Btrfs: Add a write ahead tree log to optimize synchronous operations

File syncs and directory syncs are optimized by copying their
items into a special (copy-on-write) log tree.  There is one log tree per
subvolume and the btrfs super block points to a tree of log tree roots.

After a crash, items are copied out of the log tree and back into the
subvolume.  See tree-log.c for all the details.

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

1 files changed, 54 insertions, 19 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 7114faafa9d4..579124043d9b 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -60,7 +60,7 @@ void btrfs_free_path(struct btrfs_path *p)
         kmem_cache_free(btrfs_path_cachep, p);
 }
 
-void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
+void noinline btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
 {
         int i;
 
@@ -176,7 +176,7 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
         return 0;
 }
 
-int __btrfs_cow_block(struct btrfs_trans_handle *trans,
+int noinline __btrfs_cow_block(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct extent_buffer *buf,
                              struct extent_buffer *parent, int parent_slot,
@@ -294,7 +294,7 @@ int __btrfs_cow_block(struct btrfs_trans_handle *trans,
         return 0;
 }
 
-int btrfs_cow_block(struct btrfs_trans_handle *trans,
+int noinline 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, u64 prealloc_dest)
@@ -677,9 +677,10 @@ static int noinline check_block(struct btrfs_root *root,
  *
  * slot may point to max if the key is bigger than all of the keys
  */
-static int generic_bin_search(struct extent_buffer *eb, unsigned long p,
-                              int item_size, struct btrfs_key *key,
-                              int max, int *slot)
+static noinline int generic_bin_search(struct extent_buffer *eb,
+                                       unsigned long p,
+                                       int item_size, struct btrfs_key *key,
+                                       int max, int *slot)
 {
         int low = 0;
         int high = max;
@@ -765,7 +766,7 @@ static int bin_search(struct extent_buffer *eb, struct btrfs_key *key,
         return -1;
 }
 
-static struct extent_buffer *read_node_slot(struct btrfs_root *root,
+static noinline struct extent_buffer *read_node_slot(struct btrfs_root *root,
                                    struct extent_buffer *parent, int slot)
 {
         int level = btrfs_header_level(parent);
@@ -781,7 +782,7 @@ static struct extent_buffer *read_node_slot(struct btrfs_root *root,
                        btrfs_node_ptr_generation(parent, slot));
 }
 
-static int balance_level(struct btrfs_trans_handle *trans,
+static noinline int balance_level(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root,
                          struct btrfs_path *path, int level)
 {
@@ -1128,8 +1129,9 @@ static int noinline push_nodes_for_insert(struct btrfs_trans_handle *trans,
 /*
  * readahead one full node of leaves
  */
-static void reada_for_search(struct btrfs_root *root, struct btrfs_path *path,
-                             int level, int slot, u64 objectid)
+static noinline 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;
@@ -1201,7 +1203,8 @@ static void reada_for_search(struct btrfs_root *root, struct btrfs_path *path,
         }
 }
 
