> -----Original Message----- > From: linux-btrfs-ow...@vger.kernel.org <linux-btrfs- > ow...@vger.kernel.org> On Behalf Of Qu Wenruo > Sent: Thursday, 28 June 2018 5:16 PM > To: Nikolay Borisov <nbori...@suse.com>; Qu Wenruo <w...@suse.com>; > linux-btrfs@vger.kernel.org > Subject: Re: [PATCH RFC] btrfs: Do extra device generation check at mount > time > > > > On 2018年06月28日 15:06, Nikolay Borisov wrote: > > > > > > On 28.06.2018 10:04, Qu Wenruo wrote: > >> There is a reporter considering btrfs raid1 has a major design flaw > >> which can't handle nodatasum files. > >> > >> Despite his incorrect expectation, btrfs indeed doesn't handle device > >> generation mismatch well. > >> > >> This means if one devices missed and re-appeared, even its generation > >> no longer matches with the rest device pool, btrfs does nothing to > >> it, but treat it as normal good device. > >> > >> At least let's detect such generation mismatch and avoid mounting the > >> fs. > >> Currently there is no automatic rebuild yet, which means if users > >> find device generation mismatch error message, they can only mount > >> the fs using "device" and "degraded" mount option (if possible), then > >> replace the offending device to manually "rebuild" the fs. > >> > >> Signed-off-by: Qu Wenruo <w...@suse.com> > > > > I think a testcase of this functionality is important as well. > > It's currently an RFC patch, test case would come along with final version. > > I'd like to make sure everyone, including developers and end-users, are fine > with the restrict error-out behavior.
I've been bitten by this before and was most surprised the first time it happened. I had assumed that of course btrfs would check such a thing before mounting. Refusing to mount is a great first step, auto scrub is even better, and only "scrubbing" files with incorrect generation is better yet. Paul.
