Btrfs: break up btrfs_search_slot into smaller pieces

btrfs_search_slot was doing too many things at once.  This breaks
it up into more reasonable units.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 131 insertions, 90 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index dbb724124633..271b05e507d7 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1244,9 +1244,9 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
  * readahead one full node of leaves, finding things that are close
  * to the block in 'slot', and triggering ra on them.
  */
-static noinline void reada_for_search(struct btrfs_root *root,
-                                      struct btrfs_path *path,
-                                      int level, int slot, u64 objectid)
+static void reada_for_search(struct btrfs_root *root,
+                             struct btrfs_path *path,
+                             int level, int slot, u64 objectid)
 {
         struct extent_buffer *node;
         struct btrfs_disk_key disk_key;
@@ -1447,6 +1447,117 @@ noinline void btrfs_unlock_up_safe(struct btrfs_path *path, int level)
 }
 
 /*
+ * helper function for btrfs_search_slot.  The goal is to find a block
+ * in cache without setting the path to blocking.  If we find the block
+ * we return zero and the path is unchanged.
+ *
+ * If we can't find the block, we set the path blocking and do some
+ * reada.  -EAGAIN is returned and the search must be repeated.
+ */
+static int
+read_block_for_search(struct btrfs_trans_handle *trans,
+                       struct btrfs_root *root, struct btrfs_path *p,
+                       struct extent_buffer **eb_ret, int level, int slot,
+                       struct btrfs_key *key)
+{
+        u64 blocknr;
+        u64 gen;
+        u32 blocksize;
+        struct extent_buffer *b = *eb_ret;
+        struct extent_buffer *tmp;
+
+        blocknr = btrfs_node_blockptr(b, slot);
+        gen = btrfs_node_ptr_generation(b, slot);
+        blocksize = btrfs_level_size(root, level - 1);
+
+        tmp = btrfs_find_tree_block(root, blocknr, blocksize);
+        if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
+                *eb_ret = tmp;
+                return 0;
+        }
+
+        /*
+         * reduce lock contention at high levels
+         * of the btree by dropping locks before
+         * we read.
+         */
+        btrfs_release_path(NULL, p);
+        if (tmp)
+                free_extent_buffer(tmp);
+        if (p->reada)
+                reada_for_search(root, p, level, slot, key->objectid);
+
+        tmp = read_tree_block(root, blocknr, blocksize, gen);
+        if (tmp)
+                free_extent_buffer(tmp);
+        return -EAGAIN;
+}
+
+/*
+ * helper function for btrfs_search_slot.  This does all of the checks
+ * for node-level blocks and does any balancing required based on
+ * the ins_len.
+ *
+ * If no extra work was required, zero is returned.  If we had to
+ * drop the path, -EAGAIN is returned and btrfs_search_slot must
+ * start over
+ */
+static int
+setup_nodes_for_search(struct btrfs_trans_handle *trans,
+                       struct btrfs_root *root, struct btrfs_path *p,
+                       struct extent_buffer *b, int level, int ins_len)
+{
+        int ret;
+        if ((p->search_for_split || ins_len > 0) && btrfs_header_nritems(b) >=
+            BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {
+                int sret;
+
+                sret = reada_for_balance(root, p, level);
+                if (sret)
+                        goto again;
+
+                btrfs_set_path_blocking(p);
+                sret = split_node(trans, root, p, level);
+                btrfs_clear_path_blocking(p, NULL);
+
+                BUG_ON(sret > 0);
+                if (sret) {
+                        ret = sret;
+                        goto done;
+                }
+                b = p->nodes[level];
+        } else if (ins_len < 0 && btrfs_header_nritems(b) <
+                   BTRFS_NODEPTRS_PER_BLOCK(root) / 4) {
+                int sret;
+
+                sret = reada_for_balance(root, p, level);
+                if (sret)
+                        goto again;
+
+                btrfs_set_path_blocking(p);
+                sret = balance_level(trans, root, p, level);
+                btrfs_clear_path_blocking(p, NULL);
+
+                if (sret) {
+                        ret = sret;
+                        goto done;
+                }
+                b = p->nodes[level];
+                if (!b) {
+                        btrfs_release_path(NULL, p);
+                        goto again;
+                }
+                BUG_ON(btrfs_header_nritems(b) == 1);
+        }
+        return 0;
+
+again:
+        ret = -EAGAIN;
+done:
+        return ret;
+}
+
+/*
  * look for key in the tree.  path is filled in with nodes along the way
  * if key is found, we return zero and you can find the item in the leaf
  * level of the path (level 0)
@@ -1464,16 +1575,11 @@ 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;
-        int should_reada = p->reada;
         int lowest_unlock = 1;
-        int blocksize;
         u8 lowest_level = 0;
-        u64 blocknr;
-        u64 gen;
 
         lowest_level = p->lowest_level;
         WARN_ON(lowest_level && ins_len > 0);
@@ -1502,7 +1608,11 @@ again:
                 if (cow) {
                         int wret;
 
