Hi Hannes, I'm very sorry for the huge delay, but please see below. On 2009/04/28 16:49 +0900, Kiyoshi Ueda wrote: > Hi Hannes, > > On 2009/04/24 17:59 +0900, Hannes Reinecke wrote: >> Hi Kiyoshi, >> >> Kiyoshi Ueda wrote: >>> This patch detects requests violating the queue limitations >>> and rejects them. >>> >>> The same limitation checks are done when requests are submitted >>> to the queue by blk_insert_cloned_request(). >>> However, such violation can happen if a table is swapped and >>> the queue limitations are shrunk while some requests are >>> in the queue. >>> >>> Since struct request is a reliable one in the block layer and >>> device drivers, dispatching such requests is pretty dangerous. >>> (e.g. it may cause kernel panic easily.) >>> So avoid to dispatch such problematic requests in request-based dm. >>> >> This patch actually triggers accidentally during a no-paths scenario; >> multipathing seems to flush all device details once all paths are gone, >> so it'll fall back to the system defaults. >> And then this check will trigger and kill all queued I/Os. Not good. >> >> So either we fix device-mapper to keep the device details even for >> the all-paths down scenario (basically we'd have to copy the device >> details into the target_io structures and use that for comparison) >> or we should rather not check here. > > Thank you for your review and the comment. > I haven't understood the problem correctly yet. > (e.g. Who flush the device details and how? Restrictions are > changed when the table is swapped, but no table swapping should happen > even if the last path is gone while the device is in use.) I tried to understand/reproduce your scenario, but I can't. I found a bug (http://marc.info/?l=dm-devel&m=124572577028515&w=2) during my testing (which lets all paths down at once), but it is an user-space bug, not a kernel bug. Could you elaborate your problem related to the patch, if you have detailed analisys? (e.g. I can't see the code-path which flushes device details on an all-paths down scenario.) Thanks, Kiyoshi Ueda -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
