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Commit 452c75c3 authored by Chandra Seetharaman's avatar Chandra Seetharaman Committed by Chris Mason
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Btrfs: Simplify the logic in alloc_extent_buffer() for existing extent buffer case 



alloc_extent_buffer() uses radix_tree_lookup() when radix_tree_insert()
fails with EEXIST. That part of the code is very similar to the code in
find_extent_buffer(). This patch replaces radix_tree_lookup() and
surrounding code in alloc_extent_buffer() with find_extent_buffer().

Note that radix_tree_lookup() does not need to be protected by
tree->buffer_lock. It is protected by eb->refs.

While at it, this patch
  - changes the other usage of radix_tree_lookup() in alloc_extent_buffer()
    with find_extent_buffer() to reduce redundancy.
  - removes the unused argument 'len' to find_extent_buffer().

Signed-Off-by: default avatarChandra Seetharaman <sekharan@us.ibm.com>
Reviewed-by: default avatarZach Brown <zab@redhat.com>

Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent 7f4ca37c

fs/btrfs/disk-io.c

+1 −2
Original line number Diff line number Diff line
@@ -1104,8 +1104,7 @@ struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root, 
{

	struct inode *btree_inode = root->fs_info->btree_inode;

	struct extent_buffer *eb;

	eb = find_extent_buffer(&BTRFS_I(btree_inode)->io_tree,

				bytenr, blocksize);

	eb = find_extent_buffer(&BTRFS_I(btree_inode)->io_tree, bytenr);

	return eb;

}

fs/btrfs/extent_io.c

+26 −37
Original line number Diff line number Diff line
@@ -4486,6 +4486,23 @@ static void mark_extent_buffer_accessed(struct extent_buffer *eb) 
	}

}



struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,

					 		u64 start)

{

	struct extent_buffer *eb;



	rcu_read_lock();

	eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);

	if (eb && atomic_inc_not_zero(&eb->refs)) {

		rcu_read_unlock();

		mark_extent_buffer_accessed(eb);

		return eb;

	}

	rcu_read_unlock();



	return NULL;

}



struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,

					  u64 start, unsigned long len)

{
@@ -4499,14 +4516,10 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, 
	int uptodate = 1;

	int ret;



	rcu_read_lock();

	eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);

	if (eb && atomic_inc_not_zero(&eb->refs)) {

		rcu_read_unlock();

		mark_extent_buffer_accessed(eb);



	eb = find_extent_buffer(tree, start);

	if (eb)

		return eb;

	}

	rcu_read_unlock();



	eb = __alloc_extent_buffer(tree, start, len, GFP_NOFS);

	if (!eb)
@@ -4565,24 +4578,17 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, 


	spin_lock(&tree->buffer_lock);

	ret = radix_tree_insert(&tree->buffer, start >> PAGE_CACHE_SHIFT, eb);

	if (ret == -EEXIST) {

		exists = radix_tree_lookup(&tree->buffer,

						start >> PAGE_CACHE_SHIFT);

		if (!atomic_inc_not_zero(&exists->refs)) {

			spin_unlock(&tree->buffer_lock);

			radix_tree_preload_end();

			exists = NULL;

			goto again;

		}

	spin_unlock(&tree->buffer_lock);

	radix_tree_preload_end();

		mark_extent_buffer_accessed(exists);

	if (ret == -EEXIST) {

		exists = find_extent_buffer(tree, start);

		if (exists)

			goto free_eb;

		else

			goto again;

	}

	/* add one reference for the tree */

	check_buffer_tree_ref(eb);

	spin_unlock(&tree->buffer_lock);

	radix_tree_preload_end();



	/*

	 * there is a race where release page may have
@@ -4613,23 +4619,6 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, 
	return exists;

}



struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,

					 u64 start, unsigned long len)

{

	struct extent_buffer *eb;



	rcu_read_lock();

	eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);

	if (eb && atomic_inc_not_zero(&eb->refs)) {

		rcu_read_unlock();

		mark_extent_buffer_accessed(eb);

		return eb;

	}

	rcu_read_unlock();



	return NULL;

}



static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)

{

	struct extent_buffer *eb =

fs/btrfs/extent_io.h

+1 −1
Original line number Diff line number Diff line
@@ -271,7 +271,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, 
struct extent_buffer *alloc_dummy_extent_buffer(u64 start, unsigned long len);

struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src);

struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,

					 u64 start, unsigned long len);

					 u64 start);

void free_extent_buffer(struct extent_buffer *eb);

void free_extent_buffer_stale(struct extent_buffer *eb);

#define WAIT_NONE	0