6 files changed, 173 insertions, 48 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index c4792062dd5..7114faafa9d 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -181,7 +181,8 @@ int __btrfs_cow_block(struct btrfs_trans_handle *trans,
                              struct extent_buffer *buf,
                              struct extent_buffer *parent, int parent_slot,
                              struct extent_buffer **cow_ret,
-                             u64 search_start, u64 empty_size)
+                             u64 search_start, u64 empty_size,
+                             u64 prealloc_dest)
 {
         u64 root_gen;
         struct extent_buffer *cow;
@@ -216,10 +217,27 @@ int __btrfs_cow_block(struct btrfs_trans_handle *trans,
         } else {
                 first_key.objectid = 0;
         }
-        cow = btrfs_alloc_free_block(trans, root, buf->len,
-                                     root->root_key.objectid,
-                                     root_gen, first_key.objectid, level,
-                                     search_start, empty_size);
+        if (prealloc_dest) {
+                struct btrfs_key ins;
+
+                ins.objectid = prealloc_dest;
+                ins.offset = buf->len;
+                ins.type = BTRFS_EXTENT_ITEM_KEY;
+
+                ret = btrfs_alloc_reserved_extent(trans, root,
+                                                  root->root_key.objectid,
+                                                  root_gen, level,
+                                                  first_key.objectid,
+                                                  &ins);
+                BUG_ON(ret);
+                cow = btrfs_init_new_buffer(trans, root, prealloc_dest,
+                                            buf->len);
+        } else {
+                cow = btrfs_alloc_free_block(trans, root, buf->len,
+                                             root->root_key.objectid,
+                                             root_gen, first_key.objectid,
+                                             level, search_start, empty_size);
+        }
         if (IS_ERR(cow))
                 return PTR_ERR(cow);
 
@@ -279,7 +297,7 @@ int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 int btrfs_cow_block(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root, struct extent_buffer *buf,
                     struct extent_buffer *parent, int parent_slot,
-                    struct extent_buffer **cow_ret)
+                    struct extent_buffer **cow_ret, u64 prealloc_dest)
 {
         u64 search_start;
         u64 header_trans;
@@ -302,12 +320,14 @@ int btrfs_cow_block(struct btrfs_trans_handle *trans,
             !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
                 *cow_ret = buf;
                 spin_unlock(&root->fs_info->hash_lock);
+                WARN_ON(prealloc_dest);
                 return 0;
         }
         spin_unlock(&root->fs_info->hash_lock);
         search_start = buf->start & ~((u64)(1024 * 1024 * 1024) - 1);
         ret = __btrfs_cow_block(trans, root, buf, parent,
-                                 parent_slot, cow_ret, search_start, 0);
+                                 parent_slot, cow_ret, search_start, 0,
+                                 prealloc_dest);
         return ret;
 }
 
@@ -451,7 +471,7 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans,
                 err = __btrfs_cow_block(trans, root, cur, parent, i,
                                         &cur, search_start,
                                         min(16 * blocksize,
-                                            (end_slot - i) * blocksize));
+                                            (end_slot - i) * blocksize), 0);
                 if (err) {
                         btrfs_tree_unlock(cur);
                         free_extent_buffer(cur);
@@ -803,7 +823,7 @@ static int balance_level(struct btrfs_trans_handle *trans,
                 child = read_node_slot(root, mid, 0);
                 btrfs_tree_lock(child);
                 BUG_ON(!child);
-                ret = btrfs_cow_block(trans, root, child, mid, 0, &child);
+                ret = btrfs_cow_block(trans, root, child, mid, 0, &child, 0);
                 BUG_ON(ret);
 
