On Wed, Sep 15, 2021 at 05:22:27PM -0700, Darrick J. Wong wrote: > > xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED); > > ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, > > (write_fault && !vmf->cow_page) ? > > - &xfs_direct_write_iomap_ops : > > - &xfs_read_iomap_ops); > > + &xfs_dax_write_iomap_ops : > > + &xfs_read_iomap_ops); > > Hmm... I wonder if this should get hoisted to a "xfs_dax_iomap_fault" > wrapper like you did for xfs_iomap_zero_range?
This has just a single users, so the classic argument won't apply. That being said __xfs_filemap_fault is a complete mess to due the calling conventions of the various VFS methods multiplexed into it. So yes, splitting out a xfs_dax_iomap_fault to wrap the above plus the dax_finish_sync_fault call might not actually be a bad idea nevertheless. > > + struct xfs_inode *ip = XFS_I(inode); > > + /* > > + * Usually we use @written to indicate whether the operation was > > + * successful. But it is always positive or zero. The CoW needs the > > + * actual error code from actor(). So, get it from > > + * iomap_iter->processed. > > Hm. All six arguments are derived from the struct iomap_iter, so maybe > it makes more sense to pass that in? I'll poke around with this more > tomorrow. I'd argue against just changing the calling conventions for ->iomap_end now. The original iter patches from willy allowed passing a single next callback combinging iomap_begin and iomap_end in a way that with a little magic we can avoid the indirect calls entirely. I think we'll need to experiment with that that a bit and see if is worth the effort first. I plan to do that but I might not get to it immediate. If some else wants to take over I'm fine with that. > > static int > > xfs_buffered_write_iomap_begin( > > Also, we have an related request to drop the EXPERIMENTAL tag for > non-DAX reflink. Whichever patch enables dax+reflink for xfs needs to > make it clear that reflink + any possibility of DAX emits an > EXPERIMENTAL warning. More importantly before we can merge this series we also need the VM level support for reflink-aware reverse mapping. So while this series here is no in a good enough shape I don't see how we could merge it without that other series as we'd have to disallow mmap for reflink+dax files otherwise.