On Thu, Feb 08, 2018 at 02:48:52PM -0500, Daniel Micay wrote: > I guess it could saturate and then switch to tracking the count via an > object pointer -> count mapping with a global lock? Whatever the > solution is should probably be a generic one since it's a recurring > issue. I was thinking of saturating _mapcount at 2 billion (allowing _refcount the extra space to go into the 2-3 billion range). Once saturated, disallow all attempts at mapping it until _mapcount has gone below 2 billion again. We can walk the page->mapping->i_mmap tree and find tasks with more than, say, 10 mappings each, and kill them. Now that I think about it, though, perhaps the simplest solution is not to worry about checking whether _mapcount has saturated, and instead when adding a new mmap, check whether this task already has it mapped 10 times. If so, refuse the mapping. Now we can argue that since pid_max is smaller than 400 million that _mapcount will never overflow, and so we don't need to check it. Convincing argument? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
