Btrfs: Fix split_leaf to detect when it is extending an item

When making room for a new item, it is ok to create an empty leaf, but
when making room to extend an item, split_leaf needs to make sure it
keeps the item we're extending in the path and make sure we don't end up
with an empty leaf.

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

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 53e40b5..3eb5a9f 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -26,7 +26,7 @@ static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_path *path, int level);
 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);
+                     struct btrfs_path *path, int data_size, int extend);
 static int push_node_left(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, struct extent_buffer *dst,
                          struct extent_buffer *src);
@@ -1049,7 +1049,7 @@ again:
                        if (ins_len > 0 && btrfs_leaf_free_space(root, b) <
                            sizeof(struct btrfs_item) + ins_len) {
                                int sret = split_leaf(trans, root, key,
-                                                     p, ins_len);
+                                                     p, ins_len, ret == 0);
                                BUG_ON(sret > 0);
                                if (sret)
                                        return sret;
@@ -1755,7 +1755,7 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
  */
 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)
+                     struct btrfs_path *path, int data_size, int extend)
 {
        struct extent_buffer *l;
        u32 nritems;
@@ -1768,9 +1768,13 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
        int i;
        int ret = 0;
        int wret;
-       int double_split = 0;
+       int double_split;
+       int num_doubles = 0;
        struct btrfs_disk_key disk_key;
 
+       if (extend)
+               space_needed = data_size;
+
        /* first try to make some room by pushing left and right */
        if (ins_key->type != BTRFS_DIR_ITEM_KEY) {
                wret = push_leaf_right(trans, root, path, data_size);
@@ -1785,12 +1789,8 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
                l = path->nodes[0];
 
                /* did the pushes work? */
-               if (btrfs_leaf_free_space(root, l) >=
-                   sizeof(struct btrfs_item) + data_size) {
+               if (btrfs_leaf_free_space(root, l) >= space_needed)
                        return 0;
-               }
-       } else {
-               l = path->nodes[0];
        }
 
        if (!path->nodes[1]) {
@@ -1798,6 +1798,9 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
                if (ret)
                        return ret;
        }
+again:
+       double_split = 0;
+       l = path->nodes[0];
        slot = path->slots[0];
        nritems = btrfs_header_nritems(l);
        mid = (nritems + 1)/ 2;
@@ -1815,7 +1818,6 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
        write_extent_buffer(right, root->fs_info->fsid,
                            (unsigned long)btrfs_header_fsid(right),
                            BTRFS_FSID_SIZE);
-
        if (mid <= slot) {
                if (nritems == 1 ||
                    leaf_space_used(l, mid, nritems - mid) + space_needed >
@@ -1844,7 +1846,7 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
        } else {
                if (leaf_space_used(l, 0, mid + 1) + space_needed >
                        BTRFS_LEAF_DATA_SIZE(root)) {
-                       if (slot == 0) {
+                       if (!extend && slot == 0) {
                                btrfs_cpu_key_to_disk(&disk_key, ins_key);
                                btrfs_set_header_nritems(right, 0);
                                wret = insert_ptr(trans, root, path,
@@ -1863,12 +1865,15 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
                                                ret = wret;
                                }
                                return ret;
-                       }
-                       mid = slot;
-                       if (mid != nritems &&
-                           leaf_space_used(l, mid, nritems - mid) +
-                           space_needed > BTRFS_LEAF_DATA_SIZE(root)) {
-                               double_split = 1;
+                       } else if (extend && slot == 0) {
+                               mid = 1;
+                       } else {
+                               mid = slot;
+                               if (mid != nritems &&
+                                   leaf_space_used(l, mid, nritems - mid) +
+                                   space_needed > BTRFS_LEAF_DATA_SIZE(root)) {
+                                       double_split = 1;
+                               }
                        }
                }
        }
@@ -1931,39 +1936,11 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
 
        BUG_ON(path->slots[0] < 0);
 
-       if (!double_split) {
-               return ret;
-       }
-
-       right = btrfs_alloc_free_block(trans, root, root->leafsize,
-                                      l->start, 0);
-       if (IS_ERR(right))
-               return PTR_ERR(right);
-
-       memset_extent_buffer(right, 0, 0, sizeof(struct btrfs_header));
-       btrfs_set_header_bytenr(right, right->start);
-       btrfs_set_header_generation(right, trans->transid);
-       btrfs_set_header_owner(right, root->root_key.objectid);
-       btrfs_set_header_level(right, 0);
-       write_extent_buffer(right, root->fs_info->fsid,
-                           (unsigned long)btrfs_header_fsid(right),
-                           BTRFS_FSID_SIZE);
-
-       btrfs_cpu_key_to_disk(&disk_key, ins_key);
-       btrfs_set_header_nritems(right, 0);
-       wret = insert_ptr(trans, root, path,
-                         &disk_key, right->start,
-                         path->slots[1], 1);
-       if (wret)
-               ret = wret;
-       if (path->slots[1] == 0) {
-               wret = fixup_low_keys(trans, root, path, &disk_key, 1);
-               if (wret)
-                       ret = wret;
+       if (double_split) {
+               BUG_ON(num_doubles != 0);
+               num_doubles++;
+               goto again;
        }
-       free_extent_buffer(path->nodes[0]);
-       path->nodes[0] = right;
-       path->slots[0] = 0;
        return ret;
 }
 
@@ -1992,8 +1969,7 @@ int btrfs_truncate_item(struct btrfs_trans_handle *trans,
 
        slot = path->slots[0];
        old_data_start = btrfs_item_offset_nr(leaf, slot);
-       old_size = btrfs_item_size_nr(leaf, slot);
-       BUG_ON(old_size <= new_size);
+       old_size = btrfs_item_size_nr(leaf, slot); BUG_ON(old_size <= new_size);
        size_diff = old_size - new_size;
 
        BUG_ON(slot < 0);