1 files changed, 46 insertions, 6 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index b39b339fbf96..dcb510f38dda 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -114,6 +114,22 @@ noinline void btrfs_release_path(struct btrfs_path *p)
 }
 
 /*
+ * We want the transaction abort to print stack trace only for errors where the
+ * cause could be a bug, eg. due to ENOSPC, and not for common errors that are
+ * caused by external factors.
+ */
+bool __cold abort_should_print_stack(int errno)
+{
+	switch (errno) {
+	case -EIO:
+	case -EROFS:
+	case -ENOMEM:
+		return false;
+	}
+	return true;
+}
+
+/*
  * safely gets a reference on the root node of a tree.  A lock
  * is not taken, so a concurrent writer may put a different node
  * at the root of the tree.  See btrfs_lock_root_node for the
@@ -4647,7 +4663,12 @@ int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
 	int ret;
 	int i;
 
-	ASSERT(!path->nowait);
+	/*
+	 * The nowait semantics are used only for write paths, where we don't
+	 * use the tree mod log and sequence numbers.
+	 */
+	if (time_seq)
+		ASSERT(!path->nowait);
 
 	nritems = btrfs_header_nritems(path->nodes[0]);
 	if (nritems == 0)
@@ -4667,7 +4688,14 @@ again:
 		if (path->need_commit_sem) {
 			path->need_commit_sem = 0;
 			need_commit_sem = true;
-			down_read(&fs_info->commit_root_sem);
+			if (path->nowait) {
+				if (!down_read_trylock(&fs_info->commit_root_sem)) {
+					ret = -EAGAIN;
+					goto done;
+				}
+			} else {
+				down_read(&fs_info->commit_root_sem);
+			}
 		}
 		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 	}
@@ -4743,7 +4771,7 @@ again:
 		next = c;
 		ret = read_block_for_search(root, path, &next, level,
 					    slot, &key);
-		if (ret == -EAGAIN)
+		if (ret == -EAGAIN && !path->nowait)
 			goto again;
 
 		if (ret < 0) {
@@ -4753,6 +4781,10 @@ again:
 
 		if (!path->skip_locking) {
 			ret = btrfs_try_tree_read_lock(next);
+			if (!ret && path->nowait) {
+				ret = -EAGAIN;
+				goto done;
+			}
 			if (!ret && time_seq) {
 				/*
 				 * If we don't get the lock, we may be racing
@@ -4783,7 +4815,7 @@ again:
 
 		ret = read_block_for_search(root, path, &next, level,
 					    0, &key);
-		if (ret == -EAGAIN)
+		if (ret == -EAGAIN && !path->nowait)
 			goto again;
 
 		if (ret < 0) {
@@ -4791,8 +4823,16 @@ again:
 			goto done;
 		}
 
-		if (!path->skip_locking)
-			btrfs_tree_read_lock(next);
+		if (!path->skip_locking) {
+			if (path->nowait) {
+				if (!btrfs_try_tree_read_lock(next)) {
+					ret = -EAGAIN;
+					goto done;
+				}
+			} else {
+				btrfs_tree_read_lock(next);
+			}
+		}
 	}
 	ret = 0;
 done: