On 22/11/17 05:13, Michael Lyle wrote:

Reviewed-by: Michael Lyle <redacted>

<snip>

I have a little dilemma now related to this patch and I wonder if I 
could ask you guys for your opinion?

I have been hit and am being hit by the bug this patch fixes every few 
days at the moment, on writeback bcache resources. When it hits it 
causes a failure in the layer above, and this leads to other problems 
that can and has led to loss of data (not in bcache, just that the read 
failure causes a chain of events in upper layer, separate issue, won't 
clutter this mail with that). So, I am very keen to resolve this 
urgently in my environment.

I am running stable 4.9, and I have cherry picked several recent bcache 
patches, including "bcache: only permit to recovery read error
when cache device is clean", which I understand causes this issue.

I have a dilemma now whether I should apply the new patch in this 
thread, which should fix the issue, or revert "only permit to recovery 
read error" patch.

The dilemma is because I don't like the idea of reverting the "only 
permit to recovery read error" patch since it appears to fix an 
important problem.  Or am I overestimating the problem (maybe that's why 
the original patch has not been backported to stable kernels, maybe the 
original issue quite rare)?

But I am also wary of applying the new patch as Michael only just added 
to his tree so hasn't had much baking time.

I wondered what is the opinion of you guys which of these two I should 
choose?

(BTW, please don't say "just don't cherry pick onto 4.9". I am aware of 
the risks of cherry picking, as discussed recently on this list. I am 
happy with the level of risk and I am being very careful in what I pick. 
In this case I have not been "burnt" by cherry picking since I would 
have hit the same issue if I would have just upgraded to 4.14 which 
contains the original "only permit to recovery read error" patch.)

( N.B. I understand that any opinion/advice I receive is just that. I 
take complete responsibility for what I decide :-) )

Thanks!
Eddie