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>

1 files changed, 27 insertions, 51 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 53e40b5c084d..3eb5a9f30d14 100644
--- 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);