1 files changed, 297 insertions, 0 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index df19b60eef61..3fdadd28e935 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -18,6 +18,15 @@
 
 #include <linux/sched.h>
 #include "ctree.h"
+#include "free-space-cache.h"
+#include "transaction.h"
+
+struct btrfs_free_space {
+        struct rb_node bytes_index;
+        struct rb_node offset_index;
+        u64 offset;
+        u64 bytes;
+};
 
 static int tree_insert_offset(struct rb_root *root, u64 offset,
                               struct rb_node *node)
@@ -371,12 +380,58 @@ u64 btrfs_block_group_free_space(struct btrfs_block_group_cache *block_group)
         return ret;
 }
 
+/*
+ * for a given cluster, put all of its extents back into the free
+ * space cache.  If the block group passed doesn't match the block group
+ * pointed to by the cluster, someone else raced in and freed the
+ * cluster already.  In that case, we just return without changing anything
+ */
+static int
+__btrfs_return_cluster_to_free_space(
+                             struct btrfs_block_group_cache *block_group,
+                             struct btrfs_free_cluster *cluster)
+{
+        struct btrfs_free_space *entry;
+        struct rb_node *node;
+
+        spin_lock(&cluster->lock);
+        if (cluster->block_group != block_group)
+                goto out;
+
+        cluster->window_start = 0;
+        node = rb_first(&cluster->root);
+        while(node) {
+                entry = rb_entry(node, struct btrfs_free_space, offset_index);
+                node = rb_next(&entry->offset_index);
+                rb_erase(&entry->offset_index, &cluster->root);
+                link_free_space(block_group, entry);
+        }
+        list_del_init(&cluster->block_group_list);
+
+        btrfs_put_block_group(cluster->block_group);
+        cluster->block_group = NULL;
+        cluster->root.rb_node = NULL;
+out:
+        spin_unlock(&cluster->lock);
+        return 0;
+}
+
 void btrfs_remove_free_space_cache(struct btrfs_block_group_cache *block_group)
 {
         struct btrfs_free_space *info;
         struct rb_node *node;
+        struct btrfs_free_cluster *cluster;
+        struct btrfs_free_cluster *safe;
 
         spin_lock(&block_group->tree_lock);
+
+        list_for_each_entry_safe(cluster, safe, &block_group->cluster_list,
+                                 block_group_list) {
+
+                WARN_ON(cluster->block_group != block_group);
+                __btrfs_return_cluster_to_free_space(block_group, cluster);
+        }
+
         while ((node = rb_last(&block_group->free_space_bytes)) != NULL) {
                 info = rb_entry(node, struct btrfs_free_space, bytes_index);
                 unlink_free_space(block_group, info);
@@ -417,3 +472,245 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group_cache *block_group,
 
