On Fri, Oct 04, 2013 at 02:55:29PM -0500, Chandra Seetharaman wrote:
> 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().
>
> While at it, this patch also changes the other usage of radix_tree_lookup() in
> alloc_extent_buffer() with find_extent_buffer() to reduce redundancy.
>
> Signed-Off-by: Chandra Seetharaman <sekha...@us.ibm.com>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index c09a40d..50345fb 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4451,6 +4451,23 @@ static void mark_extent_buffer_accessed(struct
> extent_buffer *eb)
> }
> }
>
> +struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
> + u64 start, unsigned long len)
len isn't used.
> @@ -4530,24 +4543,17 @@ 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, len);
Is it safe to do the lookup under rcu instead of under the spinlock?
The commit message should mention the difference.
- z
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