grub2/0001-ofdisk-enhance-boot-time-by-focusing-on-boot-disk-re.patch

From b353ca96bf002a9262fdf74637f39615d003d069 Mon Sep 17 00:00:00 2001
From: Michael Chang <mchang@suse.com>
Date: Fri, 8 Dec 2023 11:51:57 +0800
Subject: [PATCH 1/2] ofdisk: enhance boot time by focusing on boot disk
 relevance

After a historical review, it's clear that a boot delay regression
coincided with the introduction of the fcp iterating patch. Reverting
this patch has shown promising signs in mitigating the issue. In order
to improve the efficiency, a more refined discovery process is proposed,
aiming to exclude device types differing from the boot disk to curtail
unnecessary iterations.

This patch extends prior efforts by exclusively targeting root device
discovery linked to the boot disk, verifying device types to prevent
process elongation.

It is worth noting that grub's opportunistic approach to assembling the
root device, seeking accessible results in parallel during iteration,
sometimes allows even a partially assembled RAID, albeit in a degraded
mode. However, delays stem from unrelated devices appearing before the
actual boot device.

To streamline the boot process, the patch utilizes parent nodes in
conjunction with block device nodes to extract essential boot-related
information. This refined identification method efficiently limits the
application's scope to devices connected to the chosen boot device,
notably optimizing subsequent device iteration. By adeptly filtering out
devices not linked to the same FCP (Fibre Channel Protocol) device, it
significantly enhances boot efficiency, ensuring a more streamlined and
efficient boot process.

Signed-off-by: Michael Chang <mchang@suse.com>
---
 grub-core/disk/ieee1275/ofdisk.c | 136 +++++++++++++++++++++++++++++--
 1 file changed, 131 insertions(+), 5 deletions(-)

--- a/grub-core/disk/ieee1275/ofdisk.c
+++ b/grub-core/disk/ieee1275/ofdisk.c
@@ -31,6 +31,13 @@
 static char *last_devpath;
 static grub_ieee1275_ihandle_t last_ihandle;
 
+#define IEEE1275_DISK_ALIAS "/disk@"
+#define IEEE1275_NVMEOF_DISK_ALIAS "/nvme-of/controller@"
+
+static char *boot_type;
+static char *boot_parent;
+static int is_boot_nvmeof;
+
 struct ofdisk_hash_ent
 {
   char *devpath;
@@ -529,12 +536,21 @@
 {
   if (grub_strcmp (alias->type, "fcp") == 0)
   {
-      // Iterate disks
-      dev_iterate_fcp_disks(alias);
-    
-      // Iterate NVMeoF
-      dev_iterate_fcp_nvmeof(alias);
+    if (boot_type &&
+	grub_strcmp (boot_type, alias->type) != 0)
+      {
+	grub_dprintf ("ofdisk", "Skipped device: %s, type %s did not match boot_type %s\n",
+	    alias->path, alias->type, boot_type);
+	goto iter_children;
+      }
 
+    if (grub_strcmp (boot_parent, alias->path) == 0)
+      {
+	if (is_boot_nvmeof)
+	  dev_iterate_fcp_nvmeof(alias);
+	else
+	  dev_iterate_fcp_disks(alias);
+      }
   }
   else if (grub_strcmp (alias->type, "vscsi") == 0)
     {
@@ -552,6 +568,14 @@
       char *buf, *bufptr;
       unsigned i;
 
+      if (boot_type &&
+	  grub_strcmp (boot_type, alias->type) != 0)
+	{
+	  grub_dprintf ("ofdisk", "Skipped device: %s, type %s did not match boot_type %s\n",
+	      alias->path, alias->type, boot_type);
+	  return;
+	}
+
       if (grub_ieee1275_open (alias->path, &ihandle))
 	return;
 
@@ -615,6 +639,14 @@
       grub_uint16_t table_size;
       grub_ieee1275_ihandle_t ihandle;
 
