On Thu, Apr 12, 2012 at 05:53:15PM +0200, Jan Schmidt wrote:
> Hi Mark,
>
> While reading 3/3 I stumbled across one more thing in this one:
>
> On 05.04.2012 22:09, Mark Fasheh wrote:
> > +int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
> > + u64 start_off, struct btrfs_path *path,
> > + struct btrfs_inode_extref **ret_ref, u64 *found_off)
> > +{
> > + int ret, slot;
> > + struct btrfs_key key, found_key;
> > + struct btrfs_inode_extref *ref;
> > + struct extent_buffer *leaf;
> > + struct btrfs_item *item;
> > + unsigned long ptr;
> >
> > -/*
> > - * There are a few corners where the link count of the file can't
> > - * be properly maintained during replay. So, instead of adding
> > - * lots of complexity to the log code, we just scan the backrefs
> > - * for any file that has been through replay.
> > - *
> > - * The scan will update the link count on the inode to reflect the
> > - * number of back refs found. If it goes down to zero, the iput
> > - * will free the inode.
> > - */
> > -static noinline int fixup_inode_link_count(struct btrfs_trans_handle *trans,
> > - struct btrfs_root *root,
> > - struct inode *inode)
> > + key.objectid = inode_objectid;
> > + btrfs_set_key_type(&key, BTRFS_INODE_EXTREF_KEY);
> > + key.offset = start_off;
> > +
> > + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
> > + if (ret < 0)
> > + goto out;
> > +
> > + while (1) {
> > + leaf = path->nodes[0];
> > + slot = path->slots[0];
> > + if (slot >= btrfs_header_nritems(leaf)) {
> > + /*
> > + * If the item at offset is not found,
> > + * btrfs_search_slot will point us to the slot
> > + * where it should be inserted. In our case
> > + * that will be the slot directly before the
> > + * next INODE_REF_KEY_V2 item. In the case
> > + * that we're pointing to the last slot in a
> > + * leaf, we must move one leaf over.
> > + */
> > + ret = btrfs_next_leaf(root, path);
> > + if (ret) {
> > + if (ret >= 1)
> > + ret = -ENOENT;
> > + break;
> > + }
> > + continue;
> > + }
> > +
> > + item = btrfs_item_nr(leaf, slot);
> > + btrfs_item_key_to_cpu(leaf, &found_key, slot);
> > +
> > + /*
> > + * Check that we're still looking at an extended ref key for
> > + * this particular objectid. If we have different
> > + * objectid or type then there are no more to be found
> > + * in the tree and we can exit.
> > + */
> > + ret = -ENOENT;
> > + if (found_key.objectid != inode_objectid)
> > + break;
> > + if (btrfs_key_type(&found_key) != BTRFS_INODE_EXTREF_KEY)
> > + break;
> > +
> > + ret = 0;
> > + ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
> > + ref = (struct btrfs_inode_extref *)ptr;
> > + *ret_ref = ref;
> > + if (found_off)
> > + *found_off = found_key.offset + 1;
> ^^^
> It's evil to call it "found offset" an then return one larger than the
> offset found. No caller would ever expect this.
>
> > + break;
> > + }
> > +
> > +out:
> > + return ret;
> > +}
> > +
> > +static int count_inode_extrefs(struct btrfs_root *root,
> > + struct inode *inode, struct btrfs_path *path)
> > +{
> > + int ret;
> > + unsigned int nlink = 0;
> > + u64 inode_objectid = btrfs_ino(inode);
> > + u64 offset = 0;
> > + struct btrfs_inode_extref *ref;
> > +
> > + while (1) {
> > + ret = btrfs_find_one_extref(root, inode_objectid, offset, path,
> > + &ref, &offset);
> > + if (ret)
> > + break;
> > +
> > + nlink++;
> > + offset++;
> ^^^^^^^^
> Huh. See? The caller expected to get the offset found from
> btrfs_find_one_extref. As it stands you might be missing the very next key.
Oh yeah that was totally broken btw. Fixed now, but forgot to mention that
:)
btrfs_find_one_extref() now returns the actual found offset (and the callers
can just increment if they're doing a search).
--Mark
--
Mark Fasheh
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