96  * the delayed refs are not processed.
100 			     u64 offset, int metadata, u64 *refs, u64 *flags,  in btrfs_lookup_extent_info()  argument
188 			refcount_inc(&head->refs);  in btrfs_lookup_extent_info()
213 	if (refs)  in btrfs_lookup_extent_info()
214 		*refs = num_refs;  in btrfs_lookup_extent_info()
225  * Back reference rules.  Back refs have three main goals:
238  * There are two kinds of back refs. The implicit back refs is optimized
240  * back refs of this kind provide information about the block's owner tree
242  * b-tree searching. The full back refs is for pointers in tree blocks not
244  * in the back refs. Actually the full back refs is generic, and can be
245  * used in all cases the implicit back refs is used. The major shortcoming
246  * of the full back refs is its overhead. Every time a tree block gets
247  * COWed, we have to update back refs entry for all pointers in it.
249  * For a newly allocated tree block, we use implicit back refs for
251  * implicit back refs. For a tree block created in old transaction, the
254  * back refs conversion.
262  * block's owner tree. In this case, full back refs is used for pointers
263  * in the block. Remove these full back refs, add implicit back refs for
267  * the block's owner tree. In this case, implicit back refs is used for
268  * pointers in the block. Add full back refs for every pointers in the
270  * implicit back refs are entailed to the new block.
273  * not the block's owner tree. Add implicit back refs for every pointer in
279  * The key type is used to differentiate between types of back refs.
281  * of back refs.
289  * The extent ref structure for the implicit back refs has fields for:
296  * The key offset for the implicit back refs is hash of the first
299  * The extent ref structure for the full back refs has field for:
303  * The key offset for the implicit back refs is the first byte of
306  * When a file extent is allocated, The implicit back refs is used.
312  * corresponding implicit back refs and check the following fields:
320  * Both the implicit back refs and the full back refs for tree blocks
321  * only consist of key. The key offset for the implicit back refs is
322  * objectid of block's owner tree. The key offset for the full back refs
325  * When implicit back refs is used, information about the lowest key and
759  * if insert is true and there are too many inline back refs, the path
762  * NOTE: inline back refs are ordered in the same way that back ref
988 	u64 refs;  in setup_inline_extent_backref()  local
1002 	refs = btrfs_extent_refs(leaf, ei);  in setup_inline_extent_backref()
1003 	refs += refs_to_add;  in setup_inline_extent_backref()
1004 	btrfs_set_extent_refs(leaf, ei, refs);  in setup_inline_extent_backref()
1083 	u64 refs;  in update_inline_extent_backref()  local
1086 	refs = btrfs_extent_refs(leaf, ei);  in update_inline_extent_backref()
1087 	if (unlikely(refs_to_mod < 0 && refs + refs_to_mod <= 0)) {  in update_inline_extent_backref()
1099 			  key.objectid, extent_size, refs_to_mod, refs);  in update_inline_extent_backref()
1102 	refs += refs_to_mod;  in update_inline_extent_backref()
1103 	btrfs_set_extent_refs(leaf, ei, refs);  in update_inline_extent_backref()
1117 		refs = btrfs_extent_data_ref_count(leaf, dref);  in update_inline_extent_backref()
1120 		refs = btrfs_shared_data_ref_count(leaf, sref);  in update_inline_extent_backref()
1122 		refs = 1;  in update_inline_extent_backref()
1125 		 * blocks should not have refs > 1.  in update_inline_extent_backref()
1144 	if (unlikely(refs_to_mod < 0 && refs < -refs_to_mod)) {  in update_inline_extent_backref()
1157 			  refs_to_mod, refs);  in update_inline_extent_backref()
1160 	refs += refs_to_mod;  in update_inline_extent_backref()
1162 	if (refs > 0) {  in update_inline_extent_backref()
1164 			btrfs_set_extent_data_ref_count(leaf, dref, refs);  in update_inline_extent_backref()
1166 			btrfs_set_shared_data_ref_count(leaf, sref, refs);  in update_inline_extent_backref()
1198 		 * We're adding refs to a tree block we already own, this  in insert_inline_extent_backref()
1204 "adding refs to an existing tree ref, bytenr %llu num_bytes %llu root_objectid %llu slot %u",  in insert_inline_extent_backref()
1482 	u64 refs;  in __btrfs_inc_extent_ref()  local
1505 	refs = btrfs_extent_refs(leaf, item);  in __btrfs_inc_extent_ref()
1506 	btrfs_set_extent_refs(leaf, item, refs + refs_to_add);  in __btrfs_inc_extent_ref()
1859 	 * We had csum deletions accounted for in our delayed refs rsv, we need  in btrfs_cleanup_ref_head_accounting()
1952 	 * Grab the lock that says we are going to process all the refs for  in btrfs_obtain_ref_head()
2139  * Normally delayed refs get processed in ascending bytenr order. This
2292 		refcount_inc(&head->refs);  in check_delayed_ref()
2394 	/* No inline refs; we need to bail before checking for owner ref. */  in check_committed_ref()
2398 	/* Check for an owner ref; skip over it to the real inline refs. */  in check_committed_ref()
2959 	/* We have inline refs, but not an owner ref. */  in btrfs_get_extent_owner_root()
3013  * Drop one or more refs of @node.
