On Thu, Dec 06, 2018 at 07:51:52AM -0500, Brian Foster wrote: > On Wed, Dec 05, 2018 at 02:51:47PM -0800, Christoph Hellwig wrote: > > XFS currently uses kmalloc for buffers smaller than the page size to > > avoid wasting too much memory. But this can cause a problem with slub > > debugging turned on as the allocations might not be naturally aligned. > > On block devices that require sector size alignment this can lead to > > data corruption. > > > > Give that our smaller than page size buffers are always sector sized > > on a live file system, we can just create a kmem_cache with an > > explicitly specified alignment requirement for this case to fix this > > case without much effort. > > > > What exactly is the data corruption related problem? Can you > characterize it in a couple sentences? Ming reported the actual occurance, so he can explain in detail. But the summary is that various devices require a minimum alignment for DMA, and if we don't follow that bad things will happen. What "bad things" are might vary from case to case.
