On Fri, Oct 27, 2017 at 2:13 PM, Eric Wheeler [off-list ref] wrote:
[snip]

quoted

quoted

Can KEY_DIRTY facilitate this?

Don't we only have the metadata to know if the key is dirty on the
cache if we have the cache device? ;)

Certainly if this is for removal or a missing cache (perhaps I missed
that).

However, I thought this was just a recovery on an IO error where the disk
might be mostly dead--but partly alive!

Of course if the metadata lookup fails subsequently, then you would need
to fall back to the dc->has_dirty flag.

Seems like something that's a lot of effort for little gain.  It'll
only help when A) everything you need isn't dirty, and B) all the
associated btree nodes are in memory.  Since bcache tries to keep 10%
dirty by default, and it's likely to be heavy on filesystem metadata--
I don't know how often this would help anyone in the real world.

Mike