[DRBD-user] 2.6.14-1.1656_FC4 kernel with drbd hangs (was: mkfs hangs)

Philipp Reisner philipp.reisner at linbit.com
Thu Jan 26 10:43:24 CET 2006

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Am Dienstag, 24. Januar 2006 02:38 schrieb Todd Denniston:
> I have found a way to consistently cause the hang with 2.6.14-1.1656_FC4 &
> drbd, and I believe I have enough results to say the fault is related to
> Neil Brown's "reduce stack consumption" patch.  I say related because I
> don't know enough to determine if Neil's patch is 'rude & evil' :) or if
> DRBD just happens to exercise the bio's in a way that his email[2]
> indicates are "unsafe".
> The question I still have now is:
> Is this a problem that should be fixed in the kernel, i.e., Neil or others
> resubmit the patch again, or is it some unsafeness in DRBD which must be
> fixed? (Finger pointing can now begin :)

Hi Todd,

First I want to thank you for that great preparation work! You pointed
at the right patch, you provided instructions for reproducing the
problem, that is exactly what developers like.

Ad finger pointing
Well, Neil Brown's patch changes the kernel's API semantics, and none
of the in-tree drivers cared. 
I point my finger to Fedora, why do they apply such patches to their
distribution kernel, while this patch has not yet found it way into
the vanilla kernel ? -- My feeling was that distributor's kernels
should be even more conservative than the vanilla kernel. But the
sad truth is, that distributions try to set each other apart by
providing more and more bleeding edge features. 
  OTOH Fedora people help me to shake out bugs, before the causing
  patches arrive in the vanilla kernel. Nice.

Could you please provide feedback, if this patch (applies to drbd-0.7.15)
fixes the problem for you ?

: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
: Schönbrunnerstr 244, 1120 Vienna, Austria    http://www.linbit.com :
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