-                        /* is a cow on this block not required */
+                        /*
+                         * if we don't really need to cow this block
+                         * then we don't want to set the path blocking,
+                         * so we test it here
+                         */
                         if (btrfs_header_generation(b) == trans->transid &&
                             btrfs_header_owner(b) == root->root_key.objectid &&
                             !btrfs_header_flag(b, BTRFS_HEADER_FLAG_WRITTEN)) {
@@ -1557,51 +1667,15 @@ cow_done:
                         if (ret && slot > 0)
                                 slot -= 1;
                         p->slots[level] = slot;
-                        if ((p->search_for_split || ins_len > 0) &&
-                            btrfs_header_nritems(b) >=
-                            BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {
-                                int sret;
-
-                                sret = reada_for_balance(root, p, level);
-                                if (sret)
-                                        goto again;
-
-                                btrfs_set_path_blocking(p);
-                                sret = split_node(trans, root, p, level);
-                                btrfs_clear_path_blocking(p, NULL);
-
-                                BUG_ON(sret > 0);
-                                if (sret) {
-                                        ret = sret;
-                                        goto done;
-                                }
-                                b = p->nodes[level];
-                                slot = p->slots[level];
-                        } else if (ins_len < 0 &&
-                                   btrfs_header_nritems(b) <
-                                   BTRFS_NODEPTRS_PER_BLOCK(root) / 4) {
-                                int sret;
-
-                                sret = reada_for_balance(root, p, level);
-                                if (sret)
-                                        goto again;
-
-                                btrfs_set_path_blocking(p);
-                                sret = balance_level(trans, root, p, level);
-                                btrfs_clear_path_blocking(p, NULL);
+                        ret = setup_nodes_for_search(trans, root, p, b, level,
+                                                     ins_len);
+                        if (ret == -EAGAIN)
+                                goto again;
+                        else if (ret)
+                                goto done;
+                        b = p->nodes[level];
+                        slot = p->slots[level];
 
-                                if (sret) {
-                                        ret = sret;
-                                        goto done;
-                                }
-                                b = p->nodes[level];
-                                if (!b) {
-                                        btrfs_release_path(NULL, p);
-                                        goto again;
-                                }
-                                slot = p->slots[level];
-                                BUG_ON(btrfs_header_nritems(b) == 1);
-                        }
                         unlock_up(p, level, lowest_unlock);
 
                         /* this is only true while dropping a snapshot */
@@ -1610,44 +1684,11 @@ cow_done:
                                 goto done;
                         }
 
-                        blocknr = btrfs_node_blockptr(b, slot);
-                        gen = btrfs_node_ptr_generation(b, slot);
-                        blocksize = btrfs_level_size(root, level - 1);
+                        ret = read_block_for_search(trans, root, p,
+                                                    &b, level, slot, key);
+                        if (ret == -EAGAIN)
+                                goto again;
 
-                        tmp = btrfs_find_tree_block(root, blocknr, blocksize);
-                        if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
-                                b = tmp;
-                        } else {
-                                /*
-                                 * reduce lock contention at high levels
-                                 * of the btree by dropping locks before
-                                 * we read.
-                                 */
-                                if (level > 0) {
-                                        btrfs_release_path(NULL, p);
-                                        if (tmp)
-                                                free_extent_buffer(tmp);
-                                        if (should_reada)
-                                                reada_for_search(root, p,
-                                                                 level, slot,
-                                                                 key->objectid);
-
-                                        tmp = read_tree_block(root, blocknr,
-                                                         blocksize, gen);
-                                        if (tmp)
-                                                free_extent_buffer(tmp);
-                                        goto again;
-                                } else {
-                                        btrfs_set_path_blocking(p);
-                                        if (tmp)
-                                                free_extent_buffer(tmp);
-                                        if (should_reada)
-                                                reada_for_search(root, p,
-                                                                 level, slot,
-                                                                 key->objectid);
-                                        b = read_node_slot(root, b, slot);
-                                }
-                        }
                         if (!p->skip_locking) {
                                 int lret;