Re: [PATCH] userfaultfd/shmem: fix minor fault page leak
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2021-03-24 23:21:13
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linux-fsdevel, linux-kselftest, lkml
On Mon, 22 Mar 2021 13:48:35 -0700 Axel Rasmussen [off-list ref] 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:
quoted hunk ↗ jump to hunk
--- 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); *fault_type = handle_userfault(vmf, VM_UFFD_MINOR); return 0; }
Is added by Peter's "page && vma && userfaultfd_minor". I assume that "Fixes:" is incorrect?