[PATCH 1/2] Btrfs: remove unneeded field / smaller extent_map structure

Filipe David Borba Manana
2014-02-25T14:15:22Z

We don't need to have an unsigned int field in the extent_map struct
to tell us whether the extent map is in the inode's extent_map tree or
not. We can use the rb_node struct field and the RB_CLEAR_NODE and
RB_EMPTY_NODE macros to achieve the same task.

This reduces sizeof(struct extent_map) from 152 bytes to 144 bytes (on a
64 bits system).

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
---
fs/btrfs/extent_io.c | 2 +-
fs/btrfs/extent_map.c | 17 ++++++-----------
fs/btrfs/extent_map.h | 6 +++++-
3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index eb465e9..fd78c84 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2766,7 +2766,7 @@ __get_extent_map(struct inode *inode, struct page *page, size_t pg_offset,

if (em_cached && *em_cached) {
em = *em_cached;
- if (em->in_tree && start >= em->start &&
+ if (extent_map_in_tree(em) && start >= em->start &&
start < extent_map_end(em)) {
atomic_inc(&em->refs);
return em;
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 996ad56b..64d08f9 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -51,7 +51,7 @@ struct extent_map *alloc_extent_map(void)
em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
if (!em)
return NULL;
- em->in_tree = 0;
+ RB_CLEAR_NODE(&em->rb_node);
em->flags = 0;
em->compress_type = BTRFS_COMPRESS_NONE;
em->generation = 0;
@@ -73,7 +73,7 @@ void free_extent_map(struct extent_map *em)
return;
WARN_ON(atomic_read(&em->refs) == 0);
if (atomic_dec_and_test(&em->refs)) {
- WARN_ON(em->in_tree);
+ WARN_ON(extent_map_in_tree(em));
WARN_ON(!list_empty(&em->list));
kmem_cache_free(extent_map_cache, em);
}
@@ -99,8 +99,6 @@ static int tree_insert(struct rb_root *root, struct extent_map *em)
parent = *p;
entry = rb_entry(parent, struct extent_map, rb_node);

- WARN_ON(!entry->in_tree);
-
if (em->start < entry->start)
p = &(*p)->rb_left;
else if (em->start >= extent_map_end(entry))
@@ -128,7 +126,6 @@ static int tree_insert(struct rb_root *root, struct extent_map *em)
if (end > entry->start && em->start < extent_map_end(entry))
return -EEXIST;

- em->in_tree = 1;
rb_link_node(&em->rb_node, orig_parent, p);
rb_insert_color(&em->rb_node, root);
return 0;
@@ -153,8 +150,6 @@ static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
prev = n;
prev_entry = entry;

- WARN_ON(!entry->in_tree);
-
if (offset < entry->start)
n = n->rb_left;
else if (offset >= extent_map_end(entry))
@@ -240,12 +235,12 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
em->len += merge->len;
em->block_len += merge->block_len;
em->block_start = merge->block_start;
- merge->in_tree = 0;
em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
em->mod_start = merge->mod_start;
em->generation = max(em->generation, merge->generation);

rb_erase(&merge->rb_node, &tree->map);
+ RB_CLEAR_NODE(&merge->rb_node);
free_extent_map(merge);
}
}
@@ -257,7 +252,7 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
em->len += merge->len;
em->block_len += merge->block_len;
rb_erase(&merge->rb_node, &tree->map);
- merge->in_tree = 0;
+ RB_CLEAR_NODE(&merge->rb_node);
em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
em->generation = max(em->generation, merge->generation);
free_extent_map(merge);
@@ -319,7 +314,7 @@ out:
void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
{
clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
- if (em->in_tree)
+ if (extent_map_in_tree(em))
try_merge_map(tree, em);
}

@@ -434,6 +429,6 @@ int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
rb_erase(&em->rb_node, &tree->map);
if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
list_del_init(&em->list);
- em->in_tree = 0;
+ RB_CLEAR_NODE(&em->rb_node);
return ret;
}
diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 93fba71..f0a645a 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -33,7 +33,6 @@ struct extent_map {
unsigned long flags;
struct block_device *bdev;
atomic_t refs;
- unsigned int in_tree;
unsigned int compress_type;
struct list_head list;
};
@@ -44,6 +43,11 @@ struct extent_map_tree {
rwlock_t lock;
};

+static inline int extent_map_in_tree(const struct extent_map *em)
+{
+ return !RB_EMPTY_NODE(&em->rb_node);
+}
+
static inline u64 extent_map_end(struct extent_map *em)
{
if (em->start + em->len < em->start)
--
1.7.9.5