+      if (boot_type &&
+	  grub_strcmp (boot_type, alias->type) != 0)
+	{
+	  grub_dprintf ("ofdisk", "Skipped device: %s, type %s did not match boot_type %s\n",
+	      alias->path, alias->type, boot_type);
+	  goto iter_children;
+	}
+
       buf = grub_malloc (grub_strlen (alias->path) +
                          sizeof ("/disk@7766554433221100"));
       if (!buf)
@@ -674,6 +706,7 @@
       return;
     }
 
+ iter_children:
   {
     struct grub_ieee1275_devalias child;
 
@@ -1046,6 +1079,68 @@
     .next = 0
   };
 
+static char *
+get_parent_devname (const char *devname, int *is_nvmeof)
+{
+  char *parent, *pptr;
+
+  if (is_nvmeof)
+    *is_nvmeof = 0;
+
+  parent = grub_strdup (devname);
+
+  if (parent == NULL)
+    {
+      grub_print_error ();
+      return NULL;
+    }
+
+  pptr = grub_strstr (parent, IEEE1275_DISK_ALIAS);
+
+  if (pptr != NULL)
+    {
+      *pptr = '\0';
+      return parent;
+    }
+
+  pptr = grub_strstr (parent, IEEE1275_NVMEOF_DISK_ALIAS);
+
+  if (pptr != NULL)
+    {
+      *pptr = '\0';
+      if (is_nvmeof)
+	*is_nvmeof = 1;
+      return parent;
+    }
+
+  return parent;
+}
+
+static char *
+get_boot_device_parent (const char *bootpath, int *is_nvmeof)
+{
+  char *dev, *canon, *parent;
+
+  dev = grub_ieee1275_get_aliasdevname (bootpath);
+  canon = grub_ieee1275_canonicalise_devname (dev);
+
+  if (!canon)
+    {
+      /* This should not happen. */
+      grub_error (GRUB_ERR_BAD_DEVICE, "canonicalise devname failed");
+      grub_print_error ();
+      return NULL;
+    }
+  else
+    grub_dprintf ("ofdisk", "%s is canonical %s\n", bootpath, canon);
+
+  parent = get_parent_devname (canon, is_nvmeof);
+  grub_dprintf ("ofdisk", "%s is parent of %s\n", parent, canon);
+
+  grub_free (canon);
+  return parent;
+}
+
 static void
 insert_bootpath (void)
 {
@@ -1081,6 +1176,12 @@
       char *device = grub_ieee1275_get_devname (bootpath);
       op = ofdisk_hash_add (device, NULL);
       op->is_boot = 1;
+      boot_parent = get_boot_device_parent (bootpath, &is_boot_nvmeof);
+      boot_type =  grub_ieee1275_get_device_type (boot_parent);
+      if (boot_type)
+	grub_dprintf ("ofdisk", "the boot device type %s is used for root device discovery, others excluded\n", boot_type);
+      else
+	grub_dprintf ("ofdisk", "unknown boot device type, will use all devices to discover root and may be slow\n");
     }
   grub_free (type);
   grub_free (bootpath);
@@ -1097,12 +1198,37 @@
   grub_disk_dev_unregister (&grub_ofdisk_dev);
 }
 
+static const char *
+grub_env_get_boot_type (struct grub_env_var *var __attribute__ ((unused)),
+			const char *val __attribute__ ((unused)))
+{
+  static char *ret;
+
+  if (!ret)
+    ret = grub_xasprintf("boot: %s type: %s is_nvmeof: %d",
+	      boot_parent,
+	      boot_type ? : "unknown",
+	      is_boot_nvmeof);
+
+  return ret;
+}
+
+static char *
+grub_env_set_boot_type (struct grub_env_var *var __attribute__ ((unused)),
+			const char *val __attribute__ ((unused)))
+{
+  /* READ ONLY */
+  return NULL;
+}
+
 void
 grub_ofdisk_init (void)
 {
   grub_disk_firmware_fini = grub_ofdisk_fini;
 
   insert_bootpath ();
+  grub_register_variable_hook ("ofdisk_boot_type", grub_env_get_boot_type,
+                               grub_env_set_boot_type );
 
   grub_disk_dev_register (&grub_ofdisk_dev);
 }