Btrfs: reduce size of struct extent_state
The tree field of struct extent_state was only used to figure out if
an extent state was connected to an inode's io tree or not. For this
we can just use the rb_node field itself.
On a x86_64 system with this change the sizeof(struct extent_state) is
reduced from 96 bytes down to 88 bytes, meaning that with a page size
of 4096 bytes we can now store 46 extent states per page instead of 42.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1009fa8..816e80e 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -25,6 +25,11 @@
static struct kmem_cache *extent_buffer_cache;
static struct bio_set *btrfs_bioset;
+static inline bool extent_state_in_tree(const struct extent_state *state)
+{
+ return !RB_EMPTY_NODE(&state->rb_node);
+}
+
#ifdef CONFIG_BTRFS_DEBUG
static LIST_HEAD(buffers);
static LIST_HEAD(states);
@@ -59,9 +64,9 @@
while (!list_empty(&states)) {
state = list_entry(states.next, struct extent_state, leak_list);
- printk(KERN_ERR "BTRFS: state leak: start %llu end %llu "
- "state %lu in tree %p refs %d\n",
- state->start, state->end, state->state, state->tree,
+ pr_err("BTRFS: state leak: start %llu end %llu state %lu in tree %d refs %d\n",
+ state->start, state->end, state->state,
+ extent_state_in_tree(state),
atomic_read(&state->refs));
list_del(&state->leak_list);
kmem_cache_free(extent_state_cache, state);
@@ -209,7 +214,7 @@
return state;
state->state = 0;
state->private = 0;
- state->tree = NULL;
+ RB_CLEAR_NODE(&state->rb_node);
btrfs_leak_debug_add(&state->leak_list, &states);
atomic_set(&state->refs, 1);
init_waitqueue_head(&state->wq);
@@ -222,7 +227,7 @@
if (!state)
return;
if (atomic_dec_and_test(&state->refs)) {
- WARN_ON(state->tree);
+ WARN_ON(extent_state_in_tree(state));
btrfs_leak_debug_del(&state->leak_list);
trace_free_extent_state(state, _RET_IP_);
kmem_cache_free(extent_state_cache, state);
@@ -371,8 +376,8 @@
other->state == state->state) {
merge_cb(tree, state, other);
state->start = other->start;
- other->tree = NULL;
rb_erase(&other->rb_node, &tree->state);
+ RB_CLEAR_NODE(&other->rb_node);
free_extent_state(other);
}
}
@@ -383,8 +388,8 @@
other->state == state->state) {
merge_cb(tree, state, other);
state->end = other->end;
- other->tree = NULL;
rb_erase(&other->rb_node, &tree->state);
+ RB_CLEAR_NODE(&other->rb_node);
free_extent_state(other);
}
}
@@ -442,7 +447,6 @@
found->start, found->end, start, end);
return -EEXIST;
}
- state->tree = tree;
merge_state(tree, state);
return 0;
}
@@ -486,7 +490,6 @@
free_extent_state(prealloc);
return -EEXIST;
}
- prealloc->tree = tree;
return 0;
}
@@ -524,9 +527,9 @@
wake_up(&state->wq);
if (state->state == 0) {
next = next_state(state);
- if (state->tree) {
+ if (extent_state_in_tree(state)) {
rb_erase(&state->rb_node, &tree->state);
- state->tree = NULL;
+ RB_CLEAR_NODE(&state->rb_node);
free_extent_state(state);
} else {
WARN_ON(1);
@@ -606,8 +609,8 @@
cached_state = NULL;
}
- if (cached && cached->tree && cached->start <= start &&
- cached->end > start) {
+ if (cached && extent_state_in_tree(cached) &&
+ cached->start <= start && cached->end > start) {
if (clear)
atomic_dec(&cached->refs);
state = cached;
@@ -843,7 +846,7 @@
if (cached_state && *cached_state) {
state = *cached_state;
if (state->start <= start && state->end > start &&
- state->tree) {
+ extent_state_in_tree(state)) {
node = &state->rb_node;
goto hit_next;
}
@@ -1069,7 +1072,7 @@
if (cached_state && *cached_state) {
state = *cached_state;
if (state->start <= start && state->end > start &&
- state->tree) {
+ extent_state_in_tree(state)) {
node = &state->rb_node;
goto hit_next;
}
@@ -1459,7 +1462,7 @@
spin_lock(&tree->lock);
if (cached_state && *cached_state) {
state = *cached_state;
- if (state->end == start - 1 && state->tree) {
+ if (state->end == start - 1 && extent_state_in_tree(state)) {
n = rb_next(&state->rb_node);
while (n) {
state = rb_entry(n, struct extent_state,
@@ -1905,7 +1908,7 @@
int bitset = 0;
spin_lock(&tree->lock);
- if (cached && cached->tree && cached->start <= start &&
+ if (cached && extent_state_in_tree(cached) && cached->start <= start &&
cached->end > start)
node = &cached->rb_node;
else