[PATCH 02/40] btrfs: backref: Implement btrfs_backref_iter_next()

Qu Wenruo
2020-03-23T10:24:34Z

This function will go next inline/keyed backref for
btrfs_backref_iter infrastructure.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/backref.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/backref.h | 34 +++++++++++++++++++++++++++
2 files changed, 92 insertions(+)

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 8de80ae76008..aee06eff3a04 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -2409,3 +2409,61 @@ int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr)
btrfs_backref_iter_release(iter);
return ret;
}
+
+/*
+ * Go to next backref item of current bytenr, can be either inlined or keyed.
+ *
+ * Caller need to check whether it's inline ref or not by iter->cur_key.
+ *
+ * Return 0 if we get next backref without problem.
+ * Return >0 if there is no extra backref for this bytenr.
+ * Return <0 if there is something wrong happened.
+ */
+int btrfs_backref_iter_next(struct btrfs_backref_iter *iter)
+{
+ struct extent_buffer *eb = btrfs_backref_get_eb(iter);
+ struct btrfs_path *path = iter->path;
+ struct btrfs_extent_inline_ref *iref;
+ int ret;
+ u32 size;
+
+ if (btrfs_backref_iter_is_inline_ref(iter)) {
+ /* We're still inside the inline refs */
+ ASSERT(iter->cur_ptr < iter->end_ptr);
+
+ if (btrfs_backref_has_tree_block_info(iter)) {
+ /* First tree block info */
+ size = sizeof(struct btrfs_tree_block_info);
+ } else {
+ /* Use inline ref type to determine the size */
+ int type;
+
+ iref = (struct btrfs_extent_inline_ref *)
+ ((unsigned long)iter->cur_ptr);
+ type = btrfs_extent_inline_ref_type(eb, iref);
+
+ size = btrfs_extent_inline_ref_size(type);
+ }
+ iter->cur_ptr += size;
+ if (iter->cur_ptr < iter->end_ptr)
+ return 0;
+
+ /* All inline items iterated, fall through */
+ }
+ /* We're at keyed items, there is no inline item, just go next item */
+ ret = btrfs_next_item(iter->fs_info->extent_root, iter->path);
+ if (ret)
+ return ret;
+
+ btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key, path->slots[0]);
+ if (iter->cur_key.objectid != iter->bytenr ||
+ (iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
+ iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY))
+ return 1;
+ iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
+ path->slots[0]);
+ iter->cur_ptr = iter->item_ptr;
+ iter->end_ptr = iter->item_ptr + (u32)btrfs_item_size_nr(path->nodes[0],
+ path->slots[0]);
+ return 0;
+}
diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
index 3ca9604981f8..29cc74eabda3 100644
--- a/fs/btrfs/backref.h
+++ b/fs/btrfs/backref.h
@@ -100,8 +100,42 @@ static inline void btrfs_backref_iter_free(struct btrfs_backref_iter *iter)
kfree(iter);
}

+static inline struct extent_buffer *
+btrfs_backref_get_eb(struct btrfs_backref_iter *iter)
+{
+ if (!iter)
+ return NULL;
+ return iter->path->nodes[0];
+}
+
+/*
+ * For metadata with EXTENT_ITEM key (non-skinny) case, the first inline data
+ * is btrfs_tree_block_info, without a btrfs_extent_inline_ref header.
+ *
+ * This helper is here to determine if that's the case.
+ */
+static inline bool btrfs_backref_has_tree_block_info(
+ struct btrfs_backref_iter *iter)
+{
+ if (iter->cur_key.type == BTRFS_EXTENT_ITEM_KEY &&
+ iter->cur_ptr - iter->item_ptr == sizeof(struct btrfs_extent_item))
+ return true;
+ return false;
+}
+
int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr);

+int btrfs_backref_iter_next(struct btrfs_backref_iter *iter);
+
+static inline bool
+btrfs_backref_iter_is_inline_ref(struct btrfs_backref_iter *iter)
+{
+ if (iter->cur_key.type == BTRFS_EXTENT_ITEM_KEY ||
+ iter->cur_key.type == BTRFS_METADATA_ITEM_KEY)
+ return true;
+ return false;
+}
+
static inline void
btrfs_backref_iter_release(struct btrfs_backref_iter *iter)
{
--
2.25.2