On Mon, Mar 19, 2018 at 10:57:55AM -0700, Dan Williams wrote: > On Mon, Mar 19, 2018 at 10:33 AM, Darrick J. Wong > <darrick.wong@xxxxxxxxxx> wrote: > > On Thu, Mar 15, 2018 at 08:52:29AM -0700, Dan Williams wrote: > >> In preparation for adding coordination between truncate operations and > >> busy dax-pages, extend xfs_break_layouts() to assume it must be called > >> with the mmap lock held. This locking scheme will be required for > >> coordinating the break of 'dax layouts' (non-idle dax (ZONE_DEVICE) > >> pages mapped into the file's address space). > > > > If I'm reading this right, you've added a requirement (for xfs anyway) > > that we have to have grabbed MMAPLOCK_EXCL before calling break_layout() > > so that the layout breaking process will block until active dmas have > > finished. > > > > In 4.16 we added xfs_iolock_two_inodes_and_break_layout (in > > xfs_reflink.c) to break pnfs leases for files that are about to be > > reflinked (since pnfs and reflink aren't compatible either). I think > > that function will have to be adapted to take the appropriate mmap locks > > too -- definitely the exclusive mmap lock for the destination file > > because we anticipate punching out blocks. I'm not sure about the > > source file; I think taking the shared mmap lock is fine for that? > > I don't see anything to adapt with respect to mmap locks since reflink > and dax are mutually exclusive. The new lock coordination and layout > breaking in xfs_break_dax_layouts() only applies to dax vs truncate, > so xfs_iolock_two_inodes_and_break_layout() looks ok to me as is. I was aiming for DAX + reflink someday working together. :) As far as that goes, I think the only thing we really have to do is figure out how to make iomap_begin do the cow operation before letting userspace write to (or MAP_SYNC a writable region) pmem, right? --D > -- > 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
