4 files changed, 38 insertions, 39 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index dff4da082d06..1b756fae2799 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -63,7 +63,6 @@ void btrfs_free_path(struct btrfs_path *p)
 void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
 {
         int i;
-        int skip = p->skip_locking;
         int keep = p->keep_locks;
 
         for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
@@ -76,7 +75,6 @@ void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
                 free_extent_buffer(p->nodes[i]);
         }
         memset(p, 0, sizeof(*p));
-        p->skip_locking = skip;
         p->keep_locks = keep;
 }
 
@@ -1137,7 +1135,6 @@ static void reada_for_search(struct btrfs_root *root, struct btrfs_path *path,
                 return;
 
         node = path->nodes[level];
-        WARN_ON(!path->skip_locking && !btrfs_tree_locked(node));
 
         search = btrfs_node_blockptr(node, slot);
         blocksize = btrfs_level_size(root, level - 1);
@@ -1192,6 +1189,7 @@ static void unlock_up(struct btrfs_path *path, int level, int lowest_unlock)
 {
         int i;
         int skip_level = level;
+        int no_skips = 0;
         struct extent_buffer *t;
 
         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
@@ -1199,27 +1197,24 @@ static void unlock_up(struct btrfs_path *path, int level, int lowest_unlock)
                         break;
                 if (!path->locks[i])
                         break;
-                if (path->slots[i] == 0) {
+                if (!no_skips && path->slots[i] == 0) {
                         skip_level = i + 1;
                         continue;
                 }
-                if (path->keep_locks) {
+                if (!no_skips && path->keep_locks) {
                         u32 nritems;
                         t = path->nodes[i];
                         nritems = btrfs_header_nritems(t);
-                        if (nritems < 2 || path->slots[i] >= nritems - 2) {
-if (path->keep_locks) {
-//printk("path %p skip level now %d\n", path, skip_level);
-}
+                        if (nritems < 1 || path->slots[i] >= nritems - 1) {
                                 skip_level = i + 1;
                                 continue;
                         }
                 }
+                if (skip_level < i && i >= lowest_unlock)
+                        no_skips = 1;
+
                 t = path->nodes[i];
                 if (i >= lowest_unlock && i > skip_level && path->locks[i]) {
-if (path->keep_locks) {
-//printk("path %p unlocking level %d slot %d nritems %d skip_level %d\n", path, i, path->slots[i], btrfs_header_nritems(t), skip_level);
-}
                         btrfs_tree_unlock(t);
                         path->locks[i] = 0;
                 }
@@ -1244,6 +1239,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
                       ins_len, int cow)
 {
         struct extent_buffer *b;
+        struct extent_buffer *tmp;
         int slot;
         int ret;
         int level;
@@ -1263,10 +1259,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
         if (ins_len < 0)
                 lowest_unlock = 2;
 again:
-        if (!p->skip_locking)
-                b = btrfs_lock_root_node(root);
-        else
-                b = btrfs_root_node(root);
+        b = btrfs_lock_root_node(root);
 
         while (b) {
                 level = btrfs_header_level(b);
@@ -1286,8 +1279,7 @@ again:
                         WARN_ON(1);
                 level = btrfs_header_level(b);
                 p->nodes[level] = b;
-                if (!p->skip_locking)
-                        p->locks[level] = 1;
+                p->locks[level] = 1;
                 ret = check_block(root, p, level);
                 if (ret)
                         return -1;
@@ -1328,10 +1320,29 @@ again:
                                 reada_for_search(root, p, level, slot,
                                                  key->objectid);
 
-                        b = read_node_slot(root, b, slot);
-                        if (!p->skip_locking)
-                                btrfs_tree_lock(b);
-                        unlock_up(p, level + 1, lowest_unlock);
+                        tmp = btrfs_find_tree_block(root,
+                                          btrfs_node_blockptr(b, slot),
+                                          btrfs_level_size(root, level - 1));
+                        if (tmp && btrfs_buffer_uptodate(tmp,
+                                   btrfs_node_ptr_generation(b, slot))) {
+                                b = tmp;
+                        } else {
+                                /*
+                                 * reduce lock contention at high levels
+                                 * of the btree by dropping locks before
+                                 * we read.
+                                 */
+                                if (level > 1) {
+                                        btrfs_release_path(NULL, p);
+                                        if (tmp)
+                                                free_extent_buffer(tmp);
+                                        goto again;
+                                } else {
+                                        b = read_node_slot(root, b, slot);
+                                }
+                        }
+                        btrfs_tree_lock(b);
+                        unlock_up(p, level, lowest_unlock);
                 } else {
                         p->slots[level] = slot;
                         if (ins_len > 0 && btrfs_leaf_free_space(root, b) <
@@ -3007,17 +3018,8 @@ int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
                         reada_for_search(root, path, level, slot, 0);
 
                 next = read_node_slot(root, c, slot);
-                if (!path->skip_locking) {
-                        if (!btrfs_tree_locked(c)) {
-                                int i;
-                                WARN_ON(1);
-printk("path %p no lock on level %d\n", path, level);
-for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
-printk("path %p level %d slot %d nritems %d\n", path, i, path->slots[i], btrfs_header_nritems(path->nodes[i]));
-}
-                        }
-                        btrfs_tree_lock(next);
-                }
+                WARN_ON(!btrfs_tree_locked(c));
+                btrfs_tree_lock(next);
                 break;
         }
         path->slots[level] = slot;
@@ -3035,10 +3037,8 @@ printk("path %p level %d slot %d nritems %d\n", path, i, path->slots[i], btrfs_h
                 if (level == 1 && path->locks[1] && path->reada)
                         reada_for_search(root, path, level, slot, 0);
                 next = read_node_slot(root, next, 0);
-                if (!path->skip_locking) {
-                        WARN_ON(!btrfs_tree_locked(path->nodes[level]));
-                        btrfs_tree_lock(next);
-                }
+                WARN_ON(!btrfs_tree_locked(path->nodes[level]));
+                btrfs_tree_lock(next);
         }
 done:
         unlock_up(path, 0, 1);
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 692b8ea42de1..9ea12d42741c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -336,7 +336,6 @@ struct btrfs_path {
         /* keep some upper locks as we walk down */
         int keep_locks;
         int lowest_level;
-        int skip_locking;
 };
 
 /*
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f638803549e0..ffc363d2fb24 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1684,6 +1684,7 @@ void btrfs_throttle(struct btrfs_root *root)
 #else
                 blk_congestion_wait(WRITE, HZ/20);
 #endif
+
         }
 }
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 890b9e9d8e27..0905653dd3fc 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -88,7 +88,6 @@ static int cache_block_group(struct btrfs_root *root,
                 return -ENOMEM;
 
         path->reada = 2;
-        path->skip_locking = 1;
         first_free = block_group->key.objectid;
         key.objectid = block_group->key.objectid;
         key.offset = 0;