On 14 Jan 2018, Coly Li said: > Hi maintainers and folks, > > This patch set tries to improve bcache device failure handling, includes > cache device and backing device failures. > > The basic idea to handle failed cache device is, > - Unregister cache set > - Detach all backing devices which are attached to this cache set > - Stop all the detached bcache devices > - Stop all flash only volume on the cache set > The above process is named 'cache set retire' by me. The result of cache > set retire is, cache set and bcache devices are all removed, following > I/O requests will get failed immediately to notift upper layer or user > space coce that the cache device is failed or disconnected. This feels wrong to me. If a cache device is writethrough, the cache is a pure optimization: having such a device fail should not lead to I/O failures of any sort, but should only flip the cache device to 'none' so that writes to the backing store simply don't get cached any more. Anything else leads to a reliability reduction, since in the end cache devices *will* fail. -- NULL && (void)