3015  * 1. Locate the extent refs.
3017  *    Locate it, then reduce the refs number or remove the ref line completely.
3019  * 2. Update the refs count in EXTENT/METADATA_ITEM
3026  *		refs 2 gen 6 flags DATA
3042  *		refs 1 gen 6 flags DATA
3050  *		refs 754 gen 6 flags DATA
3067  *		refs 753 gen 6 flags DATA
3090 	u64 refs;  in __btrfs_free_extent()  local
3109 "invalid refs_to_drop, dropping more than 1 refs for tree block %llu refs_to_drop %u",  in __btrfs_free_extent()
3259 	refs = btrfs_extent_refs(leaf, ei);  in __btrfs_free_extent()
3260 	if (refs < refs_to_drop) {  in __btrfs_free_extent()
3262 		"trying to drop %d refs but we only have %llu for bytenr %llu slot %u",  in __btrfs_free_extent()
3263 			       refs_to_drop, refs, bytenr, path->slots[0]);  in __btrfs_free_extent()
3267 	refs -= refs_to_drop;  in __btrfs_free_extent()
3269 	if (refs > 0) {  in __btrfs_free_extent()
3285 			btrfs_set_extent_refs(leaf, ei, refs);  in __btrfs_free_extent()
3305 		/* In this branch refs == 1 */  in __btrfs_free_extent()
3310 		"invalid refs_to_drop, current refs %u refs_to_drop %u slot %u",  in __btrfs_free_extent()
3374  * a given extent, and if there are no other delayed refs to be processed, it
5220 	u64 refs[BTRFS_MAX_LEVEL];  member
5259  * @refs:	the number of refs for wc->level - 1
5273 				  struct extent_buffer *eb, u64 refs, u64 flags, int slot)  in visit_node_for_delete()  argument
5280 	ASSERT(wc->refs[level - 1] > 0);  in visit_node_for_delete()
5294 	 * any refs it's pointing at.  in visit_node_for_delete()
5296 	if (wc->refs[level - 1] == 1)  in visit_node_for_delete()
5334 	u64 refs;  in reada_walk_down()  local
5371 					       wc->level - 1, 1, &refs,  in reada_walk_down()
5379 		 * up with a bogus refs count, if that's the case just skip, if  in reada_walk_down()
5383 		if (refs == 0)  in reada_walk_down()
5387 		if (!visit_node_for_delete(root, wc, eb, refs, flags, slot))  in reada_walk_down()
5400  * back refs for pointers in the block.
5423 	    ((wc->stage == DROP_REFERENCE && wc->refs[level] != 1) ||  in walk_down_proc()
5428 					       &wc->refs[level],  in walk_down_proc()
5433 		if (unlikely(wc->refs[level] == 0)) {  in walk_down_proc()
5441 		if (wc->refs[level] > 1)  in walk_down_proc()
5530 		refcount_inc(&head->refs);  in check_ref_exists()
5630 	 * If we had a drop_progress we need to verify the refs are set as  in maybe_drop_reference()
5650 	    wc->refs[level - 1] > 1) {  in maybe_drop_reference()
5680  * is shared and we need update back refs for the subtree
5705 	 * was created, we know there is no need to update back refs  in do_walk_down()
5724 				       &wc->refs[level - 1],  in do_walk_down()
5730 	if (unlikely(wc->refs[level - 1] == 0)) {  in do_walk_down()
5740 				   wc->refs[level - 1], wc->flags[level - 1],  in do_walk_down()
5749 	if (wc->stage == DROP_REFERENCE && wc->refs[level - 1] > 1) {  in do_walk_down()
5776 	wc->refs[level - 1] = 0;  in do_walk_down()
5836 						       &wc->refs[level],  in walk_up_proc()
5844 			if (unlikely(wc->refs[level] == 0)) {  in walk_up_proc()
5850 			if (wc->refs[level] == 1) {  in walk_up_proc()
5859 	ASSERT(path->locks[level] || wc->refs[level] == 1);  in walk_up_proc()
5861 	if (wc->refs[level] == 1) {  in walk_up_proc()
5902 				    wc->refs[level] == 1);  in walk_up_proc()
5906 	wc->refs[level] = 0;  in walk_up_proc()
5979  * back to DROP_REFERENCE, lookup the current nodes refs and flags, and carry on.
5981  * DROP_REFERENCE. If our refs == 1 then we're going to free this tree block.
6133 						level, 1, &wc->refs[level],  in btrfs_drop_snapshot()
6138 			BUG_ON(wc->refs[level] == 0);  in btrfs_drop_snapshot()
6145 			WARN_ON(wc->refs[level] != 1);  in btrfs_drop_snapshot()
6334 	atomic_inc(&parent->refs);  in btrfs_drop_subtree()
6344 	wc->refs[parent_level] = 1;  in btrfs_drop_subtree()