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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 09-01-2008, 11:00 AM
Tejun Heo
 
Default init: DEBUG_BLOCK_EXT_DEVT requires explicit root= param

DEBUG_BLOCK_EXT_DEVT shuffles SCSI and IDE device numbers and root
device number set using rdev become meaningless. Root devices should
be explicitly specified using textual names. Warn about it if root
can't be found and DEBUG_BLOCK_EXT_DEVT is enabled.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
---
There are other ways to specify device numbers directly (ie. root=8:0)
and DEBUG_BLOCK_EXT_DEVT being a debug option I don't think it
warrants a complex logic, so I just added simple warning message.

init/do_mounts.c | 4 ++++
1 file changed, 4 insertions(+)

Index: work/init/do_mounts.c
================================================== =================
--- work.orig/init/do_mounts.c
+++ work/init/do_mounts.c
@@ -263,6 +263,10 @@ retry:
printk("Please append a correct "root=" boot option; here are the available partitions:
");

printk_all_partitions();
+#ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
+ printk("DEBUG_BLOCK_EXT_DEVT is enabled, you need to specify "
+ "explicit textual name for "root=" boot option.
");
+#endif
panic("VFS: Unable to mount root fs on %s", b);
}


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Old 09-01-2008, 11:20 AM
Tejun Heo
 
Default init: DEBUG_BLOCK_EXT_DEVT requires explicit root= param

Jens Axboe wrote:
>> There are other ways to specify device numbers directly (ie. root=8:0)
>> and DEBUG_BLOCK_EXT_DEVT being a debug option I don't think it
>> warrants a complex logic, so I just added simple warning message.
>
> How about just putting that in the help entry as well? Given that it's
> now defaulting to 'n', people that enable it should read the help text
> anyway.

I'll add that to help message but I still think it'll be beneficial to
have warning message printed to avoid getting people off guard. e.g.
alpha/beta distro built with the debug option turned on to detect bugs.

Thanks.

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Old 09-01-2008, 11:38 AM
Tejun Heo
 
Default init: DEBUG_BLOCK_EXT_DEVT requires explicit root= param

DEBUG_BLOCK_EXT_DEVT shuffles SCSI and IDE device numbers and root
device number set using rdev become meaningless. Root devices should
be explicitly specified using textual names. Warn about it if root
can't be found and DEBUG_BLOCK_EXT_DEVT is enabled. Also, add warning
to the help text.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
---
I think distros should enable it for early alpha/betas to catch odd
problems. Well, anyways, here's the updated version. Thanks.

init/do_mounts.c | 4 ++++
lib/Kconfig.debug | 6 ++++++
2 files changed, 10 insertions(+)

Index: work/init/do_mounts.c
================================================== =================
--- work.orig/init/do_mounts.c
+++ work/init/do_mounts.c
@@ -263,6 +263,10 @@ retry:
printk("Please append a correct "root=" boot option; here are the available partitions:
");

printk_all_partitions();
+#ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
+ printk("DEBUG_BLOCK_EXT_DEVT is enabled, you need to specify "
+ "explicit textual name for "root=" boot option.
");
+#endif
panic("VFS: Unable to mount root fs on %s", b);
}

Index: work/lib/Kconfig.debug
================================================== =================
--- work.orig/lib/Kconfig.debug
+++ work/lib/Kconfig.debug
@@ -638,6 +638,12 @@ config DEBUG_BLOCK_EXT_DEVT
userland code paths which assume predetermined contiguous
device number allocation.

+ Note that turning on this debug option shuffles all the
+ device numbers for all IDE and SCSI devices including libata
+ ones, so root partition specified using device number
+ directly (via rdev or root=MAJ:MIN) won't work anymore.
+ Textual device names (root=/dev/sdXn) will continue to work.
+
Say N if you are unsure.

config LKDTM

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