On Tue, Dec 01, 2020 at 01:20:55PM -0600, Eric Sandeen wrote: > Today, xfs_reflink_remap_prep() will reject inodes which are in the CPU > direct access state, i.e. IS_DAX() is true. However, it is possible to > have inodes with the XFS_DIFLAG2_DAX set, but which are not activated as > dax, due to the dax=never mount option, or due to the flag being set after > the inode was loaded. > > To avoid confusion and make the lack of dax+reflink crystal clear for the > user, reject reflink requests for both IS_DAX and XFS_DIFLAG2_DAX inodes. > > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> > --- > > This is RFC because as Darrick says, it introduces a new failure mode for > reflink. On the flip side, today the user can reflink a chattr +x'd file, > but cannot chattr +x a reflinked file, which seems a best a bit asymmetrical > and confusing... see xfs_ioctl_setattr_xflags() This seems confusing. IMHO for now we should just for non-dax access to any reflink file even if XFS_DIFLAG2_DAX is set. The only place where we cannot do that is if a file has XFS_DIFLAG2_DAX set and is in use and we want to reflink it. Note that "in use" is kinda murky and potentially racy. So IMHO not allowing reflink when XFS_DIFLAG2_DAX is set and dax=never is not set makes sense, but we should not go further.
