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Btrfs: preftree: use rb_first_cached 

rb_first_cached() trades an extra pointer "leftmost" for doing the same
job as rb_first() but in O(1).

While resolving indirect refs and missing refs, it always looks for the
first rb entry in a while loop, it's helpful to use rb_first_cached
instead.

For more details about the optimization see patch "Btrfs: delayed-refs:
use rb_first_cached for href_root".

Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
hifive-unleashed-5.1
Liu Bo 2018-08-23 03:51:53 +08:00 committed by David Sterba
parent 07e1ce096d
commit ecf160b424
1 changed files with 17 additions and 15 deletions
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32
fs/btrfs/backref.c
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@ -112,11 +112,11 @@ static int find_extent_in_eb(const struct extent_buffer *eb,
}
struct preftree {
struct rb_root root;
struct rb_root_cached root;
unsigned int count;
};
#define PREFTREE_INIT { .root = RB_ROOT, .count = 0 }
#define PREFTREE_INIT { .root = RB_ROOT_CACHED, .count = 0 }
struct preftrees {
struct preftree direct; /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
@ -225,14 +225,15 @@ static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
struct prelim_ref *newref,
struct share_check *sc)
{
struct rb_root *root;
struct rb_root_cached *root;
struct rb_node **p;
struct rb_node *parent = NULL;
struct prelim_ref *ref;
int result;
bool leftmost = true;
root = &preftree->root;
p = &root->rb_node;
p = &root->rb_root.rb_node;
while (*p) {
parent = *p;
@ -242,6 +243,7 @@ static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
p = &(*p)->rb_left;
} else if (result > 0) {
p = &(*p)->rb_right;
leftmost = false;
} else {
/* Identical refs, merge them and free @newref */
struct extent_inode_elem *eie = ref->inode_list;
@ -272,7 +274,7 @@ static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
preftree->count++;
trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count);
rb_link_node(&newref->rbnode, parent, p);
rb_insert_color(&newref->rbnode, root);
rb_insert_color_cached(&newref->rbnode, root, leftmost);
}
/*
@ -283,11 +285,11 @@ static void prelim_release(struct preftree *preftree)
{
struct prelim_ref *ref, *next_ref;
rbtree_postorder_for_each_entry_safe(ref, next_ref, &preftree->root,
rbnode)
rbtree_postorder_for_each_entry_safe(ref, next_ref,
&preftree->root.rb_root, rbnode)
free_pref(ref);
preftree->root = RB_ROOT;
preftree->root = RB_ROOT_CACHED;
preftree->count = 0;
}
@ -627,7 +629,7 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
* freeing the entire indirect tree when we're done. In some test
* cases, the tree can grow quite large (~200k objects).
*/
while ((rnode = rb_first(&preftrees->indirect.root))) {
while ((rnode = rb_first_cached(&preftrees->indirect.root))) {
struct prelim_ref *ref;
ref = rb_entry(rnode, struct prelim_ref, rbnode);
@ -637,7 +639,7 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
goto out;
}
rb_erase(&ref->rbnode, &preftrees->indirect.root);
rb_erase_cached(&ref->rbnode, &preftrees->indirect.root);
preftrees->indirect.count--;
if (ref->count == 0) {
@ -717,9 +719,9 @@ static int add_missing_keys(struct btrfs_fs_info *fs_info,
struct preftree *tree = &preftrees->indirect_missing_keys;
struct rb_node *node;
while ((node = rb_first(&tree->root))) {
while ((node = rb_first_cached(&tree->root))) {
ref = rb_entry(node, struct prelim_ref, rbnode);
rb_erase(node, &tree->root);
rb_erase_cached(node, &tree->root);
BUG_ON(ref->parent); /* should not be a direct ref */
BUG_ON(ref->key_for_search.type);
@ -1229,14 +1231,14 @@ again:
if (ret)
goto out;
WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root));
WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root.rb_root));
ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees,
extent_item_pos, total_refs, sc, ignore_offset);
if (ret)
goto out;
WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root));
WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root.rb_root));
/*
* This walks the tree of merged and resolved refs. Tree blocks are
@ -1245,7 +1247,7 @@ again:
*
* We release the entire tree in one go before returning.
*/
node = rb_first(&preftrees.direct.root);
node = rb_first_cached(&preftrees.direct.root);
while (node) {
ref = rb_entry(node, struct prelim_ref, rbnode);
node = rb_next(&ref->rbnode);