Re: [BISECT] Kernel panic, RIP bitmap_create

[NeilBrown <neilb@suse.de>]

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On Wed, 2 May 2012 23:14:09 -0700 Karl Newman <siliconfiend@gmail.com> wrote:

> I'm not sure how to go about getting the full stack trace. The
> motherboard has no serial port, so that's not an option. Unless the
> kernel supports USB to serial adapters for that purpose, in which case
> I might be able to borrow a couple Keyspans. Or I could sit and try
> and transcribe the whole thing...(!) 

A photo with a digital camera is usually easiest.   If you have wired
ethernet you could possible set up net-console.
Add something like

netconsole=@192.168.1.8/eth0,6666@192.168.1.3/00:14:85:fc:3b:de
           ^my address            ^other host IP / ethernet

Then on other-host run

  nc -u -l -p 6666 | tee -a /tmp/log


> I'm a little nervous about
> tripping the all-zeros UUID bug again, although it only happened once
> and it doesn't seem to be related to that commit.

IF you apply


--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8140,7 +8140,8 @@ static int md_notify_reboot(struct notifier_block *this,
 
        for_each_mddev(mddev, tmp) {
                if (mddev_trylock(mddev)) {
-                       __md_stop_writes(mddev);
+                       if (mddev->pers)
+                               __md_stop_writes(mddev);
                        mddev->safemode = 2;
                        mddev_unlock(mddev);
                }


to the kernel before you build it, that bug should not happen again.


>    Anyway, here's some
> data from the array:

Thanks.  Nothing jumps out at me, but I'll ponder it some more.

Thanks,
NeilBrown



> 
> # mdadm -E /dev/sda3
> /dev/sda3:
>           Magic : a92b4efc
>         Version : 0.90.00
>            UUID : 60bf4ee8:e6e3e14f:073e21cd:ed2abb54
>   Creation Time : Wed May  2 20:22:47 2012
>      Raid Level : raid5
>   Used Dev Size : 29302400 (27.94 GiB 30.01 GB)
>      Array Size : 58604800 (55.89 GiB 60.01 GB)
>    Raid Devices : 3
>   Total Devices : 3
> Preferred Minor : 127
> 
>     Update Time : Wed May  2 23:01:45 2012
>           State : active
> Internal Bitmap : present
>  Active Devices : 3
> Working Devices : 3
>  Failed Devices : 0
>   Spare Devices : 0
>        Checksum : 863c968f - correct
>          Events : 2
> 
>          Layout : left-symmetric
>      Chunk Size : 128K
> 
>       Number   Major   Minor   RaidDevice State
> this     0       8        3        0      active sync   /dev/sda3
> 
>    0     0       8        3        0      active sync   /dev/sda3
>    1     1       8       19        1      active sync   /dev/sdb3
>    2     2       8       35        2      active sync   /dev/sdc3
> 
> # mdadm -X /dev/sda3
>         Filename : /dev/sda3
>            Magic : 6d746962
>          Version : 4
>             UUID : 60bf4ee8:e6e3e14f:073e21cd:ed2abb54
>           Events : 1
>   Events Cleared : 1
>            State : OK
>        Chunksize : 64 MB
>           Daemon : 5s flush period
>       Write Mode : Normal
>        Sync Size : 29302400 (27.94 GiB 30.01 GB)
>           Bitmap : 448 bits (chunks), 0 dirty (0.0%)


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