On 2/27/19 10:32 PM, Oscar Salvador wrote: > On Tue, Feb 26, 2019 at 02:04:28PM -0800, Andrew Morton wrote: >> How is this going to affect existing userspace which is aware of the >> current behaviour? > > Well, current behavior is not really predictable. > Our customer was "surprised" that the call to mremap() failed, but the regions > got unmapped nevertheless. > They found it the hard way when they got a segfault when trying to write to those > regions when cleaning up. > > As I said in the changelog, the possibility for false positives exists, due to > the fact that we might get rid of several vma's when unmapping, but I do not > expect existing userspace applications to start failing. > Should be that the case, we can revert the patch, it is not that it adds a lot > of churn. Hopefully the only program that would start failing would be a LTP test testing the current behavior near the limit (if such test exists). And that can be adjusted. >> And how does it affect your existing cleanup code, come to that? Does >> it work as well or better after this change? > > I guess the customer can trust more reliable that the maps were left untouched. > I still have my reserves though. > > We can get as far as move_vma(), and copy_vma() can fail returning -ENOMEM. > (Or not due to the "too small to fail" ?) >
