it may be a mess that if there is 2 btrfs partition (1 via bcache, 1 via dm) with same UUID appear at the same time. https://btrfs.wiki.kernel.org/index.php/Gotchas Currently, i think removing cache device would be simpler. On May 12, 2016 7:57:48 AM GMT+08:00, Marc MERLIN <marc@xxxxxxxxxxx> wrote: >On Thu, May 12, 2016 at 07:34:26AM +0800, ching wrote: >> for example >https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs-scrub > >btrfs scrub is designed to make sure all the blocks and checksums are >consistent. >Ching makes a good point that it would be helpful to have a way to >access the underlying backing device directly to ensure it is >consistent. > >I think currently you can use dmsetup with an offset to get the real >filesystem past the bcache header, mount that read only somewhere and >scrub that. >Not ideal because scrub will not be able to fix issues that are >fixable, >but at least it should report errors. > >Would that work? > >Marc > >> On May 12, 2016 3:13:22 AM GMT+08:00, Eric Wheeler ><bcache@xxxxxxxxxxxxxxxxxx> wrote: >> >On Wed, 11 May 2016, ching lu wrote: >> > >> >> The read cache prevent the program to scrub the backing device >> >directly. >> >> >> >> if a few bits flipped in the backing device, the cache may still >> >> return healthy data for a while. >> >> >> >> Must i remove cache device before scrubbing? >> > >> >What do you mean by scrub? >> > >> >-- >> >Eric Wheeler >> > >> >> >> >> >> >> On Wed, May 11, 2016 at 9:15 AM, Eric Wheeler >> ><bcache@xxxxxxxxxxxxxxxxxx> wrote: >> >> > On Fri, 29 Apr 2016, ching lu wrote: >> >> > >> >> >> Hello, >> >> >> >> >> >> i want to develop a script to perform data scrubbing >periodically. >> >> > >> >> > I think you want to set dirty_percent to 0 and >> >cache_mode=writethrough. >> >> > Then wait a long time for dirty_percent to actually reach 0. >> >> > >> >> > -- >> >> > Eric Wheeler >> >> > >> >> > >> >> >> >> >> >> For my use case, i think it is meaningless to scrub cached >data. >> >> >> >> >> >> If i change the cache mode to "none", will it turn off the read >> >cache too? >> >> >> >> >> >> Furthermore, will this invalidate cached data? (i do not want >to >> >"warm >> >> >> up" the cache again after the scrubbing) >> >> >> >> >> >> Thanks in advance, >> >> >> c >> >> >> -- >> >> >> To unsubscribe from this list: send the line "unsubscribe >> >linux-bcache" in >> >> >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> >> >> More majordomo info at >http://vger.kernel.org/majordomo-info.html >> >> >> >> >> -- >> >> To unsubscribe from this list: send the line "unsubscribe >> >linux-bcache" in >> >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe >linux-bcache" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
