At find_parent_nodes(), at its last step, when iterating over all direct
references, we are checking if we have a share context and if we have
a reference with a different root from the one in the share context.
However that logic is pointless because of two reasons:
1) After the previous patch in the series (subject "btrfs: remove roots
ulist when checking data extent sharedness"), the roots argument is
always NULL when using a share check context (struct share_check), so
this code is never triggered;
2) Even before that previous patch, we could not hit this code because
if we had a reference with a root different from the one in our share
context, then we would have exited earlier when doing either of the
following:
- Adding a second direct ref to the direct refs red black tree
resulted in extent_is_shared() returning true when called from
add_direct_ref() -> add_prelim_ref(), after processing delayed
references or while processing references in the extent tree;
- When adding a second reference to the indirect refs red black
tree (same as above, extent_is_shared() returns true);
- If we only have one indirect reference and no direct references,
then when resolving it at resolve_indirect_refs() we immediately
return that the target extent is shared, therefore never reaching
that loop that iterates over all direct references at
find_parent_nodes();
- If we have 1 indirect reference and 1 direct reference, then we
also exit early because extent_is_shared() ends up returning true
when called through add_prelim_ref() (by add_direct_ref() or
add_indirect_ref()) or add_delayed_refs(). Same applies as when
having a combination of direct, indirect and indirect with missing
key references.
This logic had been obsoleted since commit
3ec4d3238ab165 ("btrfs:
allow backref search checks for shared extents"), which introduced the
early exits in case an extent is shared.
So just remove that logic, and assert at find_parent_nodes() that when we
have a share context we don't have a roots ulist and that we haven't found
the extent to be directly shared after processing delayed references and
all references from the extent tree.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
.indirect_missing_keys = PREFTREE_INIT
};
+ /* Roots ulist is not needed when using a sharedness check context. */
+ if (sc)
+ ASSERT(roots == NULL);
+
key.objectid = bytenr;
key.offset = (u64)-1;
if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
}
}
+ /*
+ * If we have a share context and we reached here, it means the extent
+ * is not directly shared (no multiple reference items for it),
+ * otherwise we would have exited earlier with a return value of
+ * BACKREF_FOUND_SHARED after processing delayed references or while
+ * processing inline or keyed references from the extent tree.
+ * The extent may however be indirectly shared through shared subtrees
+ * as a result from creating snapshots, so we determine below what is
+ * its parent node, in case we are dealing with a metadata extent, or
+ * what's the leaf (or leaves), from a fs tree, that has a file extent
+ * item pointing to it in case we are dealing with a data extent.
+ */
+ ASSERT(extent_is_shared(sc) == 0);
+
btrfs_release_path(path);
ret = add_missing_keys(fs_info, &preftrees, path->skip_locking == 0);
* and would retain their original ref->count < 0.
*/
if (roots && ref->count && ref->root_id && ref->parent == 0) {
- if (sc && ref->root_id != sc->root_objectid) {
- ret = BACKREF_FOUND_SHARED;
- goto out;
- }
-
/* no parent == root of tree */
ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
if (ret < 0)