btrfs: move btrfs_realloc_node() from ctree.c into defrag.c

btrfs_realloc_node() is only used by the defrag code. Nowadays we have a
defrag.c file, so move it, and its helper close_blocks(), into defrag.c.

During the move also do a few minor cosmetic changes:

1) Change the return value of close_blocks() from int to bool;

2) Use SZ_32K instead of 32768 at close_blocks();

3) Make some variables const in btrfs_realloc_node(), 'blocksize' and
   'end_slot';

4) Get rid of 'parent_nritems' variable, in both places where it was
   used it could be replaced by calling btrfs_header_nritems(parent);

5) Change the type of a couple variables from int to bool;

6) Rename variable 'err' to 'ret', as that's the most common name we
   use to track the return value of a function;

7) Move some variables from the top scope to the scope of the for loop
   where they are used.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.c

@@ -736,19 +736,6 @@ int btrfs_cow_block(struct btrfs_trans_handle *trans,
 }
 ALLOW_ERROR_INJECTION(btrfs_cow_block, ERRNO);
 
-/*
- * helper function for defrag to decide if two blocks pointed to by a
- * node are actually close by
- */
-static int close_blocks(u64 blocknr, u64 other, u32 blocksize)
-{
-	if (blocknr < other && other - (blocknr + blocksize) < 32768)
-		return 1;
-	if (blocknr > other && blocknr - (other + blocksize) < 32768)
-		return 1;
-	return 0;
-}
-
 /*
  * same as comp_keys only with two btrfs_key's
  */
@@ -769,105 +756,6 @@ int __pure btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_ke
 	return 0;
 }
 
-/*
- * this is used by the defrag code to go through all the
- * leaves pointed to by a node and reallocate them so that
- * disk order is close to key order
- */
-int btrfs_realloc_node(struct btrfs_trans_handle *trans,
-		       struct btrfs_root *root, struct extent_buffer *parent,
-		       int start_slot, u64 *last_ret,
-		       struct btrfs_key *progress)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct extent_buffer *cur;
-	u64 blocknr;
-	u64 search_start = *last_ret;
-	u64 last_block = 0;
-	u64 other;
-	u32 parent_nritems;
-	int end_slot;
-	int i;
-	int err = 0;
-	u32 blocksize;
-	int progress_passed = 0;
-	struct btrfs_disk_key disk_key;
-
-	/*
-	 * COWing must happen through a running transaction, which always
-	 * matches the current fs generation (it's a transaction with a state
-	 * less than TRANS_STATE_UNBLOCKED). If it doesn't, then turn the fs
-	 * into error state to prevent the commit of any transaction.
-	 */
-	if (unlikely(trans->transaction != fs_info->running_transaction ||
-		     trans->transid != fs_info->generation)) {
-		btrfs_abort_transaction(trans, -EUCLEAN);
-		btrfs_crit(fs_info,
-"unexpected transaction when attempting to reallocate parent %llu for root %llu, transaction %llu running transaction %llu fs generation %llu",
-			   parent->start, btrfs_root_id(root), trans->transid,
-			   fs_info->running_transaction->transid,
-			   fs_info->generation);
-		return -EUCLEAN;
-	}
-
-	parent_nritems = btrfs_header_nritems(parent);
-	blocksize = fs_info->nodesize;
-	end_slot = parent_nritems - 1;
-
-	if (parent_nritems <= 1)
-		return 0;
-
-	for (i = start_slot; i <= end_slot; i++) {
-		int close = 1;
-
-		btrfs_node_key(parent, &disk_key, i);
-		if (!progress_passed && btrfs_comp_keys(&disk_key, progress) < 0)
-			continue;
-
-		progress_passed = 1;
-		blocknr = btrfs_node_blockptr(parent, i);
-		if (last_block == 0)
-			last_block = blocknr;
-
-		if (i > 0) {
-			other = btrfs_node_blockptr(parent, i - 1);
-			close = close_blocks(blocknr, other, blocksize);
-		}
-		if (!close && i < end_slot) {
-			other = btrfs_node_blockptr(parent, i + 1);
-			close = close_blocks(blocknr, other, blocksize);
-		}
-		if (close) {
-			last_block = blocknr;
-			continue;
-		}
-
-		cur = btrfs_read_node_slot(parent, i);
-		if (IS_ERR(cur))
-			return PTR_ERR(cur);
-		if (search_start == 0)
-			search_start = last_block;
-
-		btrfs_tree_lock(cur);
-		err = btrfs_force_cow_block(trans, root, cur, parent, i,
-					    &cur, search_start,
-					    min(16 * blocksize,
-						(end_slot - i) * blocksize),
-					    BTRFS_NESTING_COW);
-		if (err) {
-			btrfs_tree_unlock(cur);
-			free_extent_buffer(cur);
-			break;
-		}
-		search_start = cur->start;
-		last_block = cur->start;
-		*last_ret = search_start;
-		btrfs_tree_unlock(cur);
-		free_extent_buffer(cur);
-	}
-	return err;
-}
-
 /*
  * Search for a key in the given extent_buffer.
  *

