On Mon, 2008-08-18 at 15:47 -0400, Chris Mason wrote:
> Lets pretend I had put in commments something like the code below.
> The important part is that directories have only one link, so they
> have only one backref.
OK. Now can I rip that code out anyway? The VFS will never call
btrfs_lookup() for ".." -- not since the 2.2 kernel :)
I'm still a little confused about precisely what btrfs_search_slot()
returns when it doesn't find a match -- that's probably where the
documentation would be more useful.
What I have in btrfs_get_parent() is correct, I think -- but could
probably be simplified to your version, searching for (u64)-1 and then
not needing to call btrfs_next_leaf().
Something like this?
(And am I fixing a use-after-free bug by moving that btrfs_free_path()
down by a line, at the end?)
diff --git a/export.c b/export.c
index 797b4cb..830e87a 100644
--- a/export.c
+++ b/export.c
@@ -156,27 +156,27 @@ static struct dentry *btrfs_get_parent(struct dentry *child)
key.objectid = dir->i_ino;
btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
- key.offset = 0;
+ key.offset = (u64)-1;
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
- BUG_ON(ret == 0);
- ret = 0;
leaf = path->nodes[0];
slot = path->slots[0];
- nritems = btrfs_header_nritems(leaf);
- if (slot >= nritems) {
- ret = btrfs_next_leaf(root, path);
- if (ret) {
- btrfs_free_path(path);
- goto out;
- }
- leaf = path->nodes[0];
- slot = path->slots[0];
+ if (ret < 0 && slot == 0) {
+ btrfs_free_path(path);
+ goto out;
}
+ /*
+ This will be in the slot _before_ the one that btrfs_search_slot()
+ returns. And for some reason which dwmw2 doesn't quite understand,
+ that'll definitely be in the same leaf that btrfs_search_slot()
+ returned -- even if btrfs_search_slot() had to look in the _next_
+ leaf to find the first key which is greater than what we asked for
+ */
+ slot--;
+ btrfs_item_key_to_cpu(leaf, &key, slot);
btrfs_free_path(path);
- btrfs_item_key_to_cpu(leaf, &key, slot);
if (key.objectid != dir->i_ino || key.type != BTRFS_INODE_REF_KEY)
goto out;
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@xxxxxxxxx Intel Corporation
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