Qu Wenruo wrote on 2015/10/06 08:58 +0800:
Normal btrfs_item_key_to_cpu() will need extent buffer to do it, and
there is not stack version to handle in memory leaf.

Add btrfs_stack_item_key_to_cpu() function for such operation, which
will provide the basis for later qgroup fix.

Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
v2:
   Change the char* parameter to struct btrfs_header *, as a leaf always
   starts with a header.
---
  fs/btrfs/ctree.h | 20 ++++++++++++++++++++
  1 file changed, 20 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 938efe3..4864dfe 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2683,6 +2683,17 @@ static inline void btrfs_item_key(struct extent_buffer 
*eb,
        read_eb_member(eb, item, struct btrfs_item, key, disk_key);
  }

+static inline void btrfs_stack_item_key(struct btrfs_header *stack_leaf,
+                                       struct btrfs_disk_key *disk_key,
+                                       int nr)
+{
+       unsigned long item_offset = btrfs_item_nr_offset(nr);
+       struct btrfs_item *item;
+
+       item = (struct btrfs_item *)(stack_leaf + item_offset);
Please ignore this version, as I changed the type of stack_leaf but didn't force convert it to (char *).

I'll update it soon.

Thanks,
Qu
+       memcpy(disk_key, &item->key, sizeof(*disk_key));
+}
+
  static inline void btrfs_set_item_key(struct extent_buffer *eb,
                               struct btrfs_disk_key *disk_key, int nr)
  {
@@ -2785,6 +2796,15 @@ static inline void btrfs_item_key_to_cpu(struct 
extent_buffer *eb,
        btrfs_disk_key_to_cpu(key, &disk_key);
  }

+static inline void btrfs_stack_item_key_to_cpu(struct btrfs_header *stack_leaf,
+                                              struct btrfs_key *key,
+                                              int nr)
+{
+       struct btrfs_disk_key disk_key;
+       btrfs_stack_item_key(stack_leaf, &disk_key, nr);
+       btrfs_disk_key_to_cpu(key, &disk_key);
+}
+
  static inline void btrfs_dir_item_key_to_cpu(struct extent_buffer *eb,
                                      struct btrfs_dir_item *item,
                                      struct btrfs_key *key)

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