                 spin_lock(&root->node_lock);
@@ -836,7 +856,7 @@ static int balance_level(struct btrfs_trans_handle *trans,
         if (left) {
                 btrfs_tree_lock(left);
                 wret = btrfs_cow_block(trans, root, left,
-                                       parent, pslot - 1, &left);
+                                       parent, pslot - 1, &left, 0);
                 if (wret) {
                         ret = wret;
                         goto enospc;
@@ -846,7 +866,7 @@ static int balance_level(struct btrfs_trans_handle *trans,
         if (right) {
                 btrfs_tree_lock(right);
                 wret = btrfs_cow_block(trans, root, right,
-                                       parent, pslot + 1, &right);
+                                       parent, pslot + 1, &right, 0);
                 if (wret) {
                         ret = wret;
                         goto enospc;
@@ -1021,7 +1041,7 @@ static int noinline push_nodes_for_insert(struct btrfs_trans_handle *trans,
                         wret = 1;
                 } else {
                         ret = btrfs_cow_block(trans, root, left, parent,
-                                              pslot - 1, &left);
+                                              pslot - 1, &left, 0);
                         if (ret)
                                 wret = 1;
                         else {
@@ -1069,7 +1089,7 @@ static int noinline push_nodes_for_insert(struct btrfs_trans_handle *trans,
                 } else {
                         ret = btrfs_cow_block(trans, root, right,
                                               parent, pslot + 1,
-                                              &right);
+                                              &right, 0);
                         if (ret)
                                 wret = 1;
                         else {
@@ -1245,6 +1265,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
         u8 lowest_level = 0;
         u64 blocknr;
         u64 gen;
+        struct btrfs_key prealloc_block;
 
         lowest_level = p->lowest_level;
         WARN_ON(lowest_level && ins_len);
@@ -1253,6 +1274,9 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
                 !mutex_is_locked(&root->fs_info->alloc_mutex));
         if (ins_len < 0)
                 lowest_unlock = 2;
+
+        prealloc_block.objectid = 0;
+
 again:
         if (p->skip_locking)
                 b = btrfs_root_node(root);
@@ -1261,27 +1285,82 @@ again:
 
         while (b) {
                 level = btrfs_header_level(b);
+
+                /*
+                 * setup the path here so we can release it under lock
+                 * contention with the cow code
+                 */
+                p->nodes[level] = b;
+                if (!p->skip_locking)
+                        p->locks[level] = 1;
+
                 if (cow) {
                         int wret;
+
+                        /* is a cow on this block not required */
+                        spin_lock(&root->fs_info->hash_lock);
+                        if (btrfs_header_generation(b) == trans->transid &&
+                            !btrfs_header_flag(b, BTRFS_HEADER_FLAG_WRITTEN)) {
+                                spin_unlock(&root->fs_info->hash_lock);
+                                goto cow_done;
+                        }
+                        spin_unlock(&root->fs_info->hash_lock);
+
+                        /* ok, we have to cow, is our old prealloc the right
+                         * size?
+                         */
+                        if (prealloc_block.objectid &&
+                            prealloc_block.offset != b->len) {
+                                btrfs_free_reserved_extent(root,
+                                           prealloc_block.objectid,
+                                           prealloc_block.offset);
+                                prealloc_block.objectid = 0;
+                        }
+
+                        /*
+                         * for higher level blocks, try not to allocate blocks
+                         * with the block and the parent locks held.
+                         */
+                        if (level > 1 && !prealloc_block.objectid &&
+                            btrfs_path_lock_waiting(p, level)) {
+                                u32 size = b->len;
+                                u64 hint = b->start;
+
+                                btrfs_release_path(root, p);
+                                ret = btrfs_reserve_extent(trans, root,
+                                                           size, size, 0,
+                                                           hint, (u64)-1,
+                                                           &prealloc_block, 0);
+                                BUG_ON(ret);
+                                goto again;
+                        }
+
                         wret = btrfs_cow_block(trans, root, b,
                                                p->nodes[level + 1],
                                                p->slots[level + 1],
-                                               &b);
+                                               &b, prealloc_block.objectid);
+                        prealloc_block.objectid = 0;
                         if (wret) {
                                 free_extent_buffer(b);
-                                return wret;
+                                ret = wret;
+                                goto done;
                         }
                 }
+cow_done:
                 BUG_ON(!cow && ins_len);
                 if (level != btrfs_header_level(b))
                         WARN_ON(1);
                 level = btrfs_header_level(b);
+
                 p->nodes[level] = b;
                 if (!p->skip_locking)
                         p->locks[level] = 1;
+
                 ret = check_block(root, p, level);
-                if (ret)
-                        return -1;
+                if (ret) {
+                        ret = -1;
+                        goto done;
+                }
 
