From f4728ed5307b6be6377b7bdafcab55fd3676a761 Mon Sep 17 00:00:00 2001
From: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
Date: Mon, 17 Jul 2023 16:02:34 +0530
Subject: [PATCH] ieee1275/ofdisk: retry on open and read failure

Sometimes, when booting from a very busy SAN, the access to the
disk can fail and then grub will eventually drop to grub prompt.
This scenario is more frequent when deploying many machines at
the same time using the same SAN.
This patch aims to force the ofdisk module to retry the open or
read function for network disks excluding after it fails. We use
DEFAULT_RETRY_TIMEOUT, which is 15 seconds to specify the time it'll
retry to access the disk before it definitely fails. The timeout can be
changed by setting the environment variable ofdisk_retry_timeout.
If the environment variable fails to read, grub will consider the
default value of 15 seconds.

Signed-off-by: Diego Domingos <diegodo@linux.vnet.ibm.com>
Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
---
 docs/grub.texi                   |  8 ++++
 grub-core/disk/ieee1275/ofdisk.c | 80 +++++++++++++++++++++++++++++++-
 2 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/docs/grub.texi b/docs/grub.texi
index d3f0f6577..c8ebc083d 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -3315,6 +3315,7 @@ These variables have special meaning to GRUB.
 * net_default_ip::
 * net_default_mac::
 * net_default_server::
+* ofdisk_retry_timeout::
 * pager::
 * prefix::
 * pxe_blksize::
@@ -3744,6 +3745,13 @@ The default is the value of @samp{color_normal} (@pxref{color_normal}).
 @xref{Network}.
 
 
+@node ofdisk_retry_timeout
+@subsection ofdisk_retry_timeout
+
+The time in seconds till which the grub will retry to open or read a disk in
+case of failure to do so. This value defaults to 15 seconds.
+
+
 @node pager
 @subsection pager
 
diff --git a/grub-core/disk/ieee1275/ofdisk.c b/grub-core/disk/ieee1275/ofdisk.c
index 7197d5401..f96bbb58c 100644
--- a/grub-core/disk/ieee1275/ofdisk.c
+++ b/grub-core/disk/ieee1275/ofdisk.c
@@ -24,6 +24,9 @@
 #include <grub/ieee1275/ofdisk.h>
 #include <grub/i18n.h>
 #include <grub/time.h>
+#include <grub/env.h>
+
+#define RETRY_DEFAULT_TIMEOUT 15
 
 static char *last_devpath;
 static grub_ieee1275_ihandle_t last_ihandle;
@@ -783,7 +786,7 @@ compute_dev_path (const char *name)
 }
 
 static grub_err_t
-grub_ofdisk_open (const char *name, grub_disk_t disk)
+grub_ofdisk_open_real (const char *name, grub_disk_t disk)
 {
   grub_ieee1275_phandle_t dev;
   char *devpath;
@@ -879,6 +882,56 @@ grub_ofdisk_open (const char *name, grub_disk_t disk)
   return 0;
 }
 
+static grub_uint64_t
+grub_ofdisk_disk_timeout (grub_disk_t disk)
+{
+  grub_uint64_t retry;
+  const char *timeout = grub_env_get ("ofdisk_retry_timeout");
+
+  if (!(grub_strstr (disk->name, "fibre-channel@") ||
+      grub_strstr (disk->name, "vfc-client")) ||
+      grub_strstr(disk->name, "nvme-of"))
+    {
+      /* Do not retry in case of non network drives */
+      return 0;
+    }
+
+  if (timeout != NULL)
+    {
+       retry = grub_strtoul (timeout, 0, 10);
+       if (grub_errno != GRUB_ERR_NONE)
+         {
+           grub_errno = GRUB_ERR_NONE;
+           return RETRY_DEFAULT_TIMEOUT;
+         }
+       if (retry)
+         return retry;
+    }
+  return RETRY_DEFAULT_TIMEOUT;
+}
+
+static grub_err_t
+grub_ofdisk_open (const char *name, grub_disk_t disk)
+{
+  grub_err_t err;
+  grub_uint64_t timeout = grub_get_time_ms () + (grub_ofdisk_disk_timeout (disk) * 1000);
+  _Bool cont;
+  do
+    {
+      err = grub_ofdisk_open_real (name, disk);
+      cont = grub_get_time_ms () < timeout;
+      if (err == GRUB_ERR_UNKNOWN_DEVICE && cont)
+        {
+          grub_dprintf ("ofdisk","Failed to open disk %s. Retrying...\n", name);
+          grub_errno = GRUB_ERR_NONE;
+        }
+      else
+          break;
+      grub_millisleep (1000);
+    } while (cont);
+  return err;
+}
+
 static void
 grub_ofdisk_close (grub_disk_t disk)
 {
@@ -915,7 +968,7 @@ grub_ofdisk_prepare (grub_disk_t disk, grub_disk_addr_t sector)
 }
 
 static grub_err_t
-grub_ofdisk_read (grub_disk_t disk, grub_disk_addr_t sector,
+grub_ofdisk_read_real (grub_disk_t disk, grub_disk_addr_t sector,
 		  grub_size_t size, char *buf)
 {
   grub_err_t err;
@@ -934,6 +987,29 @@ grub_ofdisk_read (grub_disk_t disk, grub_disk_addr_t sector,
   return 0;
 }
 
+static grub_err_t
+grub_ofdisk_read (grub_disk_t disk, grub_disk_addr_t sector,
+		  grub_size_t size, char *buf)
+{
+  grub_err_t err;
+  grub_uint64_t timeout = grub_get_time_ms () + (grub_ofdisk_disk_timeout (disk) * 1000);
+  _Bool cont;
+  do
+    {
+      err = grub_ofdisk_read_real (disk, sector, size, buf);
+      cont = grub_get_time_ms () < timeout;
+      if (err == GRUB_ERR_UNKNOWN_DEVICE && cont)
+        {
+          grub_dprintf ("ofdisk","Failed to read disk %s. Retrying...\n", (char*)disk->data);
+          grub_errno = GRUB_ERR_NONE;
+        }
+      else
+          break;
+      grub_millisleep (1000);
+     } while (cont);
+  return err;
+}
+
 static grub_err_t
 grub_ofdisk_write (grub_disk_t disk, grub_disk_addr_t sector,
 		   grub_size_t size, const char *buf)
-- 
2.41.0