Btrfs: don't preallocate metadata blocks during btrfs_search_slot

In order to avoid doing expensive extent management with tree locks held,
btrfs_search_slot will preallocate tree blocks for use by COW without
any tree locks held.

A later commit moves all of the extent allocation work for COW into
a delayed update mechanism, and this preallocation will no longer be
required.

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

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 37f31b5..87c9038 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -254,18 +254,13 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
  * empty_size -- a hint that you plan on doing more cow.  This is the size in
  * bytes the allocator should try to find free next to the block it returns.
  * This is just a hint and may be ignored by the allocator.
- *
- * prealloc_dest -- if you have already reserved a destination for the cow,
- * this uses that block instead of allocating a new one.
- * btrfs_alloc_reserved_extent is used to finish the allocation.
  */
 static noinline 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,
-                            u64 search_start, u64 empty_size,
-                            u64 prealloc_dest)
+                            u64 search_start, u64 empty_size)
 {
        u64 parent_start;
        struct extent_buffer *cow;
@@ -291,26 +286,10 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
        level = btrfs_header_level(buf);
        nritems = btrfs_header_nritems(buf);
 
-       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, parent_start,
-                                                 root->root_key.objectid,
-                                                 trans->transid, level, &ins);
-               BUG_ON(ret);
-               cow = btrfs_init_new_buffer(trans, root, prealloc_dest,
-                                           buf->len, level);
-       } else {
-               cow = btrfs_alloc_free_block(trans, root, buf->len,
-                                            parent_start,
-                                            root->root_key.objectid,
-                                            trans->transid, level,
-                                            search_start, empty_size);
-       }
+       cow = btrfs_alloc_free_block(trans, root, buf->len,
+                                    parent_start, root->root_key.objectid,
+                                    trans->transid, level,
+                                    search_start, empty_size);
        if (IS_ERR(cow))
                return PTR_ERR(cow);
 
@@ -413,7 +392,7 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 noinline 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, u64 prealloc_dest)
+                   struct extent_buffer **cow_ret)
 {
        u64 search_start;
        int ret;
@@ -436,7 +415,6 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
            btrfs_header_owner(buf) == root->root_key.objectid &&
            !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
                *cow_ret = buf;
-               WARN_ON(prealloc_dest);
                return 0;
        }
 
@@ -447,8 +425,7 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
        btrfs_set_lock_blocking(buf);
 
        ret = __btrfs_cow_block(trans, root, buf, parent,
-                                parent_slot, cow_ret, search_start, 0,
-                                prealloc_dest);
+                                parent_slot, cow_ret, search_start, 0);
        return ret;
 }
 
@@ -617,7 +594,7 @@ 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), 0);
+                                           (end_slot - i) * blocksize));
                if (err) {
                        btrfs_tree_unlock(cur);
                        free_extent_buffer(cur);
@@ -937,7 +914,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
                BUG_ON(!child);
                btrfs_tree_lock(child);
                btrfs_set_lock_blocking(child);
-               ret = btrfs_cow_block(trans, root, child, mid, 0, &child, 0);
+               ret = btrfs_cow_block(trans, root, child, mid, 0, &child);
                BUG_ON(ret);
 
                spin_lock(&root->node_lock);
@@ -979,7 +956,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
                btrfs_tree_lock(left);
                btrfs_set_lock_blocking(left);
                wret = btrfs_cow_block(trans, root, left,
-                                      parent, pslot - 1, &left, 0);
+                                      parent, pslot - 1, &left);
                if (wret) {
                        ret = wret;
                        goto enospc;
@@ -990,7 +967,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
                btrfs_tree_lock(right);
                btrfs_set_lock_blocking(right);
                wret = btrfs_cow_block(trans, root, right,
-                                      parent, pslot + 1, &right, 0);
+                                      parent, pslot + 1, &right);
                if (wret) {
                        ret = wret;
                        goto enospc;
@@ -1171,7 +1148,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
                        wret = 1;
                } else {
                        ret = btrfs_cow_block(trans, root, left, parent,
-                                             pslot - 1, &left, 0);
+                                             pslot - 1, &left);
                        if (ret)
                                wret = 1;
                        else {
@@ -1222,7 +1199,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
                } else {
                        ret = btrfs_cow_block(trans, root, right,
                                              parent, pslot + 1,
-                                             &right, 0);
+                                             &right);
                        if (ret)
                                wret = 1;
                        else {
@@ -1492,7 +1469,6 @@ 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 > 0);
@@ -1501,8 +1477,6 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
        if (ins_len < 0)
                lowest_unlock = 2;
 
