[dm-devel] [PATCH] bcache: never writeback a discard operation

[Daniel Axtens]

Hi Sasha,

> This commit has been processed because it contains a "Fixes:" tag,
> fixing commit: 72c270612bd3 bcache: Write out full stripes.

I added that fixes tag because that was the commit that added the
code. However, I noticed that one of the bug reports mentions that the
problem only arising after v4.8. [1] I don't quite know what to make of
this: perhaps it is a consequence of another change enabling the broken
path. Maybe someone on one of the lists will have an idea.

> v4.4.171: Build failed! Errors:
>     drivers/md/bcache/writeback.h:71:6: error: implicit declaration of function ‘bio_op’; did you mean ‘bio_rw’? [-Werror=implicit-function-declaration]
>     drivers/md/bcache/writeback.h:71:21: error: ‘REQ_OP_DISCARD’ undeclared (first use in this function); did you mean ‘REQ_DISCARD’?
>
> v3.18.132: Build failed! Errors:
>     drivers/md/bcache/writeback.h:71:6: error: implicit declaration of function ‘bio_op’; did you mean ‘bio_rw’? [-Werror=implicit-function-declaration]
>     drivers/md/bcache/writeback.h:71:21: error: ‘REQ_OP_DISCARD’ undeclared (first use in this function); did you mean ‘REQ_DISCARD’?
>
>
> How should we proceed with this patch?

The patch seems reasonably easy to backport. Compile-tested only, and
only against v4.4.171.

Regards,
Daniel

[1] https://bugzilla.kernel.org/show_bug.cgi?id=196103

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