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: 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>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b0ea9f4..ebc784a 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -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;
 }
 

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c10291c..5439f24 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -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 =

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index f98602e..19620c5 100644 (file)
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -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