lib: radix-tree: check accounting of existing slot replacement users
The bug in khugepaged fixed earlier in this series shows that radix tree
slot replacement is fragile; and it will become more so when not only
NULL<->!NULL transitions need to be caught but transitions from and to
exceptional entries as well. We need checks.
Re-implement radix_tree_replace_slot() on top of the sanity-checked
__radix_tree_replace(). This requires existing callers to also pass the
radix tree root, but it'll warn us when somebody replaces slots with
contents that need proper accounting (transitions between NULL entries,
real entries, exceptional entries) and where a replacement through the
slot pointer would corrupt the radix tree node counts.
Link: http://lkml.kernel.org/r/20161117193021.GB23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/filemap.c b/mm/filemap.c
index caa779f..1ba726a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -147,7 +147,7 @@
false);
}
}
- radix_tree_replace_slot(slot, page);
+ radix_tree_replace_slot(&mapping->page_tree, slot, page);
mapping->nrpages++;
if (node) {
workingset_node_pages_inc(node);
@@ -196,7 +196,7 @@
shadow = NULL;
}
- radix_tree_replace_slot(slot, shadow);
+ radix_tree_replace_slot(&mapping->page_tree, slot, shadow);
if (!node)
break;
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5d7c006..7a50c72 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1426,7 +1426,7 @@
list_add_tail(&page->lru, &pagelist);
/* Finally, replace with the new page. */
- radix_tree_replace_slot(slot,
+ radix_tree_replace_slot(&mapping->page_tree, slot,
new_page + (index % HPAGE_PMD_NR));
slot = radix_tree_iter_next(&iter);
@@ -1538,7 +1538,8 @@
/* Unfreeze the page. */
list_del(&page->lru);
page_ref_unfreeze(page, 2);
- radix_tree_replace_slot(slot, page);
+ radix_tree_replace_slot(&mapping->page_tree,
+ slot, page);
spin_unlock_irq(&mapping->tree_lock);
putback_lru_page(page);
unlock_page(page);
diff --git a/mm/migrate.c b/mm/migrate.c
index 66ce6b4..0ed24b1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -482,7 +482,7 @@
SetPageDirty(newpage);
}
- radix_tree_replace_slot(pslot, newpage);
+ radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
/*
* Drop cache reference from old page by unfreezing
@@ -556,7 +556,7 @@
get_page(newpage);
- radix_tree_replace_slot(pslot, newpage);
+ radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
page_ref_unfreeze(page, expected_count - 1);
diff --git a/mm/truncate.c b/mm/truncate.c
index 8d8c62d..3c631c3 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -49,7 +49,7 @@
goto unlock;
if (*slot != entry)
goto unlock;
- radix_tree_replace_slot(slot, NULL);
+ radix_tree_replace_slot(&mapping->page_tree, slot, NULL);
mapping->nrexceptional--;
if (!node)
goto unlock;