                 ret = bin_search(b, key, level, &slot);
                 if (level != 0) {
@@ -1292,15 +1371,19 @@ again:
                             BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {
                                 int sret = split_node(trans, root, p, level);
                                 BUG_ON(sret > 0);
-                                if (sret)
-                                        return sret;
+                                if (sret) {
+                                        ret = sret;
+                                        goto done;
+                                }
                                 b = p->nodes[level];
                                 slot = p->slots[level];
                         } else if (ins_len < 0) {
                                 int sret = balance_level(trans, root, p,
                                                          level);
-                                if (sret)
-                                        return sret;
+                                if (sret) {
+                                        ret = sret;
+                                        goto done;
+                                }
                                 b = p->nodes[level];
                                 if (!b) {
                                         btrfs_release_path(NULL, p);
@@ -1362,14 +1445,24 @@ again:
                                 int sret = split_leaf(trans, root, key,
                                                       p, ins_len, ret == 0);
                                 BUG_ON(sret > 0);
-                                if (sret)
-                                        return sret;
+                                if (sret) {
+                                        ret = sret;
+                                        goto done;
+                                }
                         }
                         unlock_up(p, level, lowest_unlock);
-                        return ret;
+                        goto done;
                 }
         }
-        return 1;
+        ret = 1;
+done:
+        if (prealloc_block.objectid) {
+                btrfs_free_reserved_extent(root,
+                           prealloc_block.objectid,
+                           prealloc_block.offset);
+        }
+
+        return ret;
 }
 
 /*
@@ -1840,7 +1933,7 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
 
         /* cow and double check */
         ret = btrfs_cow_block(trans, root, right, upper,
-                              slot + 1, &right);
+                              slot + 1, &right, 0);
         if (ret)
                 goto out_unlock;
 
@@ -2021,7 +2114,7 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
 
         /* cow and double check */
         ret = btrfs_cow_block(trans, root, left,
-                              path->nodes[1], slot - 1, &left);
+                              path->nodes[1], slot - 1, &left, 0);
         if (ret) {
                 /* we hit -ENOSPC, but it isn't fatal here */
                 ret = 1;
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d788ab0dcd9..9b025960bbd 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1421,6 +1421,9 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                                              int level,
                                              u64 hint,
                                              u64 empty_size);
+struct extent_buffer *btrfs_init_new_buffer(struct btrfs_trans_handle *trans,
+                                            struct btrfs_root *root,
+                                            u64 bytenr, u32 blocksize);
 int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size);
 int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root,
@@ -1451,6 +1454,7 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                       *root, u64 bytenr, u64 num_bytes,
                       u64 root_objectid, u64 ref_generation,
                       u64 owner_objectid, u64 owner_offset, int pin);
+int btrfs_free_reserved_extent(struct btrfs_root *root, u64 start, u64 len);
 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct extent_io_tree *unpin);
@@ -1484,7 +1488,7 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
 int btrfs_cow_block(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root, struct extent_buffer *buf,
                     struct extent_buffer *parent, int parent_slot,
-                    struct extent_buffer **cow_ret);
+                    struct extent_buffer **cow_ret, u64 prealloc_dest);
 int btrfs_copy_root(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct extent_buffer *buf,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 74bcd48a9c4..98a1c0faeda 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2118,6 +2118,15 @@ again:
         return 0;
 }
 
