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btrfs: delayed-ref: Use list to replace the ref_root in ref_head.

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This patch replace the rbtree used in ref_head to list.
This has the following advantage:
1) Easier merge logic.
With the new list implement, we only need to care merging the tail
ref_node with the new ref_node.
And this can be done quite easy at insert time, no need to do a
indicated merge at run_delayed_refs().

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Qu Wenruo
2015-03-30 17:03:00 +08:00
committed by Chris Mason
parent 00db646d3f
commit c6fc245499
5 changed files with 114 additions and 123 deletions
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18
fs/btrfs/delayed-ref.h
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@@ -24,9 +24,25 @@
#define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
#define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */
/*
* XXX: Qu: I really hate the design that ref_head and tree/data ref shares the
* same ref_node structure.
* Ref_head is in a higher logic level than tree/data ref, and duplicated
* bytenr/num_bytes in ref_node is really a waste or memory, they should be
* referred from ref_head.
* This gets more disgusting after we use list to store tree/data ref in
* ref_head. Must clean this mess up later.
*/
struct btrfs_delayed_ref_node {
/*
* ref_head use rb tree, stored in ref_root->href.
* indexed by bytenr
*/
struct rb_node rb_node;
/*data/tree ref use list, stored in ref_head->ref_list. */
struct list_head list;
/* the starting bytenr of the extent */
u64 bytenr;
@@ -83,7 +99,7 @@ struct btrfs_delayed_ref_head {
struct mutex mutex;
spinlock_t lock;
struct rb_root ref_root;
struct list_head ref_list;
struct rb_node href_node;