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Btrfs: reduce size of struct extent_state

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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>
This commit is contained in:
Filipe Manana 2014-07-06 20:09:59 +01:00 committed by Chris Mason
parent 6f84e23646
commit 27a3507de9
2 changed files with 20 additions and 18 deletions
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37
fs/btrfs/extent_io.c
View file

@ -25,6 +25,11 @@ static struct kmem_cache *extent_state_cache;
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 @@ void btrfs_leak_debug_check(void)
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 @@ static struct extent_state *alloc_extent_state(gfp_t mask)
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 @@ void free_extent_state(struct extent_state *state)
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 @@ static void merge_state(struct extent_io_tree *tree,
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 @@ static void merge_state(struct extent_io_tree *tree,
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 @@ static int insert_state(struct extent_io_tree *tree,
found->start, found->end, start, end);
return -EEXIST;
}
state->tree = tree;
merge_state(tree, state);
return 0;
}
@ -486,7 +490,6 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
free_extent_state(prealloc);
return -EEXIST;
}
prealloc->tree = tree;
return 0;
}
@ -524,9 +527,9 @@ static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
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 @@ again:
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 @@ again:
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 @@ again:
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 @@ int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
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 test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
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

1
fs/btrfs/extent_io.h
View file

@ -108,7 +108,6 @@ struct extent_state {
struct rb_node rb_node;
/* ADD NEW ELEMENTS AFTER THIS */
struct extent_io_tree *tree;
wait_queue_head_t wq;
atomic_t refs;
unsigned long state;