* Ryan Roberts <ryan.roberts@xxxxxxx> [230711 10:09]: > On 20/01/2023 16:26, Liam R. Howlett wrote: > > From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> > > > > Use the vma iterator so that the iterator can be invalidated or updated > > to avoid each caller doing so. > > Hi, Hello! > > I've bisected 2 mm selftest regressions back to this patch, so hoping someone can help debug and fix? The failures are reproducible on x86_64 and arm64. Thanks! That is a big help. Where did you start your bisection? I assume 6.4? > > > mlock-random-test: > > $ ./run_kselftest.sh -t mm:mlock-random-test > TAP version 13 > 1..1 > # selftests: mm: mlock-random-test > mlock() failure at |0xaaaaaaab52d0(131072)| mlock:|0xaaaaaaacc65d(26551)| > not ok 1 selftests: mm: mlock-random-test # exit=255 > > This mallocs a buffer then loops 100 times, trying to mlock random parts of it. After this patch, the test fails after a variable number of iterations; mlock() returns ENOMEM. If I explicitly munlock at the end of each loop, it works. > > > mlock2-tests: > > $ ./run_kselftest.sh -t mm:mlock2-tests > TAP version 13 > 1..1 > # selftests: mm: mlock2-tests > munlock(): Cannot allocate memory > munlock(): Cannot allocate memory > not ok 1 selftests: mm: mlock2-tests # exit=2 > > Here, a 3 page buffer is mlock2()ed, then the middle page is munlocked. Finally the whole 3 page range is munlocked, and after this patch it fails with ENOMEM. If I modify the test to split the final munlock into 2, one for the first page and one for the last, the test passes. > > > Immediately prior to this patch (2286a6914c77 "mm: change mprotect_fixup to vma iterator"), both tests pass. > > From a quick scan of the man page, I don't think it explicitly says that its ok to call mlock/munlock on already locked/unlocked pages, but it's certainly a change of behavior and the tests notice, so I'm guessing this wasn't intentional? > > I'm not familiar with this code so it's not obvious to me exactly what the problem is, but I'm hoping someone can help debug? I think I see the issue and I'm working on a fix. I appreciate the analysis and report, it really helps narrow things down. Regards, Liam
