bcachefs: Debugfs cleanup

This improves flush_buf() so that it always returns nonzero when we're
done reading and ready to return to userspace, and so that it returns
the value we want to return to userspace (number of bytes read, if there
wasn't an error).

In the future we'll be better abstracting this mechanism and pulling it
out of bcachefs, and using it to replace seq_file.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 51 insertions, 64 deletions

diff --git a/fs/bcachefs/debug.c b/fs/bcachefs/debug.c
index 183e9f099ca9..86c4b023ac7c 100644
--- a/fs/bcachefs/debug.c
+++ b/fs/bcachefs/debug.c
@@ -198,7 +198,7 @@ struct dump_iter {
 	ssize_t			ret;	/* bytes read so far */
 };
 
-static int flush_buf(struct dump_iter *i)
+static ssize_t flush_buf(struct dump_iter *i)
 {
 	if (i->buf.pos) {
 		size_t bytes = min_t(size_t, i->buf.pos, i->size);
@@ -214,7 +214,7 @@ static int flush_buf(struct dump_iter *i)
 		memmove(i->buf.buf, i->buf.buf + bytes, i->buf.pos);
 	}
 
-	return 0;
+	return i->size ? 0 : i->ret;
 }
 
 static int bch2_dump_open(struct inode *inode, struct file *file)
@@ -252,7 +252,7 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 	struct btree_trans trans;
 	struct btree_iter iter;
 	struct bkey_s_c k;
-	int err;
+	ssize_t ret;
 
 	i->ubuf = buf;
 	i->size	= size;
@@ -260,14 +260,11 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 
 	bch2_trans_init(&trans, i->c, 0, 0);
 
-	err = for_each_btree_key2(&trans, iter, i->id, i->from,
+	ret = for_each_btree_key2(&trans, iter, i->id, i->from,
 				  BTREE_ITER_PREFETCH|
 				  BTREE_ITER_ALL_SNAPSHOTS, k, ({
-		err = flush_buf(i);
-		if (err)
-			break;
-
-		if (!i->size)
+		ret = flush_buf(i);
+		if (ret)
 			break;
 
 		bch2_bkey_val_to_text(&i->buf, i->c, k);
@@ -276,12 +273,12 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 	}));
 	i->from = iter.pos;
 
-	if (!err)
-		err = flush_buf(i);
+	if (!ret)
+		ret = flush_buf(i);
 
 	bch2_trans_exit(&trans);
 
-	return err ?: i->ret;
+	return ret ?: i->ret;
 }
 
 static const struct file_operations btree_debug_ops = {
@@ -298,43 +295,39 @@ static ssize_t bch2_read_btree_formats(struct file *file, char __user *buf,
 	struct btree_trans trans;
 	struct btree_iter iter;
 	struct btree *b;
-	int err;
+	ssize_t ret;
 
 	i->ubuf = buf;
 	i->size	= size;
 	i->ret	= 0;
 
-	err = flush_buf(i);
-	if (err)
-		return err;
+	ret = flush_buf(i);
+	if (ret)
+		return ret;
 
-	if (!i->size || !bpos_cmp(SPOS_MAX, i->from))
+	if (!bpos_cmp(SPOS_MAX, i->from))
 		return i->ret;
 
 	bch2_trans_init(&trans, i->c, 0, 0);
 
-	for_each_btree_node(&trans, iter, i->id, i->from, 0, b, err) {
-		bch2_btree_node_to_text(&i->buf, i->c, b);
-		err = flush_buf(i);
-		if (err)
+	for_each_btree_node(&trans, iter, i->id, i->from, 0, b, ret) {
+		ret = flush_buf(i);
+		if (ret)
 			break;
 
-		/*
-		 * can't easily correctly restart a btree node traversal across
-		 * all nodes, meh
-		 */
+		bch2_btree_node_to_text(&i->buf, i->c, b);
 		i->from = bpos_cmp(SPOS_MAX, b->key.k.p)
 			? bpos_successor(b->key.k.p)
 			: b->key.k.p;
-
-		if (!i->size)
-			break;
 	}
 	bch2_trans_iter_exit(&trans, &iter);
 
 	bch2_trans_exit(&trans);
 
