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Btrfs: Simplify the logic in alloc_extent_buffer() for existing extent buffer case

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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: Chandra Seetharaman <sekharan@us.ibm.com>
Reviewed-by: Zach Brown <zab@redhat.com>

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Chandra Seetharaman 2013-10-07 10:45:25 -05:00 committed by Chris Mason
parent 7f4ca37c48
commit 452c75c3d2
3 changed files with 28 additions and 40 deletions
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3
fs/btrfs/disk-io.c
View file

@ -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;
}

63
fs/btrfs/extent_io.c
View file

@ -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 @@ again:
spin_lock(&tree->buffer_lock);
ret = radix_tree_insert(&tree->buffer, start >> PAGE_CACHE_SHIFT, eb);
spin_unlock(&tree->buffer_lock);
radix_tree_preload_end();
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;
exists = find_extent_buffer(tree, start);
if (exists)
goto free_eb;
else
goto again;
}
spin_unlock(&tree->buffer_lock);
radix_tree_preload_end();
mark_extent_buffer_accessed(exists);
goto free_eb;
}
/* 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 @@ free_eb:
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 =

2
fs/btrfs/extent_io.h
View file

@ -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