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authorMatthew Wilcox <mawilcox@microsoft.com>2016-12-14 15:08:55 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-14 16:04:10 -0800
commit268f42de718128cd0301293177e79c08c38e39a6 (patch)
tree6668c85388c327f64ce9b51e77d70e245ec52b57 /lib
parent478922e2b0f41567e4a530771bfb3f693f857d45 (diff)
downloadlinux-stericsson-268f42de718128cd0301293177e79c08c38e39a6.tar.gz
radix-tree: delete radix_tree_range_tag_if_tagged()
This is an exceptionally complicated function with just one caller (tag_pages_for_writeback). We devote a large portion of the runtime of the test suite to testing this one function which has one caller. By introducing the new function radix_tree_iter_tag_set(), we can eliminate all of the complexity while keeping the performance. The caller can now use a fairly standard radix_tree_for_each() loop, and it doesn't need to worry about tricksy things like 'start' wrapping. The test suite continues to spend a large amount of time investigating this function, but now it's testing the underlying primitives such as radix_tree_iter_resume() and the radix_tree_for_each_tagged() iterator which are also used by other parts of the kernel. Link: http://lkml.kernel.org/r/1480369871-5271-57-git-send-email-mawilcox@linuxonhyperv.com Signed-off-by: Matthew Wilcox <willy@infradead.org> Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/radix-tree.c117
1 files changed, 20 insertions, 97 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 5bdf1bdbca00..d1f4ca5b7989 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -219,6 +219,11 @@ radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
return RADIX_TREE_MAP_SIZE;
}
+static unsigned int iter_offset(const struct radix_tree_iter *iter)
+{
+ return (iter->index >> iter_shift(iter)) & RADIX_TREE_MAP_MASK;
+}
+
/*
* The maximum index which can be stored in a radix tree
*/
@@ -1015,6 +1020,18 @@ static void node_tag_set(struct radix_tree_root *root,
}
/**
+ * radix_tree_iter_tag_set - set a tag on the current iterator entry
+ * @root: radix tree root
+ * @iter: iterator state
+ * @tag: tag to set
+ */
+void radix_tree_iter_tag_set(struct radix_tree_root *root,
+ const struct radix_tree_iter *iter, unsigned int tag)
+{
+ node_tag_set(root, iter->node, tag, iter_offset(iter));
+}
+
+/**
* radix_tree_tag_clear - clear a tag on a radix tree node
* @root: radix tree root
* @index: index key
@@ -1164,6 +1181,7 @@ void ** __radix_tree_next_slot(void **slot, struct radix_tree_iter *iter,
if (node == RADIX_TREE_RETRY)
return slot;
node = entry_to_node(node);
+ iter->node = node;
iter->shift = node->shift;
if (flags & RADIX_TREE_ITER_TAGGED) {
@@ -1266,6 +1284,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
iter->index = index;
iter->next_index = maxindex + 1;
iter->tags = 1;
+ iter->node = NULL;
__set_iter_shift(iter, 0);
return (void **)&root->rnode;
}
@@ -1308,6 +1327,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
/* Update the iterator state */
iter->index = (index &~ node_maxindex(node)) | (offset << node->shift);
iter->next_index = (index | node_maxindex(node)) + 1;
+ iter->node = node;
__set_iter_shift(iter, node->shift);
if (flags & RADIX_TREE_ITER_TAGGED)
@@ -1318,103 +1338,6 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
EXPORT_SYMBOL(radix_tree_next_chunk);
/**
- * radix_tree_range_tag_if_tagged - for each item in given range set given
- * tag if item has another tag set
- * @root: radix tree root
- * @first_indexp: pointer to a starting index of a range to scan
- * @last_index: last index of a range to scan
- * @nr_to_tag: maximum number items to tag
- * @iftag: tag index to test
- * @settag: tag index to set if tested tag is set
- *
- * This function scans range of radix tree from first_index to last_index
- * (inclusive). For each item in the range if iftag is set, the function sets
- * also settag. The function stops either after tagging nr_to_tag items or
- * after reaching last_index.
- *
- * The tags must be set from the leaf level only and propagated back up the
- * path to the root. We must do this so that we resolve the full path before
- * setting any tags on intermediate nodes. If we set tags as we descend, then
- * we can get to the leaf node and find that the index that has the iftag
- * set is outside the range we are scanning. This reults in dangling tags and
- * can lead to problems with later tag operations (e.g. livelocks on lookups).
- *
- * The function returns the number of leaves where the tag was set and sets
- * *first_indexp to the first unscanned index.
- * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
- * be prepared to handle that.
- */
-unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
- unsigned long *first_indexp, unsigned long last_index,
- unsigned long nr_to_tag,
- unsigned int iftag, unsigned int settag)
-{
- struct radix_tree_node *node, *child;
- unsigned long maxindex;
- unsigned long tagged = 0;
- unsigned long index = *first_indexp;
-
- radix_tree_load_root(root, &child, &maxindex);
- last_index = min(last_index, maxindex);
- if (index > last_index)
- return 0;
- if (!nr_to_tag)
- return 0;
- if (!root_tag_get(root, iftag)) {
- *first_indexp = last_index + 1;
- return 0;
- }
- if (!radix_tree_is_internal_node(child)) {
- *first_indexp = last_index + 1;
- root_tag_set(root, settag);
- return 1;
- }
-
- node = entry_to_node(child);
-
- for (;;) {
- unsigned offset = radix_tree_descend(node, &child, index);
- if (!child)
- goto next;
- if (!tag_get(node, iftag, offset))
- goto next;
- /* Sibling slots never have tags set on them */
- if (radix_tree_is_internal_node(child)) {
- node = entry_to_node(child);
- continue;
- }
-
- tagged++;
- node_tag_set(root, node, settag, offset);
- next:
- /* Go to next entry in node */
- index = ((index >> node->shift) + 1) << node->shift;
- /* Overflow can happen when last_index is ~0UL... */
- if (index > last_index || !index)
- break;
- offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
- while (offset == 0) {
- /*
- * We've fully scanned this node. Go up. Because
- * last_index is guaranteed to be in the tree, what
- * we do below cannot wander astray.
- */
- node = node->parent;
- offset = (index >> node->shift) & RADIX_TREE_MAP_MASK;
- }
- if (is_sibling_entry(node, node->slots[offset]))
- goto next;
- if (tagged >= nr_to_tag)
- break;
- }
-
- *first_indexp = index;
-
- return tagged;
-}
-EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
-
-/**
* radix_tree_gang_lookup - perform multiple lookup on a radix tree
* @root: radix tree root
* @results: where the results of the lookup are placed