On 12/2/20 4:22 AM, Christoph Hellwig wrote: > 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. Hm, trying to parse that... Would it be correct to restate your last sentence as "Disallowing reflink when XFS_DIFLAG2_DAX is set and dax=inode is set makes sense?" If so, then the only change you're suggesting to this patch is to /allow/ reflinking if dax=never is set? I just figured a very clear statementa bout incompatible flags was simplest, but I get it that it's overly restrictive, functionally. Thanks, -Eric
