On Mon, Jun 21, 2010 at 03:16:08PM +0200, Andrea Arcangeli wrote: > > KOSAKI Motohiro get_user_pages vs COW problem > > Just a side note, not sure exactly what is meant to be discussed about > this bug, considering the fact this is still unsolved isn't technical > problem as there were plenty of fixes available, and the one that seem > to had better chance to get included was the worst one in my view, as > it tried to fix it in a couple of gup caller (but failed, also because > finding all put_page pin release is kind of a pain as they're spread > all over the place and not identified as gup_put_page, and in addition > to the instability and lack of completeness of the fix, it was also > the most inefficient as it added unnecessary and coarse locking) plus > all gup callers are affected, not just a few. I normally call it gup > vs fork race. Luckily not all threaded apps uses O_DIRECT and fork and > pretend to do the direct-io in different sub-page chunks of the same > page from different threads (KVM would probably be affected if it > didn't use MADV_DONTFORK on the O_DIRECT memory, as it might run fork > to execute some network script when adding an hotplug pci net device > for example). But surely we can discuss the fix we prefer for this > bug, or at least we can agree it needs fixing. > KVM is actually affected by the bug. The fix was posted today: http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg36759.html -- Gleb. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>