zfs: fix patch inclusion

modules/zfs.nix

@@ -20,10 +20,19 @@ let
   arcMaxBytes = (totalRamBytes - totalHugepageBytes) * 60 / 100;
 in
 {
-  # remove inline dbuf_evict_one call so the dedicated eviction thread
+  # Patch ZFS: remove inline dbuf_evict_one from dbuf_evict_notify.
-  # handles cache pressure instead of stalling txg_sync on 6.14+.
   # https://github.com/openzfs/zfs/issues/18426
-  boot.zfs.package = pkgs.zfs_2_4.overrideAttrs (old: {
+  #
+  # boot.zfs.package = userspace (zfs, zpool commands)
+  # boot.zfs.modulePackage = kernel module (zfs.ko, spl.ko)
+  # Both must be patched. The kernel module is built separately
+  # from boot.kernelPackages.zfs_2_3, which we override here.
+  boot.zfs.package = pkgs.zfs.overrideAttrs (old: {
+    patches = (old.patches or [ ]) ++ [
+      ../patches/zfs/0001-remove-dbuf_evict_one-call.patch
+    ];
+  });
+  boot.zfs.modulePackage = config.boot.kernelPackages.zfs_2_3.overrideAttrs (old: {
     patches = (old.patches or [ ]) ++ [
       ../patches/zfs/0001-remove-dbuf_evict_one-call.patch
     ];