+int btrfs_free_reserved_extent(struct btrfs_root *root, u64 start, u64 len)
+{
+        maybe_lock_mutex(root);
+        set_extent_dirty(&root->fs_info->free_space_cache,
+                         start, start + len - 1, GFP_NOFS);
+        maybe_unlock_mutex(root);
+        return 0;
+}
+
 int btrfs_reserve_extent(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   u64 num_bytes, u64 min_alloc_size,
@@ -2267,6 +2276,26 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
         maybe_unlock_mutex(root);
         return ret;
 }
+
+struct extent_buffer *btrfs_init_new_buffer(struct btrfs_trans_handle *trans,
+                                            struct btrfs_root *root,
+                                            u64 bytenr, u32 blocksize)
+{
+        struct extent_buffer *buf;
+
+        buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
+        if (!buf)
+                return ERR_PTR(-ENOMEM);
+        btrfs_set_header_generation(buf, trans->transid);
+        btrfs_tree_lock(buf);
+        clean_tree_block(trans, root, buf);
+        btrfs_set_buffer_uptodate(buf);
+        set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
+                         buf->start + buf->len - 1, GFP_NOFS);
+        trans->blocks_used++;
+        return buf;
+}
+
 /*
  * helper function to allocate a block for a given tree
  * returns the tree buffer or NULL.
@@ -2293,26 +2322,8 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                 BUG_ON(ret > 0);
                 return ERR_PTR(ret);
         }
-        buf = btrfs_find_create_tree_block(root, ins.objectid, blocksize);
-        if (!buf) {
-                btrfs_free_extent(trans, root, ins.objectid, blocksize,
-                                  root->root_key.objectid, ref_generation,
-                                  0, 0, 0);
-                return ERR_PTR(-ENOMEM);
-        }
-        btrfs_set_header_generation(buf, trans->transid);
-        btrfs_tree_lock(buf);
-        clean_tree_block(trans, root, buf);
-        btrfs_set_buffer_uptodate(buf);
-
-        if (PageDirty(buf->first_page)) {
-                printk("page %lu dirty\n", buf->first_page->index);
-                WARN_ON(1);
-        }
 
-        set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
-                         buf->start + buf->len - 1, GFP_NOFS);
-        trans->blocks_used++;
+        buf = btrfs_init_new_buffer(trans, root, ins.objectid, blocksize);
         return buf;
 }
 
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index d43e14c7471..0cc314c10d6 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -56,3 +56,19 @@ int btrfs_tree_locked(struct extent_buffer *eb)
 {
         return mutex_is_locked(&eb->mutex);
 }
+
+int btrfs_path_lock_waiting(struct btrfs_path *path, int level)
+{
+        int i;
+        struct extent_buffer *eb;
+        for (i = level; i <= level + 1 && i < BTRFS_MAX_LEVEL; i++) {
+                eb = path->nodes[i];
+                if (!eb)
+                        break;
+                smp_mb();
+                if (!list_empty(&eb->mutex.wait_list))
+                        return 1;
+        }
+        return 0;
+}
+
diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h
index 2dab96d8280..bc1faef1251 100644
--- a/fs/btrfs/locking.h
+++ b/fs/btrfs/locking.h
@@ -23,4 +23,5 @@ int btrfs_tree_lock(struct extent_buffer *eb);
 int btrfs_tree_unlock(struct extent_buffer *eb);
 int btrfs_tree_locked(struct extent_buffer *eb);
 int btrfs_try_tree_lock(struct extent_buffer *eb);
+int btrfs_path_lock_waiting(struct btrfs_path *path, int level);
 #endif
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index a6877949930..9d84daf1000 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -622,7 +622,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
 
         old = btrfs_lock_root_node(root);
-        btrfs_cow_block(trans, root, old, NULL, 0, &old);
+        btrfs_cow_block(trans, root, old, NULL, 0, &old, 0);
 
         btrfs_copy_root(trans, root, old, &tmp, objectid);
         btrfs_tree_unlock(old);