(2013/11/25 23:41), Vivek Goyal wrote: > On Mon, Nov 25, 2013 at 06:01:37PM +0900, HATAYAMA Daisuke wrote: > > [..] >>> I agree to avoid this issue by fixing makedumpfile as workaround while to >>> fix kernel is so tough and risky. However, it sounds strange to me to fix >>> userspace side elaborately for such definite kernel issue whose cause is >>> known, so we should fix the kernel itself. >>> >> >>> Otherwise, will you continue to add specific fixes into user tools to >>> address kernel issues like this case ? >>> >> >> makedumpfile supports a wide range of kernel versions and needs to satisfy >> backward compatibility. mmap() on /proc/vmcore might be backported to some of >> the old versions on some distributions if necessary. Then, it's hard to fix >> each old kernel at each back port. The method that can be applied to all the >> kernels in general, is necessary. >> >> Also, looking at ia64 case where there's boot loader data on partial pages, >> there could be other environments where partial pages contain other important >> data other components have. So, the issue depends not only on kernels but also >> other components such as boot loader and firmwares that can put data on >> partial pages. We need to get there as long as there's important data there >> and we have access to there. > > Hi Atsushi, Hatayama, > > So even if we fix the mmap() issue in kernel, looks like it will be a > good idea to ship the fix in makedumpfile as there have been a kernel > release where mmap() will cause issues. > > Having said that, I think we need to fix it in kernel also. I was not sure > that what's the right fix. Should we truncate partial pages or should > we just copy partial pages from old memory to new kernel's memory and fill > partial page with zeros. And that's why I was hoping that makedumpfile > can fill the gap. > > Copying partial pages to new memory seems like a safer approach. So may > be we can take a fix in makeudmpfile and another in kernel. > > Hatayama, I know that in the past your initial mmap() patches were copying > partial pages to new kernel's memory. Would you like to resurrect that > patch again? > (Oh, I yesterday had totally forgotten partial page handling that was dropped from mmap() patch set in the middle of development...) Yes, but wait until next week. -- Thanks. HATAYAMA, Daisuke
