On Mon, 22 Mar 2021 13:48:35 -0700 Axel Rasmussen axelrasmussen@google.com wrote:
This fix is analogous to Peter Xu's fix for hugetlb [0]. If we don't put_page() after getting the page out of the page cache, we leak the reference.
The fix can be verified by checking /proc/meminfo and running the userfaultfd selftest in shmem mode. Without the fix, we see MemFree / MemAvailable steadily decreasing with each run of the test. With the fix, memory is correctly freed after the test program exits.
Fixes: 00da60b9d0a0 ("userfaultfd: support minor fault handling for shmem")
Confused. The affected code:
--- a/mm/shmem.c +++ b/mm/shmem.c @@ -1831,6 +1831,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, if (page && vma && userfaultfd_minor(vma)) { unlock_page(page);
put_page(page);
Is added by Peter's "page && vma && userfaultfd_minor". I assume that "Fixes:" is incorrect?