On Fri, Aug 8, 2025 at 11:52 AM Pratyush Yadav [off-list ref] wrote:

On Fri, Aug 08 2025, Pratyush Yadav wrote:
[...]

quoted

quoted

@@ -144,14 +144,35 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
                             unsigned int order)
 {
     struct kho_mem_phys_bits *bits;
-    struct kho_mem_phys *physxa;
+    struct kho_mem_phys *physxa, *new_physxa;
     const unsigned long pfn_high = pfn >> order;

     might_sleep();

-    physxa = xa_load_or_alloc(&track->orders, order, sizeof(*physxa));
-    if (IS_ERR(physxa))
-            return PTR_ERR(physxa);
+    physxa = xa_load(&track->orders, order);
+    if (!physxa) {
+            new_physxa = kzalloc(sizeof(*physxa), GFP_KERNEL);
+            if (!new_physxa)
+                    return -ENOMEM;
+
+            xa_init(&new_physxa->phys_bits);
+            physxa = xa_cmpxchg(&track->orders, order, NULL, new_physxa,
+                                GFP_KERNEL);
+            if (xa_is_err(physxa)) {
+                    int err = xa_err(physxa);
+
+                    xa_destroy(&new_physxa->phys_bits);
+                    kfree(new_physxa);
+
+                    return err;
+            }
+            if (physxa) {
+                    xa_destroy(&new_physxa->phys_bits);
+                    kfree(new_physxa);
+            } else {
+                    physxa = new_physxa;
+            }

I suppose this could be simplified a bit to:

      err = xa_err(physxa);
        if (err || physxa) {
              xa_destroy(&new_physxa->phys_bits);
                kfree(new_physxa);

              if (err)
                      return err;
      } else {
              physxa = new_physxa;
      }

My email client completely messed the whitespace up so this is a bit
unreadable. Here is what I meant:

        err = xa_err(physxa);
        if (err || physxa) {
                xa_destroy(&new_physxa->phys_bits);
                kfree(new_physxa);

                if (err)
                        return err;
        } else {
                physxa = new_physxa;
        }

[...]

Thanks Pratyush, I will make this simplification change if Andrew does
not take this patch in before the next revision.

Pasha