On Sat, Apr 01, 2017 at 08:34:58AM +0200, Christoph Hellwig wrote: > commit 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e upstream. > > We currently fall back from direct to buffered writes if we detect a > remaining shared extent in the iomap_begin callback. But by the time > iomap_begin is called for the potentially unaligned end block we might > have already written most of the data to disk, which we'd now write > again using buffered I/O. To avoid this reject all writes to reflinked > files before starting I/O so that we are guaranteed to only write the > data once. > > The alternative would be to unshare the unaligned start and/or end block > before doing the I/O. I think that's doable, and will actually be > required to support reflinks on DAX file system. But it will take a > little more time and I'd rather get rid of the double write ASAP. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx> > Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Any specific reason you don't want this one in 4.9 as well? Just curious, greg k-h -- 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