-	return err < 0 ? err : i->ret;
+	if (!ret)
+		ret = flush_buf(i);
+
+	return ret ?: i->ret;
 }
 
 static const struct file_operations btree_format_debug_ops = {
@@ -351,33 +344,27 @@ static ssize_t bch2_read_bfloat_failed(struct file *file, char __user *buf,
 	struct btree_trans trans;
 	struct btree_iter iter;
 	struct bkey_s_c k;
-	int err;
+	ssize_t ret;
 
 	i->ubuf = buf;
 	i->size	= size;
 	i->ret	= 0;
 
-	err = flush_buf(i);
-	if (err)
-		return err;
-
-	if (!i->size)
-		return i->ret;
+	ret = flush_buf(i);
+	if (ret)
+		return ret;
 
 	bch2_trans_init(&trans, i->c, 0, 0);
 
-	err = for_each_btree_key2(&trans, iter, i->id, i->from,
+	ret = for_each_btree_key2(&trans, iter, i->id, i->from,
 				  BTREE_ITER_PREFETCH|
 				  BTREE_ITER_ALL_SNAPSHOTS, k, ({
 		struct btree_path_level *l = &iter.path->l[0];
 		struct bkey_packed *_k =
 			bch2_btree_node_iter_peek(&l->iter, l->b);
 
-		err = flush_buf(i);
-		if (err)
-			break;
-
-		if (!i->size)
+		ret = flush_buf(i);
+		if (ret)
 			break;
 
 		if (bpos_cmp(l->b->key.k.p, i->prev_node) > 0) {
@@ -390,12 +377,12 @@ static ssize_t bch2_read_bfloat_failed(struct file *file, char __user *buf,
 	}));
 	i->from = iter.pos;
 
-	if (!err)
-		err = flush_buf(i);
-
 	bch2_trans_exit(&trans);
 
-	return err ?: i->ret;
+	if (!ret)
+		ret = flush_buf(i);
+
+	return ret ?: i->ret;
 }
 
 static const struct file_operations bfloat_failed_debug_ops = {
@@ -466,7 +453,7 @@ static ssize_t bch2_cached_btree_nodes_read(struct file *file, char __user *buf,
 	struct dump_iter *i = file->private_data;
 	struct bch_fs *c = i->c;
 	bool done = false;
-	int err;
+	ssize_t ret = 0;
 
 	i->ubuf = buf;
 	i->size	= size;
@@ -477,12 +464,9 @@ static ssize_t bch2_cached_btree_nodes_read(struct file *file, char __user *buf,
 		struct rhash_head *pos;
 		struct btree *b;
 
-		err = flush_buf(i);
-		if (err)
-			return err;
-
-		if (!i->size)
-			break;
+		ret = flush_buf(i);
+		if (ret)
+			return ret;
 
 		rcu_read_lock();
 		i->buf.atomic++;
@@ -500,9 +484,12 @@ static ssize_t bch2_cached_btree_nodes_read(struct file *file, char __user *buf,
 	} while (!done);
 
 	if (i->buf.allocation_failure)
-		return -ENOMEM;
+		ret = -ENOMEM;
 
-	return i->ret;
+	if (!ret)
+		ret = flush_buf(i);
+
+	return ret ?: i->ret;
 }
 
 static const struct file_operations cached_btree_nodes_ops = {
@@ -539,7 +526,7 @@ static ssize_t bch2_btree_transactions_read(struct file *file, char __user *buf,
 	struct dump_iter *i = file->private_data;
 	struct bch_fs *c = i->c;
 	struct btree_trans *trans;
-	int err;
+	ssize_t ret = 0;
 
 	i->ubuf = buf;
 	i->size	= size;
@@ -550,12 +537,9 @@ static ssize_t bch2_btree_transactions_read(struct file *file, char __user *buf,
 		if (trans->task->pid <= i->iter)
 			continue;
 
-		err = flush_buf(i);
-		if (err)
-			return err;
-
-		if (!i->size)
-			break;
+		ret = flush_buf(i);
+		if (ret)
+			return ret;
 
 		bch2_btree_trans_to_text(&i->buf, trans);
 
@@ -571,9 +555,12 @@ static ssize_t bch2_btree_transactions_read(struct file *file, char __user *buf,
 	mutex_unlock(&c->btree_trans_lock);
 
 	if (i->buf.allocation_failure)
-		return -ENOMEM;
+		ret = -ENOMEM;
 
-	return i->ret;
+	if (!ret)
+		ret = flush_buf(i);
+
+	return ret ?: i->ret;
 }
 
 static const struct file_operations btree_transactions_ops = {