On Thu, Oct 27, 2022 at 10:14:59AM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > As we've seen, refcount records use the upper bit of the rc_startblock > field to ensure that all the refcount records are at the right side of > the refcount btree. This works because an AG is never allowed to have > more than (1U << 31) blocks in it. If we ever encounter a filesystem > claiming to have that many blocks, we absolutely do not want reflink > touching it at all. > > However, this test at the start of xfs_refcount_recover_cow_leftovers is > slightly incorrect -- it /should/ be checking that agblocks isn't larger > than the XFS_MAX_CRC_AG_BLOCKS constant, and it should check that the > constant is never large enough to conflict with that CoW flag. > > Note that the V5 superblock verifier has not historically rejected > filesystems where agblocks <= XFS_MAX_CRC_AG_BLOCKS, which is why this ITYM >= > ended up in the COW recovery routine. I think we should probably fix that - I didn't realise we had this superblock geometry check buried deep in the reflink recovery code. That said, for the moment adding an extra check to the reflink recovery code is fine. Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> -- Dave Chinner david@xxxxxxxxxxxxx
