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. -- 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
