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authorJohannes Weiner <hannes@cmpxchg.org>2016-12-12 16:43:52 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-12 18:55:08 -0800
commit14b468791fa955d442f962fdf5207dfd39a131c8 (patch)
treea1a5a3d445b7de16ae06184fa9c0804e3255d9d2 /mm/truncate.c
parent4d693d08607ab319095ec8942909df4b4aebdf66 (diff)
mm: workingset: move shadow entry tracking to radix tree exceptional tracking
Currently, we track the shadow entries in the page cache in the upper bits of the radix_tree_node->count, behind the back of the radix tree implementation. Because the radix tree code has no awareness of them, we rely on random subtleties throughout the implementation (such as the node->count != 1 check in the shrinking code, which is meant to exclude multi-entry nodes but also happens to skip nodes with only one shadow entry, as that's accounted in the upper bits). This is error prone and has, in fact, caused the bug fixed in d3798ae8c6f3 ("mm: filemap: don't plant shadow entries without radix tree node"). To remove these subtleties, this patch moves shadow entry tracking from the upper bits of node->count to the existing counter for exceptional entries. node->count goes back to being a simple counter of valid entries in the tree node and can be shrunk to a single byte. This vastly simplifies the page cache code. All accounting happens natively inside the radix tree implementation, and maintaining the LRU linkage of shadow nodes is consolidated into a single function in the workingset code that is called for leaf nodes affected by a change in the page cache tree. This also removes the last user of the __radix_delete_node() return value. Eliminate it. Link: http://lkml.kernel.org/r/20161117193211.GE23430@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> 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>
Diffstat (limited to 'mm/truncate.c')
-rw-r--r--mm/truncate.c21
1 files changed, 3 insertions, 18 deletions
diff --git a/mm/truncate.c b/mm/truncate.c
index 3c631c357873..fd97f1dbce29 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -44,28 +44,13 @@ static void clear_exceptional_entry(struct address_space *mapping,
* without the tree itself locked. These unlocked entries
* need verification under the tree lock.
*/
- if (!__radix_tree_lookup(&mapping->page_tree, index, &node,
- &slot))
+ if (!__radix_tree_lookup(&mapping->page_tree, index, &node, &slot))
goto unlock;
if (*slot != entry)
goto unlock;
- radix_tree_replace_slot(&mapping->page_tree, slot, NULL);
+ __radix_tree_replace(&mapping->page_tree, node, slot, NULL,
+ workingset_update_node, mapping);
mapping->nrexceptional--;
- if (!node)
- goto unlock;
- workingset_node_shadows_dec(node);
- /*
- * Don't track node without shadow entries.
- *
- * Avoid acquiring the list_lru lock if already untracked.
- * The list_empty() test is safe as node->private_list is
- * protected by mapping->tree_lock.
- */
- if (!workingset_node_shadows(node) &&
- !list_empty(&node->private_list))
- list_lru_del(&workingset_shadow_nodes,
- &node->private_list);
- __radix_tree_delete_node(&mapping->page_tree, node);
unlock:
spin_unlock_irq(&mapping->tree_lock);
}