On Tue, Sep 4, 2012 at 4:46 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 4 Sep 2012 16:39:49 -0700 > Michel Lespinasse <walken@xxxxxxxxxx> wrote: > >> This change fixes an anon_vma locking issue in the following situation: >> - vma has no anon_vma >> - next has an anon_vma >> - vma is being shrunk / next is being expanded, due to an mprotect call >> >> We need to take next's anon_vma lock to avoid races with rmap users >> (such as page migration) while next is being expanded. > > hm, OK. How serious was that bug? I'm suspecting "only needed in > 3.7". That was my starting position as well. I'd expect the biggest issue would be page migration races, and we do have assertions for that case, and we've not been hitting them (that I know of). So, this should not be a high frequency issue AFAICT. I don't want to push for -stable backports myself, but I do think it's nice to do a minimal patch so that it can easily be backported if we decide to. -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies. -- 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>