On Thu, Oct 05, 2017 at 09:16:34AM +1100, Dave Chinner wrote: > On Wed, Oct 04, 2017 at 11:02:04AM -0700, Darrick J. Wong wrote: > > On Wed, Oct 04, 2017 at 05:43:33PM +1100, Dave Chinner wrote: > > > It seems to me that we're using the superblock 0 values as the > > > golden master because it's a mounted filesystem, and then comparing > > > everything else against it. Maybe we should at least check a couple > > > of secondary superblocks to see that they match the primary > > > superblock - that way we'll have some confidence that at least > > > things like agcount, agblocks, dblocks, etc are valid before we go > > > any further... > > > > xfs_scrub_superblock does check the secondary superblock geometry > > against whatever's in mp->m_sb, which came from sb 0. > > /me smacks forehead > > The patch is even named "scrub the backup superblocks". > > Perhaps it didn't sink in because they are normally called > "secondary superblocks". My bad.... Sometimes I think I still have ext4 on the brain. :( --D > > > BUt maybe all we need is comment in the overall scrub description - > > > that we're pretty much assuming that sb 0 is intact because we write > > > what is in memory back to it and so we can simply validate > > > everything else against the primary superblock contents... > > > > Correct. Since scrub is run against a mounted live filesystem we assume > > that the mount code fully validated sb 0 and therefore we can rely on it > > not being wrong. > > > > If OTOH sb 0 *is* wrong then the admin is better off running xfs_repair > > because there's too much whirring machinery to go changing fundamental > > geometry. > > Yup, that makes sense. > > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" 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-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
