The patch titled
Subject: mm/mlock.c: document scary-looking stack expansion mlock chain
has been added to the -mm tree. Its filename is
mm-mlockc-document-scary-looking-stack-expansion-mlock-chain.patch
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From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm/mlock.c: document scary-looking stack expansion mlock chain
The fact that mlock calls get_user_pages, and get_user_pages might
call mlock when expanding a stack looks like a potential recursion.
However, mlock makes sure the requested range is already contained
within a vma, so no stack expansion will actually happen from mlock.
Should this ever change: the stack expansion mlocks only the newly
expanded range and so will not result in recursive expansion.
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mlock.c | 4 ++++
1 file changed, 4 insertions(+)
diff -puN mm/mlock.c~mm-mlockc-document-scary-looking-stack-expansion-mlock-chain mm/mlock.c
--- a/mm/mlock.c~mm-mlockc-document-scary-looking-stack-expansion-mlock-chain
+++ a/mm/mlock.c
@@ -185,6 +185,10 @@ long __mlock_vma_pages_range(struct vm_a
if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
gup_flags |= FOLL_FORCE;
+ /*
+ * We made sure addr is within a VMA, so the following will
+ * not result in a stack expansion that recurses back here.
+ */
return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
NULL, NULL, nonblocking);
}
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
memcg-fix-typo-in-kmemcg-cache-walk-macro.patch
linux-next.patch
mm-memcg-only-evict-file-pages-when-we-have-plenty.patch
mm-vmscan-save-work-scanning-almost-empty-lru-lists.patch
mm-vmscan-clarify-how-swappiness-highest-priority-memcg-interact.patch
mm-vmscan-improve-comment-on-low-page-cache-handling.patch
mm-vmscan-clean-up-get_scan_count.patch
mm-vmscan-clean-up-get_scan_count-fix.patch
mm-vmscan-compaction-works-against-zones-not-lruvecs.patch
mm-vmscan-compaction-works-against-zones-not-lruvecs-fix.patch
mm-reduce-rmap-overhead-for-ex-ksm-page-copies-created-on-swap-faults.patch
mm-page_allocc-__setup_per_zone_wmarks-make-min_pages-unsigned-long.patch
mm-vmscanc-__zone_reclaim-replace-max_t-with-max.patch
memcgvmscan-do-not-break-out-targeted-reclaim-without-reclaimed-pages.patch
mmotm-memcgvmscan-do-not-break-out-targeted-reclaim-without-reclaimed-pagespatch-fix-fix.patch
memcg-reduce-the-size-of-struct-memcg-244-fold.patch
memcg-reduce-the-size-of-struct-memcg-244-fold-fix.patch
memcg-prevent-changes-to-move_charge_at_immigrate-during-task-attach.patch
memcg-split-part-of-memcg-creation-to-css_online.patch
memcg-fast-hierarchy-aware-child-test.patch
memcg-fast-hierarchy-aware-child-test-fix.patch
memcg-replace-cgroup_lock-with-memcg-specific-memcg_lock.patch
memcg-increment-static-branch-right-after-limit-set.patch
memcg-avoid-dangling-reference-count-in-creation-failure.patch
mm-memmap_init_zone-performance-improvement.patch
mm-shmem-use-new-radix-tree-iterator.patch
mm-refactor-inactive_file_is_low-to-use-get_lru_size.patch
mm-mlockc-document-scary-looking-stack-expansion-mlock-chain.patch
memcg-debugging-facility-to-access-dangling-memcgs.patch
mm-prevent-addition-of-pages-to-swap-if-may_writepage-is-unset.patch
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