From: Jeff Mahoney <je...@suse.com>
For the pathlogical case, like xfstests generic/297 that creates a
large file consisting of one, repeating reflinked extent, fsck can
take hours. The root cause is that calling find_data_backref while
iterating the extent records is an O(n^2) algorithm. For my
example test run, n was 2*2^20 and fsck was at 8 hours and counting.
This patch supplements the list with an rbtree and drops the runtime
of that testcase to about 20 seconds.
Signed-off-by: Jeff Mahoney <je...@suse.com>
---
cmds-check.c | 199 ++++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 149 insertions(+), 50 deletions(-)
diff --git a/cmds-check.c b/cmds-check.c
index a202a9d..4785f00 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -77,6 +77,7 @@ static struct cache_tree *roots_info_cache = NULL;
struct extent_backref {
struct list_head list;
+ struct rb_node node;
unsigned int is_data:1;
unsigned int found_extent_tree:1;
unsigned int full_backref:1;
@@ -90,6 +91,12 @@ to_extent_backref(struct list_head *entry)
return list_entry(entry, struct extent_backref, list);
}
+static inline struct extent_backref *
+rb_node_to_extent_backref(struct rb_node *node)
+{
+ return rb_entry(node, struct extent_backref, node);
+}
+
struct data_backref {
struct extent_backref node;
union {
@@ -111,6 +118,57 @@ to_data_backref(struct extent_backref *back)
return container_of(back, struct data_backref, node);
}
+static int compare_data_backref(struct rb_node *node1,
+ struct rb_node *node2)
+{
+ struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
+ struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
+ struct data_backref *back1 = to_data_backref(ext1);
+ struct data_backref *back2 = to_data_backref(ext2);
+
+ WARN_ON(!ext1->is_data);
+ WARN_ON(!ext2->is_data);
+
+ /* parent and root are a union, so this covers both */
+ if (back1->parent > back2->parent)
+ return 1;
+ if (back1->parent < back2->parent)
+ return -1;
+
+ /* This is a full backref and the parents match. */
+ if (back1->node.full_backref)
+ return 0;
+
+ if (back1->owner > back2->owner)
+ return 1;
+ if (back1->owner < back2->owner)
+ return -1;
+
+ if (back1->offset > back2->offset)
+ return 1;
+ if (back1->offset < back2->offset)
+ return -1;
+
+ if (back1->bytes > back2->bytes)
+ return 1;
+ if (back1->bytes < back2->bytes)
+ return -1;
+
+ if (back1->found_ref && back2->found_ref) {
+ if (back1->disk_bytenr > back2->disk_bytenr)
+ return 1;
+ if (back1->disk_bytenr < back2->disk_bytenr)
+ return -1;
+
+ if (back1->found_ref > back2->found_ref)
+ return 1;
+ if (back1->found_ref < back2->found_ref)
+ return -1;
+ }
+
+ return 0;
+}
+
/*
* Much like data_backref, just removed the undetermined members
* and change it to use list_head.
@@ -140,12 +198,56 @@ to_tree_backref(struct extent_backref *back)
return container_of(back, struct tree_backref, node);
}
+static int compare_tree_backref(struct rb_node *node1,
+ struct rb_node *node2)
+{
+ struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
+ struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
+ struct tree_backref *back1 = to_tree_backref(ext1);
+ struct tree_backref *back2 = to_tree_backref(ext2);
+
+ WARN_ON(ext1->is_data);
+ WARN_ON(ext2->is_data);
+
+ /* parent and root are a union, so this covers both */
+ if (back1->parent > back2->parent)
+ return 1;
+ if (back1->parent < back2->parent)
+ return -1;
+
+ return 0;
+}
+
+static int compare_extent_backref(struct rb_node *node1,
+ struct rb_node *node2)
+{
+ struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
+ struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
+
+ if (ext1->is_data > ext2->is_data)
+ return 1;
+
+ if (ext1->is_data < ext2->is_data)
+ return -1;
+
+ if (ext1->full_backref > ext2->full_backref)
+ return 1;
+ if (ext1->full_backref < ext2->full_backref)
+ return -1;
+
+ if (ext1->is_data)
+ return compare_data_backref(node1, node2);
