The patch titled
only drop root anon_vma if not self (kmemleak)
has been added to the -mm tree. Its filename is
mm-extend-ksm-refcounts-to-the-anon_vma-root-fix.patch
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------------------------------------------------------
Subject: only drop root anon_vma if not self (kmemleak)
From: Rik van Riel <riel@xxxxxxxxxx>
With the new anon_vma code we take a refcount on the root anon_vma.
However, the root anon_vma does not have a refcount on itself, so
we should not try to do a drop on itself when it is being unlinked.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Tested-by: Dave Young <hidave.darkstar@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 3 ++-
mm/rmap.c.orig | 45 ++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 46 insertions(+), 2 deletions(-)
diff -puN mm/rmap.c~mm-extend-ksm-refcounts-to-the-anon_vma-root-fix mm/rmap.c
--- a/mm/rmap.c~mm-extend-ksm-refcounts-to-the-anon_vma-root-fix
+++ a/mm/rmap.c
@@ -273,7 +273,8 @@ static void anon_vma_unlink(struct anon_
if (empty) {
/* We no longer need the root anon_vma */
- drop_anon_vma(anon_vma->root);
+ if (anon_vma->root != anon_vma)
+ drop_anon_vma(anon_vma->root);
anon_vma_free(anon_vma);
}
}
diff -puN mm/rmap.c.orig~mm-extend-ksm-refcounts-to-the-anon_vma-root-fix mm/rmap.c.orig
--- a/mm/rmap.c.orig~mm-extend-ksm-refcounts-to-the-anon_vma-root-fix
+++ a/mm/rmap.c.orig
@@ -236,6 +236,12 @@ int anon_vma_fork(struct vm_area_struct
* lock any of the anon_vmas in this anon_vma tree.
*/
anon_vma->root = pvma->anon_vma->root;
+ /*
+ * With KSM refcounts, an anon_vma can stay around longer than the
+ * process it belongs to. The root anon_vma needs to be pinned
+ * until this anon_vma is freed, because the lock lives in the root.
+ */
+ get_anon_vma(anon_vma->root);
/* Mark this anon_vma as the one where our new (COWed) pages go. */
vma->anon_vma = anon_vma;
anon_vma_chain_link(vma, avc, anon_vma);
@@ -265,8 +271,11 @@ static void anon_vma_unlink(struct anon_
empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);
anon_vma_unlock(anon_vma);
- if (empty)
+ if (empty) {
+ /* We no longer need the root anon_vma */
+ drop_anon_vma(anon_vma->root);
anon_vma_free(anon_vma);
+ }
}
void unlink_anon_vmas(struct vm_area_struct *vma)
@@ -1398,6 +1407,40 @@ int try_to_munlock(struct page *page)
return try_to_unmap_file(page, TTU_MUNLOCK);
}
+#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
+/*
+ * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root
+ * if necessary. Be careful to do all the tests under the lock. Once
+ * we know we are the last user, nobody else can get a reference and we
+ * can do the freeing without the lock.
+ */
+void drop_anon_vma(struct anon_vma *anon_vma)
+{
+ if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
+ struct anon_vma *root = anon_vma->root;
+ int empty = list_empty(&anon_vma->head);
+ int last_root_user = 0;
+ int root_empty = 0;
+
+ /*
+ * The refcount on a non-root anon_vma got dropped. Drop
+ * the refcount on the root and check if we need to free it.
+ */
+ if (empty && anon_vma != root) {
+ last_root_user = atomic_dec_and_test(&root->external_refcount);
+ root_empty = list_empty(&root->head);
+ }
+ anon_vma_unlock(anon_vma);
+
+ if (empty) {
+ anon_vma_free(anon_vma);
+ if (root_empty && last_root_user)
+ anon_vma_free(root);
+ }
+ }
+}
+#endif
+
#ifdef CONFIG_MIGRATION
/*
* rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
_
Patches currently in -mm which might be from riel@xxxxxxxxxx are
mm-rename-anon_vma_lock-to-vma_lock_anon_vma.patch
mm-change-direct-call-of-spin_lockanon_vma-lock-to-inline-function.patch
mm-track-the-root-oldest-anon_vma.patch
mm-track-the-root-oldest-anon_vma-fix.patch
mm-always-lock-the-root-oldest-anon_vma.patch
mm-extend-ksm-refcounts-to-the-anon_vma-root.patch
mm-extend-ksm-refcounts-to-the-anon_vma-root-fix.patch
oom-filter-tasks-not-sharing-the-same-cpuset.patch
oom-sacrifice-child-with-highest-badness-score-for-parent.patch
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