Re: [Nbd] NBD, DISCARD/TRIM

[folkert <folkert@...421...>]

> I had suspected the kill_bdev patch, as it's the only thing of any
> significance that has changed recently related to nbd shutdown, but it

As a note: this does not happen during shutdown. Well, maybe it does but
that was not invoked at the time of the crash.
The test was:
 mount /dev/nbd0 /mnt -o noatime,discard,barrier=1  (or without -o)
 and then on that mountpoint
 iozone3 [...]

> seems that this is something that has just broken in ext3/ext4. Even
> with kill_bdev calls removed, I still see BUGs (I think the same one
> you reported [mine is fs/buffer.c:2958]) and NULL ptr derefs in jbd
> when I abort the nbd connection with a mounted filesystem.
> Do you know or can you (or anyone else) check when this started?

Kernel 3.2 also exhibits this sudden:

	[  489.655034] block nbd0: shutting down socket
	[  489.655093] end_request: I/O error, dev nbd0, sector 358648
	[  489.655571] block nbd0: queue cleared

errors but no crashes.

> As for what is causing your client to stop in the first place, I'm not
> sure. How do you have the FS mounted? Are you testing discard, i.e.,
> you have the option enabled in the nbd-server?

As I wrote above.
But also with just plain mount /dev/nbd0 /mnt. This is always with a
filesystem build with mkfs.ext4 -j. Furthermore, this is with the stock
nbd-server (yes and with my nbd server but let's ignore that one for
now). I always mount with noatime and I only test with iozone (iozone3
package in debian).

iozone -j 1024 -s 2g -r 128k -I -f test -+w 7

nbd device is 16GB


Folkert van Heusden

-- 
MultiTail er et flexible tool for å kontrolere Logfiles og commandoer.
Med filtrer, farger, sammenføringer, forskeliger ansikter etc.
http://www.vanheusden.com/multitail/
----------------------------------------------------------------------
Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com