Hi, Andrew,
On Wed, Mar 24, 2021 at 04:20:27PM -0700, Andrew Morton wrote:
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?
It seems to me the commit is correct as pointed to in "Fixes", but I do have a different commit ID here:
commit 63c826b1372c4930f89b8a55092699fa7f0d6f4e Author: Axel Rasmussen axelrasmussen@google.com Date: Thu Mar 18 10:20:43 2021 -0400
userfaultfd: support minor fault handling for shmem
Axel, did you fetched the commit ID from your local tree, perhaps? Since I should have fetched from hnaz/linux-mm and I can see Andrew's sign-off too.
Thanks,