 25/init/do_mounts_devfs.c~read_dir-fix	2003-07-28 00:21:40.000000000 -0700
+++ 25-akpm/init/do_mounts_devfs.c	2003-07-28 00:21:40.000000000 -0700
@@ -54,7 +54,7 @@ static void * __init read_dir(char *path
 	if (fd < 0)
 		return NULL;
 
-	for (size = 1 << 9; size <= (1 << MAX_ORDER); size <<= 1) {
+	for (size = 1 << 9; size <= (PAGE_SIZE << MAX_ORDER); size <<= 1) {
 		void *p = kmalloc(size, GFP_KERNEL);
 		int n;
 		if (!p)

_

Re: [BUG SQUISHED] 2.6.0-test1 devfs question

[Daniele Venzano]

On Mon, Jul 28, 2003 at 12:22:16AM -0700, Andrew Morton wrote:
> "Andrey Borzenkov" <arvidjaar@mail.ru> wrote:
> >
> > the bug is almost for sure in init/do_mount_devfs.c:read_dir; it
> >  allocates static buffer of size at most 2**MAX_ORDER and tries to
> >  read the whole dir at once.
> 
> Yes, that function is buggy.
> 
> diff -puN init/do_mounts_devfs.c~read_dir-fix init/do_mounts_devfs.c
> --- 25/init/do_mounts_devfs.c~read_dir-fix	2003-07-28 00:21:40.000000000 -0700
> +++ 25-akpm/init/do_mounts_devfs.c	2003-07-28 00:21:40.000000000 -0700
> @@ -54,7 +54,7 @@ static void * __init read_dir(char *path
>  	if (fd < 0)
>  		return NULL;
>  
> -	for (size = 1 << 9; size <= (1 << MAX_ORDER); size <<= 1) {
> +	for (size = 1 << 9; size <= (PAGE_SIZE << MAX_ORDER); size <<= 1) {
>  		void *p = kmalloc(size, GFP_KERNEL);
>  		int n;
>  		if (!p)
> 
> _

This patch solves the problem, the kernel boots fine and finds the root
device using root=/dev/md2 as boot option.

The output during boot is:

[...]
raid1: raid set md2 active with 2 out of 2 mirrors
md: ... autorun DONE.
create_dev: name=/dev/root dev=902 dname=md2
create_dev: found real device /dev/md/2
[...]

Thanks everyone, bye.

-- 
----------------------------------------
Daniele Venzano
Web: http://digilander.iol.it/webvenza/