         return ret;
 }
+
+/*
+ * given a cluster, put all of its extents back into the free space
+ * cache.  If a block group is passed, this function will only free
+ * a cluster that belongs to the passed block group.
+ *
+ * Otherwise, it'll get a reference on the block group pointed to by the
+ * cluster and remove the cluster from it.
+ */
+int btrfs_return_cluster_to_free_space(
+                               struct btrfs_block_group_cache *block_group,
+                               struct btrfs_free_cluster *cluster)
+{
+        int ret;
+
+        /* first, get a safe pointer to the block group */
+        spin_lock(&cluster->lock);
+        if (!block_group) {
+                block_group = cluster->block_group;
+                if (!block_group) {
+                        spin_unlock(&cluster->lock);
+                        return 0;
+                }
+        } else if (cluster->block_group != block_group) {
+                /* someone else has already freed it don't redo their work */
+                spin_unlock(&cluster->lock);
+                return 0;
+        }
+        atomic_inc(&block_group->count);
+        spin_unlock(&cluster->lock);
+
+        /* now return any extents the cluster had on it */
+        spin_lock(&block_group->tree_lock);
+        ret = __btrfs_return_cluster_to_free_space(block_group, cluster);
+        spin_unlock(&block_group->tree_lock);
+
+        /* finally drop our ref */
+        btrfs_put_block_group(block_group);
+        return ret;
+}
+
+/*
+ * given a cluster, try to allocate 'bytes' from it, returns 0
+ * if it couldn't find anything suitably large, or a logical disk offset
+ * if things worked out
+ */
+u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
+                             struct btrfs_free_cluster *cluster, u64 bytes,
+                             u64 min_start)
+{
+        struct btrfs_free_space *entry = NULL;
+        struct rb_node *node;
+        u64 ret = 0;
+
+        spin_lock(&cluster->lock);
+        if (bytes > cluster->max_size)
+                goto out;
+
+        if (cluster->block_group != block_group)
+                goto out;
+
+        node = rb_first(&cluster->root);
+        if (!node)
+                goto out;
+
+        entry = rb_entry(node, struct btrfs_free_space, offset_index);
+
+        while(1) {
+                if (entry->bytes < bytes || entry->offset < min_start) {
+                        struct rb_node *node;
+
+                        node = rb_next(&entry->offset_index);
+                        if (!node)
+                                break;
+                        entry = rb_entry(node, struct btrfs_free_space,
+                                         offset_index);
+                        continue;
+                }
+                ret = entry->offset;
+
+                entry->offset += bytes;
+                entry->bytes -= bytes;
+
+                if (entry->bytes == 0) {
+                        rb_erase(&entry->offset_index, &cluster->root);
+                        kfree(entry);
+                }
+                break;
+        }
+out:
+        spin_unlock(&cluster->lock);
+        return ret;
+}
+
+/*
+ * here we try to find a cluster of blocks in a block group.  The goal
+ * is to find at least bytes free and up to empty_size + bytes free.
+ * We might not find them all in one contiguous area.
+ *
+ * returns zero and sets up cluster if things worked out, otherwise
+ * it returns -enospc
+ */
+int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
+                             struct btrfs_block_group_cache *block_group,
+                             struct btrfs_free_cluster *cluster,
+                             u64 offset, u64 bytes, u64 empty_size)
+{
+        struct btrfs_free_space *entry = NULL;
+        struct rb_node *node;
+        struct btrfs_free_space *next;
+        struct btrfs_free_space *last;
+        u64 min_bytes;
+        u64 window_start;
+        u64 window_free;
+        u64 max_extent = 0;
+        int total_retries = 0;
+        int ret;
+
+        /* for metadata, allow allocates with more holes */
+        if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
+                /*
+                 * we want to do larger allocations when we are
+                 * flushing out the delayed refs, it helps prevent
+                 * making more work as we go along.
+                 */
+                if (trans->transaction->delayed_refs.flushing)
+                        min_bytes = max(bytes, (bytes + empty_size) >> 1);
+                else
+                        min_bytes = max(bytes, (bytes + empty_size) >> 4);
+        } else
+                min_bytes = max(bytes, (bytes + empty_size) >> 2);
+
+        spin_lock(&block_group->tree_lock);
+        spin_lock(&cluster->lock);
+
+        /* someone already found a cluster, hooray */
+        if (cluster->block_group) {
+                ret = 0;
+                goto out;
+        }
+again:
+        min_bytes = min(min_bytes, bytes + empty_size);
+        entry = tree_search_bytes(&block_group->free_space_bytes,
+                                  offset, min_bytes);
+        if (!entry) {
+                ret = -ENOSPC;
+                goto out;
+        }
+        window_start = entry->offset;
+        window_free = entry->bytes;
+        last = entry;
+        max_extent = entry->bytes;
+
+        while(1) {
+                /* out window is just right, lets fill it */
+                if (window_free >= bytes + empty_size)
+                        break;
+
+                node = rb_next(&last->offset_index);
+                if (!node) {
+                        ret = -ENOSPC;
+                        goto out;
+                }
+                next = rb_entry(node, struct btrfs_free_space, offset_index);
+
+                /*
+                 * we haven't filled the empty size and the window is
+                 * very large.  reset and try again
+                 */
+                if (next->offset - window_start > (bytes + empty_size) * 2) {
+                        entry = next;
+                        window_start = entry->offset;
+                        window_free = entry->bytes;
+                        last = entry;
+                        max_extent = 0;
+                        total_retries++;
+                        if (total_retries % 256 == 0) {
+                                if (min_bytes >= (bytes + empty_size)) {
+                                        ret = -ENOSPC;
+                                        goto out;
+                                }
+                                /*
+                                 * grow our allocation a bit, we're not having
+                                 * much luck
+                                 */
+                                min_bytes *= 2;
+                                goto again;
+                        }
+                } else {
+                        last = next;
+                        window_free += next->bytes;
+                        if (entry->bytes > max_extent)
+                                max_extent = entry->bytes;
+                }
+        }
+
+        cluster->window_start = entry->offset;
+
+        /*
+         * now we've found our entries, pull them out of the free space
+         * cache and put them into the cluster rbtree
+         *
+         * The cluster includes an rbtree, but only uses the offset index
+         * of each free space cache entry.
+         */
+        while(1) {
+                node = rb_next(&entry->offset_index);
+                unlink_free_space(block_group, entry);
+                ret = tree_insert_offset(&cluster->root, entry->offset,
+                                         &entry->offset_index);
+                BUG_ON(ret);
+
+                if (!node || entry == last)
+                        break;
+
+                entry = rb_entry(node, struct btrfs_free_space, offset_index);
+        }
+        ret = 0;
+        cluster->max_size = max_extent;
+        atomic_inc(&block_group->count);
+        list_add_tail(&cluster->block_group_list, &block_group->cluster_list);
+        cluster->block_group = block_group;
+out:
+        spin_unlock(&cluster->lock);
+        spin_unlock(&block_group->tree_lock);
+
+        return ret;
+}
+
+/*
+ * simple code to zero out a cluster
+ */
+void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
+{
+        spin_lock_init(&cluster->lock);
+        spin_lock_init(&cluster->refill_lock);
+        cluster->root.rb_node = NULL;
+        cluster->max_size = 0;
+        INIT_LIST_HEAD(&cluster->block_group_list);
+        cluster->block_group = NULL;
+}
+