This function calls v9fs_co_close() and v9fs_co_closedir() in a loop. Each
one of the calls adds two thread hops (between main thread and a fs driver
background thread). Each thread hop adds latency, which sums up in
function's loop to a significant duration.

Reduce overall latency by open coding what v9fs_co_close() and
v9fs_co_closedir() do, executing those and the loop itself altogether in
only one background thread block, hence reducing the total amount of
thread hops to only two.

Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
---
 hw/9pfs/9p.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 4f9c2dde9c..4b52b1a22a 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -434,6 +434,7 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu)
     V9fsFidState *f;
     GHashTableIter iter;
     gpointer fid;
+    int err;
 
     /* prevent multiple coroutines running this function simultaniously */
     if (s->reclaiming) {
@@ -446,10 +447,10 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu)
     QSLIST_HEAD(, V9fsFidState) reclaim_list =
         QSLIST_HEAD_INITIALIZER(reclaim_list);
 
+    /* Pick FIDs to be closed, collect them on reclaim_list. */
     while (g_hash_table_iter_next(&iter, &fid, (gpointer *) &f)) {
         /*
-         * Unlink fids cannot be reclaimed. Check
-         * for them and skip them. Also skip fids
+         * Unlinked fids cannot be reclaimed, skip those, and also skip fids
          * currently being operated on.
          */
         if (f->ref || f->flags & FID_NON_RECLAIMABLE) {
@@ -499,17 +500,24 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu)
         }
     }
     /*
-     * Now close the fid in reclaim list. Free them if they
-     * are already clunked.
+     * Close the picked FIDs altogether on a background I/O driver thread. Do
+     * this all at once to keep latency (i.e. amount of thread hops between main
+     * thread <-> fs driver background thread) as low as possible.
      */
+    v9fs_co_run_in_worker({
+        QSLIST_FOREACH(f, &reclaim_list, reclaim_next) {
+            err = (f->fid_type == P9_FID_DIR) ?
+                s->ops->closedir(&s->ctx, &f->fs_reclaim) :
+                s->ops->close(&s->ctx, &f->fs_reclaim);
+            if (!err) {
+                total_open_fd--;
+            }
+        }
+    });
+    /* Free the closed FIDs. */
     while (!QSLIST_EMPTY(&reclaim_list)) {
         f = QSLIST_FIRST(&reclaim_list);
         QSLIST_REMOVE(&reclaim_list, f, V9fsFidState, reclaim_next);
-        if (f->fid_type == P9_FID_FILE) {
-            v9fs_co_close(pdu, &f->fs_reclaim);
-        } else if (f->fid_type == P9_FID_DIR) {
-            v9fs_co_closedir(pdu, &f->fs_reclaim);
-        }
         /*
          * Now drop the fid reference, free it
          * if clunked.
-- 
2.39.5