`> exec` through a mount no longer hangs the editor, and a close holding a last line is answered at once: the line runs at the editor's next step

A shell's truncating open of exec (or look, ctl, log, pager) sends a
setattr that changes nothing; it waited for the editor to be quiet, and
through a 9ns mount that quiet could never come: 9ns answers nothing else
on the mount while the setattr is out, and the editor's step may be out
reading a pane's file through it. This was the "truncating open of exec
hangs, only in selfmount" mystery. Only a truncate of a pane's file or a
tag waits now.

A close holding a last line with no newline hands it to the editor's step
(tree.runClosedLines, beside fillClosedPagers), as a /pager close does, and
is answered at once; a refusal is the log's err.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/fs.zig b/src/fs.zig
index 4a243b10..7a56d387 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -1636,6 +1636,11 @@ pub const Namespace = struct {
     /// a close through a mount may not wait for the editor to be quiet,
     /// as 9ns answers nothing else on that mount while a clunk is out.
     pages: std.ArrayList(struct { serial: u32, bytes: std.ArrayList(u8) }) = .empty,
+    /// The last line each closed open wrote with no newline after it, with
+    /// the node it was written to, for the editor's step to run
+    /// (tree.runClosedLines): a close is answered at once, for the same
+    /// reason as `pages`.
+    closed_lines: std.ArrayList(struct { node: u64, bytes: std.ArrayList(u8) }) = .empty,
     batch: struct {
         serial: u32 = 0,
         node: u64 = 0,
@@ -1685,6 +1690,8 @@ pub const Namespace = struct {
         for (&st.opens) |*o| o.deinit(gpa);
         for (st.pages.items) |*page| page.bytes.deinit(gpa);
         st.pages.deinit(gpa);
+        for (st.closed_lines.items) |*line| line.bytes.deinit(gpa);
+        st.closed_lines.deinit(gpa);
         st.log.deinit(gpa);
         st.out.deinit(gpa);
     }