From 709c0486b9fe9586736b108b7233bbce0300cfa5 Mon Sep 17 00:00:00 2001 From: Arne Jansen Date: Mon, 12 Sep 2011 12:22:57 +0200 Subject: [PATCH] Btrfs: Test code to change the order of delayed-ref processing Normally delayed refs get processed in ascending bytenr order. This correlates in most cases to the order added. To expose dependencies on this order, we start to process the tree in the middle instead of the beginning. This code is only effective when SCRAMBLE_DELAYED_REFS is defined. Signed-off-by: Arne Jansen --- fs/btrfs/extent-tree.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 94ce79f76e5f..b13f1fbc3733 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -34,6 +34,8 @@ #include "locking.h" #include "free-space-cache.h" +#undef SCRAMBLE_DELAYED_REFS + /* * control flags for do_chunk_alloc's force field * CHUNK_ALLOC_NO_FORCE means to only allocate a chunk @@ -2364,6 +2366,49 @@ static void wait_for_more_refs(struct btrfs_fs_info *fs_info, spin_lock(&delayed_refs->lock); } +#ifdef SCRAMBLE_DELAYED_REFS +/* + * Normally delayed refs get processed in ascending bytenr order. This + * correlates in most cases to the order added. To expose dependencies on this + * order, we start to process the tree in the middle instead of the beginning + */ +static u64 find_middle(struct rb_root *root) +{ + struct rb_node *n = root->rb_node; + struct btrfs_delayed_ref_node *entry; + int alt = 1; + u64 middle; + u64 first = 0, last = 0; + + n = rb_first(root); + if (n) { + entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node); + first = entry->bytenr; + } + n = rb_last(root); + if (n) { + entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node); + last = entry->bytenr; + } + n = root->rb_node; + + while (n) { + entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node); + WARN_ON(!entry->in_tree); + + middle = entry->bytenr; + + if (alt) + n = n->rb_left; + else + n = n->rb_right; + + alt = 1 - alt; + } + return middle; +} +#endif + /* * this starts processing the delayed reference count updates and * extent insertions we have queued up so far. count can be @@ -2406,6 +2451,10 @@ again: consider_waiting = 0; spin_lock(&delayed_refs->lock); +#ifdef SCRAMBLE_DELAYED_REFS + delayed_refs->run_delayed_start = find_middle(&delayed_refs->root); +#endif + if (count == 0) { count = delayed_refs->num_entries * 2; run_most = 1; -- 2.11.0