-       prealloc_block.objectid = 0;
-
 again:
        if (p->skip_locking)
                b = btrfs_root_node(root);
@@ -1529,44 +1503,11 @@ again:
                            !btrfs_header_flag(b, BTRFS_HEADER_FLAG_WRITTEN)) {
                                goto cow_done;
                        }
-
-                       /* ok, we have to cow, is our old prealloc the right
-                        * size?
-                        */
-                       if (prealloc_block.objectid &&
-                           prealloc_block.offset != b->len) {
-                               btrfs_release_path(root, p);
-                               btrfs_free_reserved_extent(root,
-                                          prealloc_block.objectid,
-                                          prealloc_block.offset);
-                               prealloc_block.objectid = 0;
-                               goto again;
-                       }
-
-                       /*
-                        * for higher level blocks, try not to allocate blocks
-                        * with the block and the parent locks held.
-                        */
-                       if (level > 0 && !prealloc_block.objectid) {
-                               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;
-                       }
-
                        btrfs_set_path_blocking(p);
 
                        wret = btrfs_cow_block(trans, root, b,
                                               p->nodes[level + 1],
-                                              p->slots[level + 1],
-                                              &b, prealloc_block.objectid);
-                       prealloc_block.objectid = 0;
+                                              p->slots[level + 1], &b);
                        if (wret) {
                                free_extent_buffer(b);
                                ret = wret;
@@ -1743,11 +1684,6 @@ done:
         * from here on, so for now just mark it as blocking
         */
        btrfs_set_path_blocking(p);
-       if (prealloc_block.objectid) {
-               btrfs_free_reserved_extent(root,
-                          prealloc_block.objectid,
-                          prealloc_block.offset);
-       }
        return ret;
 }
 
@@ -1768,7 +1704,7 @@ int btrfs_merge_path(struct btrfs_trans_handle *trans,
        int ret;
 
        eb = btrfs_lock_root_node(root);
-       ret = btrfs_cow_block(trans, root, eb, NULL, 0, &eb, 0);
+       ret = btrfs_cow_block(trans, root, eb, NULL, 0, &eb);
        BUG_ON(ret);
 
        btrfs_set_lock_blocking(eb);
@@ -1826,7 +1762,7 @@ int btrfs_merge_path(struct btrfs_trans_handle *trans,
                        }
 
                        ret = btrfs_cow_block(trans, root, eb, parent, slot,
-                                             &eb, 0);
+                                             &eb);
                        BUG_ON(ret);
 
                        if (root->root_key.objectid ==
@@ -2377,7 +2313,7 @@ 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, 0);
+                             slot + 1, &right);
        if (ret)
                goto out_unlock;
 
@@ -2576,7 +2512,7 @@ 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, 0);
+                             path->nodes[1], slot - 1, &left);
        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 5e1d4e3..3a37ba7 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1838,7 +1838,7 @@ 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, u64 prealloc_dest);
+                   struct extent_buffer **cow_ret);
 int btrfs_copy_root(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      struct extent_buffer *buf,

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 4112d53..d638c54 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -463,7 +463,7 @@ int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
        btrfs_extent_post_op(trans, fs_info->tree_root);
 
        eb = btrfs_lock_root_node(fs_info->tree_root);
-       btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb, 0);
+       btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb);
        btrfs_tree_unlock(eb);
        free_extent_buffer(eb);
 
@@ -766,7 +766,7 @@ 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, 0);
+       btrfs_cow_block(trans, root, old, NULL, 0, &old);
 
        btrfs_copy_root(trans, root, old, &tmp, objectid);
        btrfs_tree_unlock(old);