Quoting Josef Bacik (2013-05-31 09:29:07) > On Fri, May 31, 2013 at 12:24:30AM -0600, Zach Brown wrote: > > > Changing O_DIRECT in flight has always been a deep dark corner case, and > > > crc errors are the expected result. Have you found anyone doing this in > > > real life? > > > > Agreed; and no, I haven't heard of people accidentally modifying stable > > pages. > > > > Windows does this, it also will send down the same page for different offsets > which is why we have that special check in check_direct_IO for reads because > that would cause lots of csum errors too. I tried to fix the modified in flight > problem by checking the csums of the pages in the io completion handler and > re-submitting the IO if the pages had changed, but this of course dramatically > reduced performance for all of those well behaved O_DIRECT applications, so in > the end I just set nodatasum for that vm image and carried on. I'm not sure > what the solution is for this problem. Thanks, Ugh, I forgot about the windows case. KVM should really be copying the pages for sectors where IO is already in flight. We could do the copies ourselves: mount -o dio_copies -chris -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
