On Tue, Feb 26, 2019 at 08:35:46PM +0800, Ming Lei wrote: > On Tue, Feb 26, 2019 at 04:12:09AM -0800, Matthew Wilcox wrote: > > On Tue, Feb 26, 2019 at 07:12:49PM +0800, Ming Lei wrote: > > > The buffer needs to be device block size aligned for dio, and now the block > > > size can be 512, 1024, 2048 and 4096. > > > > Why does the block size make a difference? This requirement is due to > > some storage devices having shoddy DMA controllers. Are you saying there > > are devices which can't even do 512-byte aligned I/O? > > Direct IO requires that, see do_blockdev_direct_IO(). > > This issue can be triggered when running xfs over loop/dio. We could > fallback to buffered IO under this situation, but not sure it is the > only case. Wait, we're imposing a ridiculous amount of complexity on XFS for no reason at all? We should just change this to 512-byte alignment. Tying it to the blocksize of the device never made any sense.
