btrfs: turn fs_roots_radix in btrfs_fs_info into an XArray

… rename it to simply fs_roots and adjust all usages of this object to use
the XArray API, because it is notionally easier to use and understand, as
it provides array semantics, and also takes care of locking for us,
further simplifying the code.

Also do some refactoring, esp. where the API change requires largely
rewriting some functions, anyway.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 49 insertions, 63 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 875b801ab3d7..06c0a958d114 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -23,7 +23,7 @@
 #include "space-info.h"
 #include "zoned.h"
 
-#define BTRFS_ROOT_TRANS_TAG 0
+#define BTRFS_ROOT_TRANS_TAG				XA_MARK_0
 
 /*
  * Transaction states and transitions
@@ -437,15 +437,15 @@ static int record_root_in_trans(struct btrfs_trans_handle *trans,
 		 */
 		smp_wmb();
 
-		spin_lock(&fs_info->fs_roots_radix_lock);
+		spin_lock(&fs_info->fs_roots_lock);
 		if (root->last_trans == trans->transid && !force) {
-			spin_unlock(&fs_info->fs_roots_radix_lock);
+			spin_unlock(&fs_info->fs_roots_lock);
 			return 0;
 		}
-		radix_tree_tag_set(&fs_info->fs_roots_radix,
-				   (unsigned long)root->root_key.objectid,
-				   BTRFS_ROOT_TRANS_TAG);
-		spin_unlock(&fs_info->fs_roots_radix_lock);
+		xa_set_mark(&fs_info->fs_roots,
+			    (unsigned long)root->root_key.objectid,
+			    BTRFS_ROOT_TRANS_TAG);
+		spin_unlock(&fs_info->fs_roots_lock);
 		root->last_trans = trans->transid;
 
 		/* this is pretty tricky.  We don't want to
@@ -487,11 +487,9 @@ void btrfs_add_dropped_root(struct btrfs_trans_handle *trans,
 	spin_unlock(&cur_trans->dropped_roots_lock);
 
 	/* Make sure we don't try to update the root at commit time */
-	spin_lock(&fs_info->fs_roots_radix_lock);
-	radix_tree_tag_clear(&fs_info->fs_roots_radix,
-			     (unsigned long)root->root_key.objectid,
-			     BTRFS_ROOT_TRANS_TAG);
-	spin_unlock(&fs_info->fs_roots_radix_lock);
+	xa_clear_mark(&fs_info->fs_roots,
+		      (unsigned long)root->root_key.objectid,
+		      BTRFS_ROOT_TRANS_TAG);
 }
 
 int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
@@ -1404,9 +1402,8 @@ void btrfs_add_dead_root(struct btrfs_root *root)
 static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_root *gang[8];
-	int i;
-	int ret;
+	struct btrfs_root *root;
+	unsigned long index;
 
 	/*
 	 * At this point no one can be using this transaction to modify any tree
@@ -1414,57 +1411,46 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
 	 */
 	ASSERT(trans->transaction->state == TRANS_STATE_COMMIT_DOING);
 
-	spin_lock(&fs_info->fs_roots_radix_lock);
-	while (1) {
-		ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
-						 (void **)gang, 0,
-						 ARRAY_SIZE(gang),
-						 BTRFS_ROOT_TRANS_TAG);
-		if (ret == 0)
-			break;
-		for (i = 0; i < ret; i++) {
-			struct btrfs_root *root = gang[i];
-			int ret2;
-
-			/*
-			 * At this point we can neither have tasks logging inodes
-			 * from a root nor trying to commit a log tree.
-			 */
-			ASSERT(atomic_read(&root->log_writers) == 0);
-			ASSERT(atomic_read(&root->log_commit[0]) == 0);
-			ASSERT(atomic_read(&root->log_commit[1]) == 0);
-
-			radix_tree_tag_clear(&fs_info->fs_roots_radix,
-					(unsigned long)root->root_key.objectid,
-					BTRFS_ROOT_TRANS_TAG);
-			spin_unlock(&fs_info->fs_roots_radix_lock);
-
-			btrfs_free_log(trans, root);
-			ret2 = btrfs_update_reloc_root(trans, root);
-			if (ret2)
-				return ret2;
-
-			/* see comments in should_cow_block() */
-			clear_bit(BTRFS_ROOT_FORCE_COW, &root->state);
-			smp_mb__after_atomic();
-
-			if (root->commit_root != root->node) {
-				list_add_tail(&root->dirty_list,
-					&trans->transaction->switch_commits);
-				btrfs_set_root_node(&root->root_item,
-						    root->node);
-			}
+	spin_lock(&fs_info->fs_roots_lock);
+	xa_for_each_marked(&fs_info->fs_roots, index, root, BTRFS_ROOT_TRANS_TAG) {
+		int ret;
+
+		/*
+		 * At this point we can neither have tasks logging inodes
+		 * from a root nor trying to commit a log tree.
+		 */
+		ASSERT(atomic_read(&root->log_writers) == 0);
+		ASSERT(atomic_read(&root->log_commit[0]) == 0);
+		ASSERT(atomic_read(&root->log_commit[1]) == 0);
+
+		xa_clear_mark(&fs_info->fs_roots,
+			      (unsigned long)root->root_key.objectid,
+			      BTRFS_ROOT_TRANS_TAG);
+		spin_unlock(&fs_info->fs_roots_lock);
 
-			ret2 = btrfs_update_root(trans, fs_info->tree_root,
-						&root->root_key,
-						&root->root_item);
-			if (ret2)
-				return ret2;
-			spin_lock(&fs_info->fs_roots_radix_lock);
-			btrfs_qgroup_free_meta_all_pertrans(root);
+		btrfs_free_log(trans, root);
+		ret = btrfs_update_reloc_root(trans, root);
+		if (ret)
+			return ret;
+
+		/* See comments in should_cow_block() */
+		clear_bit(BTRFS_ROOT_FORCE_COW, &root->state);
+		smp_mb__after_atomic();
+
+		if (root->commit_root != root->node) {
+			list_add_tail(&root->dirty_list,
+				      &trans->transaction->switch_commits);
+			btrfs_set_root_node(&root->root_item, root->node);
 		}
+
+		ret = btrfs_update_root(trans, fs_info->tree_root,
+					&root->root_key, &root->root_item);
+		if (ret)
+			return ret;
+		spin_lock(&fs_info->fs_roots_lock);
+		btrfs_qgroup_free_meta_all_pertrans(root);
 	}
-	spin_unlock(&fs_info->fs_roots_radix_lock);
+	spin_unlock(&fs_info->fs_roots_lock);
 	return 0;
 }