On Thu, Apr 5, 2018 at 12:51 PM, Nikolaus Rath <nikol...@rath.org> wrote: > Hi Michael, > > Could you explain why this isn't a problem with writethrough? It seems > to me that the trouble happens when the hibernation image is *read*, so > why does it matter what kind of write caching is used?
With writethrough you can set up your loader to read it directly from the backing device-- e.g. you don't need the cache, and there's at least some valid configurations; with writeback some of the extents may be on the cache dev so... That said, it's not really great to put swap/hibernate on a cache device... the workloads don't usually benefit much from tiering (since they tend to be write-once-read-never or write-once-read-once). >> I am unaware of a mechanism to prohibit this in the kernel-- to say that >> a given type of block provider can't be involved in a resume operation. >> Most documentation for hibernation explicitly cautions about the btrfs >> situation, but use of bcache is less common and as a result generally >> isn't covered. > > Could you maybe add a warning to Documentation/bcache.txt? I think this > would have saved me. Yah, I can look at that. > > Best, > -Nikolaus Mike
