[PATCH V2] ieee1275/ofdisk: retry on open and read failure

[Mukesh Kumar Chaurasiya]

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 after it fails. We use DEFAULT_RETRY_TIMEOUT, which
is 15000ms or 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.

Signed-off-by: Diego Domingos <diegodo@linux.vnet.ibm.com>
Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.vnet.ibm.com>
---
 grub-core/disk/ieee1275/ofdisk.c | 65 +++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/grub-core/disk/ieee1275/ofdisk.c b/grub-core/disk/ieee1275/ofdisk.c
index c6cba0c8a..f4183a531 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 15000
 
 static char *last_devpath;
 static grub_ieee1275_ihandle_t last_ihandle;
@@ -452,7 +455,7 @@ 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;
@@ -525,6 +528,41 @@ grub_ofdisk_open (const char *name, grub_disk_t disk)
   return 0;
 }
 
+static grub_uint64_t
+grub_ofdisk_disk_timeout(void)
+{
+   if(grub_env_get("ofdisk_retry_timeout") != NULL)
+     {
+       grub_uint64_t retry = 
grub_strtoul(grub_env_get("ofdisk_retry_timeout"), 0, 10);
+       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();
+
+ retry:
+  err = grub_ofdisk_open_real (name, disk);
+
+  if (err == GRUB_ERR_UNKNOWN_DEVICE)
+    {
+      if (grub_get_time_ms () < timeout)
+        {
+          grub_dprintf ("ofdisk","Failed to open disk %s. Retrying...\n", 
name);
+          grub_errno = GRUB_ERR_NONE;
+          goto retry;
+       }
+    }
+
+  return err;
+}
+
 static void
 grub_ofdisk_close (grub_disk_t disk)
 {
@@ -568,7 +606,7 @@ 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;
@@ -587,6 +625,29 @@ 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();
+
+ retry:
+  err = grub_ofdisk_read_real (disk, sector, size, buf);
+
+  if (err == GRUB_ERR_READ_ERROR)
+    {
+      if (grub_get_time_ms () < timeout)
+        {
+          grub_dprintf ("ofdisk","Failed to read disk %s. Retrying...\n", 
(char*)disk->data);
+          grub_errno = GRUB_ERR_NONE;
+          goto retry;
+       }
+    }
+
+  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)
-- 
2.31.1