fs/btrfs/ctree.h

@@ -557,10 +557,6 @@ int btrfs_search_slot_for_read(struct btrfs_root *root,
 			       const struct btrfs_key *key,
 			       struct btrfs_path *p, int find_higher,
 			       int return_any);
-int btrfs_realloc_node(struct btrfs_trans_handle *trans,
-		       struct btrfs_root *root, struct extent_buffer *parent,
-		       int start_slot, u64 *last_ret,
-		       struct btrfs_key *progress);
 void btrfs_release_path(struct btrfs_path *p);
 struct btrfs_path *btrfs_alloc_path(void);
 void btrfs_free_path(struct btrfs_path *p);

fs/btrfs/defrag.c

@@ -337,6 +337,111 @@ int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
 	return 0;
 }
 
+/*
+ * Check if two blocks addresses are close, used by defrag.
+ */
+static bool close_blocks(u64 blocknr, u64 other, u32 blocksize)
+{
+	if (blocknr < other && other - (blocknr + blocksize) < SZ_32K)
+		return true;
+	if (blocknr > other && blocknr - (other + blocksize) < SZ_32K)
+		return true;
+	return false;
+}
+
+/*
+ * Go through all the leaves pointed to by a node and reallocate them so that
+ * disk order is close to key order.
+ */
+static int btrfs_realloc_node(struct btrfs_trans_handle *trans,
+			      struct btrfs_root *root,
+			      struct extent_buffer *parent,
+			      int start_slot, u64 *last_ret,
+			      struct btrfs_key *progress)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	const u32 blocksize = fs_info->nodesize;
+	const int end_slot = btrfs_header_nritems(parent) - 1;
+	u64 search_start = *last_ret;
+	u64 last_block = 0;
+	int ret = 0;
+	bool progress_passed = false;
+
+	/*
+	 * COWing must happen through a running transaction, which always
+	 * matches the current fs generation (it's a transaction with a state
+	 * less than TRANS_STATE_UNBLOCKED). If it doesn't, then turn the fs
+	 * into error state to prevent the commit of any transaction.
+	 */
+	if (unlikely(trans->transaction != fs_info->running_transaction ||
+		     trans->transid != fs_info->generation)) {
+		btrfs_abort_transaction(trans, -EUCLEAN);
+		btrfs_crit(fs_info,
+"unexpected transaction when attempting to reallocate parent %llu for root %llu, transaction %llu running transaction %llu fs generation %llu",
+			   parent->start, btrfs_root_id(root), trans->transid,
+			   fs_info->running_transaction->transid,
+			   fs_info->generation);
+		return -EUCLEAN;
+	}
+
+	if (btrfs_header_nritems(parent) <= 1)
+		return 0;
+
+	for (int i = start_slot; i <= end_slot; i++) {
+		struct extent_buffer *cur;
+		struct btrfs_disk_key disk_key;
+		u64 blocknr;
+		u64 other;
+		bool close = true;
+
+		btrfs_node_key(parent, &disk_key, i);
+		if (!progress_passed && btrfs_comp_keys(&disk_key, progress) < 0)
+			continue;
+
+		progress_passed = true;
+		blocknr = btrfs_node_blockptr(parent, i);
+		if (last_block == 0)
+			last_block = blocknr;
+
+		if (i > 0) {
+			other = btrfs_node_blockptr(parent, i - 1);
+			close = close_blocks(blocknr, other, blocksize);
+		}
+		if (!close && i < end_slot) {
+			other = btrfs_node_blockptr(parent, i + 1);
+			close = close_blocks(blocknr, other, blocksize);
+		}
+		if (close) {
+			last_block = blocknr;
+			continue;
+		}
+
+		cur = btrfs_read_node_slot(parent, i);
+		if (IS_ERR(cur))
+			return PTR_ERR(cur);
+		if (search_start == 0)
+			search_start = last_block;
+
+		btrfs_tree_lock(cur);
+		ret = btrfs_force_cow_block(trans, root, cur, parent, i,
+					    &cur, search_start,
+					    min(16 * blocksize,
+						(end_slot - i) * blocksize),
+					    BTRFS_NESTING_COW);
+		if (ret) {
+			btrfs_tree_unlock(cur);
+			free_extent_buffer(cur);
+			break;
+		}
+		search_start = cur->start;
+		last_block = cur->start;
+		*last_ret = search_start;
+		btrfs_tree_unlock(cur);
+		free_extent_buffer(cur);
+	}
+	return ret;
+}
+
 /*
  * Defrag all the leaves in a given btree.
  * Read all the leaves and try to get key order to