-static void unlock_up(struct btrfs_path *path, int level, int lowest_unlock)
+static noinline void unlock_up(struct btrfs_path *path, int level,
+                               int lowest_unlock)
 {
         int i;
         int skip_level = level;
@@ -1759,8 +1762,9 @@ static int insert_ptr(struct btrfs_trans_handle *trans, struct btrfs_root
  *
  * returns 0 on success and < 0 on failure
  */
-static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
-                      *root, struct btrfs_path *path, int level)
+static noinline int split_node(struct btrfs_trans_handle *trans,
+                               struct btrfs_root *root,
+                               struct btrfs_path *path, int level)
 {
         u64 root_gen;
         struct extent_buffer *c;
@@ -1874,7 +1878,8 @@ static int leaf_space_used(struct extent_buffer *l, int start, int nr)
  * the start of the leaf data.  IOW, how much room
  * the leaf has left for both items and data
  */
-int btrfs_leaf_free_space(struct btrfs_root *root, struct extent_buffer *leaf)
+int noinline btrfs_leaf_free_space(struct btrfs_root *root,
+                                   struct extent_buffer *leaf)
 {
         int nritems = btrfs_header_nritems(leaf);
         int ret;
@@ -2283,9 +2288,11 @@ out:
  *
  * returns 0 if all went well and < 0 on failure.
  */
-static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
-                      *root, struct btrfs_key *ins_key,
-                      struct btrfs_path *path, int data_size, int extend)
+static noinline int split_leaf(struct btrfs_trans_handle *trans,
+                               struct btrfs_root *root,
+                               struct btrfs_key *ins_key,
+                               struct btrfs_path *path, int data_size,
+                               int extend)
 {
         u64 root_gen;
         struct extent_buffer *l;
@@ -3079,6 +3086,7 @@ int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
  * was nothing in the tree that matched the search criteria.
  */
 int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
+                         struct btrfs_key *max_key,
                          struct btrfs_path *path, int cache_only,
                          u64 min_trans)
 {
@@ -3093,6 +3101,7 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
 again:
         cur = btrfs_lock_root_node(root);
         level = btrfs_header_level(cur);
+        WARN_ON(path->nodes[level]);
         path->nodes[level] = cur;
         path->locks[level] = 1;
 
@@ -3107,6 +3116,8 @@ again:
 
                 /* at level = 0, we're done, setup the path and exit */
                 if (level == 0) {
+                        if (slot >= nritems)
+                                goto find_next_key;
                         ret = 0;
                         path->slots[level] = slot;
                         btrfs_item_key_to_cpu(cur, &found_key, slot);
@@ -3123,6 +3134,8 @@ again:
                         u64 blockptr;
                         u64 gen;
                         struct extent_buffer *tmp;
+                        struct btrfs_disk_key disk_key;
+
                         blockptr = btrfs_node_blockptr(cur, slot);
                         gen = btrfs_node_ptr_generation(cur, slot);
                         if (gen < min_trans) {
@@ -3132,6 +3145,14 @@ again:
                         if (!cache_only)
                                 break;
 
+                        if (max_key) {
+                                btrfs_node_key(cur, &disk_key, slot);
+                                if (comp_keys(&disk_key, max_key) >= 0) {
+                                        ret = 1;
+                                        goto out;
+                                }
+                        }
+
                         tmp = btrfs_find_tree_block(root, blockptr,
                                             btrfs_level_size(root, level - 1));
 
@@ -3143,14 +3164,16 @@ again:
                                 free_extent_buffer(tmp);
                         slot++;
                 }
+find_next_key:
                 /*
                  * we didn't find a candidate key in this node, walk forward
                  * and find another one
                  */
                 if (slot >= nritems) {
-                        ret = btrfs_find_next_key(root, path, min_key, level,
+                        path->slots[level] = slot;
+                        sret = btrfs_find_next_key(root, path, min_key, level,
                                                   cache_only, min_trans);
-                        if (ret == 0) {
+                        if (sret == 0) {
                                 btrfs_release_path(root, path);
                                 goto again;
                         } else {
@@ -3351,6 +3374,7 @@ int btrfs_previous_item(struct btrfs_root *root,
 {
         struct btrfs_key found_key;
         struct extent_buffer *leaf;
+        u32 nritems;
         int ret;
 
         while(1) {
@@ -3362,9 +3386,20 @@ int btrfs_previous_item(struct btrfs_root *root,
                         path->slots[0]--;
                 }
                 leaf = path->nodes[0];
+                nritems = btrfs_header_nritems(leaf);
+                if (nritems == 0)
+                        return 1;
+                if (path->slots[0] == nritems)
+                        path->slots[0]--;
+
                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                 if (found_key.type == type)
                         return 0;
+                if (found_key.objectid < min_objectid)
+                        break;
+                if (found_key.objectid == min_objectid &&
+                    found_key.type < type)
+                        break;
         }
         return 1;
 }