+ else
+ return compare_tree_backref(node1, node2);
+}
+
/* Explicit initialization for extent_record::flag_block_full_backref */
enum { FLAG_UNSET = 2 };
struct extent_record {
struct list_head backrefs;
struct list_head dups;
+ struct rb_root backref_tree;
struct list_head list;
struct cache_extent cache;
struct btrfs_disk_key parent_key;
@@ -4379,32 +4481,30 @@ static int check_block(struct btrfs_root *root,
return ret;
}
+
static struct tree_backref *find_tree_backref(struct extent_record *rec,
u64 parent, u64 root)
{
- struct list_head *cur = rec->backrefs.next;
- struct extent_backref *node;
- struct tree_backref *back;
+ struct rb_node *node;
+ struct tree_backref *back = NULL;
+ struct tree_backref match = {
+ .node = {
+ .is_data = 0,
+ },
+ };
- while(cur != &rec->backrefs) {
- node = to_extent_backref(cur);
- cur = cur->next;
- if (node->is_data)
- continue;
- back = to_tree_backref(node);
- if (parent > 0) {
- if (!node->full_backref)
- continue;
- if (parent == back->parent)
- return back;
- } else {
- if (node->full_backref)
- continue;
- if (back->root == root)
- return back;
- }
- }
- return NULL;
+ if (parent) {
+ match.parent = parent;
+ match.node.full_backref = 1;
+ } else
+ match.root = root;
+
+ node = rb_search(&rec->backref_tree, &match.node.node,
+ (rb_compare_keys)compare_extent_backref, NULL);
+ if (node)
+ back = to_tree_backref(rb_node_to_extent_backref(node));
+
+ return back;
}
static struct tree_backref *alloc_tree_backref(struct extent_record *rec,
@@ -4423,6 +4523,7 @@ static struct tree_backref *alloc_tree_backref(struct
extent_record *rec,
ref->node.full_backref = 0;
}
list_add_tail(&ref->node.list, &rec->backrefs);
+ rb_insert(&rec->backref_tree, &ref->node.node, compare_extent_backref);
return ref;
}
@@ -4433,35 +4534,31 @@ static struct data_backref *find_data_backref(struct
extent_record *rec,
int found_ref,
u64 disk_bytenr, u64 bytes)
{
- struct list_head *cur = rec->backrefs.next;
- struct extent_backref *node;
- struct data_backref *back;
+ struct rb_node *node;
+ struct data_backref *back = NULL;
+ struct data_backref match = {
+ .node = {
+ .is_data = 1,
+ },
+ .owner = owner,
+ .offset = offset,
+ .bytes = bytes,
+ .found_ref = found_ref,
+ .disk_bytenr = disk_bytenr,
+ };
- while(cur != &rec->backrefs) {
- node = to_extent_backref(cur);
- cur = cur->next;
- if (!node->is_data)
- continue;
- back = to_data_backref(node);
- if (parent > 0) {
- if (!node->full_backref)
- continue;
- if (parent == back->parent)
- return back;
- } else {
- if (node->full_backref)
- continue;
- if (back->root == root && back->owner == owner &&
- back->offset == offset) {
- if (found_ref && node->found_ref &&
- (back->bytes != bytes ||
- back->disk_bytenr != disk_bytenr))
- continue;
- return back;
- }
- }
- }
- return NULL;
+ if (parent) {
+ match.parent = parent;
+ match.node.full_backref = 1;
+ } else
+ match.root = root;
+
+ node = rb_search(&rec->backref_tree, &match.node.node,
+ (rb_compare_keys)compare_extent_backref, NULL);
+ if (node)
+ back = to_data_backref(rb_node_to_extent_backref(node));
+
+ return back;
}
static struct data_backref *alloc_data_backref(struct extent_record *rec,
@@ -4491,6 +4588,7 @@ static struct data_backref *alloc_data_backref(struct
extent_record *rec,
ref->found_ref = 0;
ref->num_refs = 0;
list_add_tail(&ref->node.list, &rec->backrefs);
+ rb_insert(&rec->backref_tree, &ref->node.node, compare_extent_backref);
if (max_size > rec->max_size)
rec->max_size = max_size;
return ref;
@@ -4578,6 +4676,7 @@ static int add_extent_rec_nolookup(struct cache_tree
*extent_cache,
INIT_LIST_HEAD(&rec->backrefs);
INIT_LIST_HEAD(&rec->dups);
INIT_LIST_HEAD(&rec->list);
+ rec->backref_tree = RB_ROOT;
memcpy(&rec->parent_key, &tmpl->parent_key, sizeof(tmpl->parent_key));
rec->cache.start = tmpl->start;
rec->cache.size = tmpl->nr;
--
2.7.1
--
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