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Commit 27a3507d authored by Filipe Manana's avatar Filipe Manana Committed by Chris Mason
Browse files

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: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 6f84e236

fs/btrfs/extent_io.c

+20 −17
Original line number Diff line number Diff line
@@ -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 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, 
			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 @@ __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, 
	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 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, 
	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

fs/btrfs/extent_io.h

+0 −1
Original line number Diff line number Diff line
@@ -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;