[PATCH] ieee1275: Avoiding many unecessary open/close

[Diego Domingos]

This patch aims to change the grub_ofdisk_open and grub_ofdisk_close behaviors. 
Since some devices (Fibre Channel and NVMe) can have a long time for shutdown 
notification, we should avoid open and close the disks as much as we can.

So, we are changing how those functions works. The grub_ofdisk_close will take 
care of just changing the disk element status, by doing a soft close, i.e, the 
firmware will not be called. On the other hand, the grub_ofdisk_open will take 
care of closing the current disk opened only if the disk requested in the 
current call is different from the current one. This close will be responsible 
to request the firmware to actually close the disk.

Yet, this patch modifies the grub_ofdisk_get_block_size function, avoiding open 
and close calls inside of it.

Thank you Michael Chang (mchang@suse.com) for all support.

Signed-off-by: Diego Domingos <diegodo@linux.vnet.ibm.com>
---
 grub-core/disk/ieee1275/ofdisk.c | 64 +++++++++++++++++---------------
 1 file changed, 35 insertions(+), 29 deletions(-)

diff --git a/grub-core/disk/ieee1275/ofdisk.c b/grub-core/disk/ieee1275/ofdisk.c
index d887d4b..f3a6ecd 100644
--- a/grub-core/disk/ieee1275/ofdisk.c
+++ b/grub-core/disk/ieee1275/ofdisk.c
@@ -44,7 +44,7 @@ struct ofdisk_hash_ent
 };
 
 static grub_err_t
-grub_ofdisk_get_block_size (const char *device, grub_uint32_t *block_size,
+grub_ofdisk_get_block_size (grub_uint32_t *block_size,
                            struct ofdisk_hash_ent *op);
 
 #define OFDISK_HASH_SZ 8
@@ -461,6 +461,7 @@ grub_ofdisk_open (const char *name, grub_disk_t disk)
   grub_ssize_t actual;
   grub_uint32_t block_size = 0;
   grub_err_t err;
+  struct ofdisk_hash_ent *op;
 
   if (grub_strncmp (name, "ieee1275/", sizeof ("ieee1275/") - 1) != 0)
       return grub_error (GRUB_ERR_UNKNOWN_DEVICE,
@@ -471,6 +472,35 @@ grub_ofdisk_open (const char *name, grub_disk_t disk)
 
   grub_dprintf ("disk", "Opening `%s'.\n", devpath);
 
+  op = ofdisk_hash_find (devpath);
+  if (!op)
+    op = ofdisk_hash_add (devpath, NULL);
+  if (!op)
+    {
+      grub_free (devpath);
+      return grub_errno;
+    }
+
+  /* Check if the call to open is the same to the last disk already opened */
+  if (last_devpath && !grub_strcmp(op->open_path,last_devpath))
+  {
+      goto finish;
+  }
+
+ /* If not, we need to close the previous disk and open the new one */
+  else {
+    if (last_ihandle){
+        grub_ieee1275_close (last_ihandle);
+    }
+    last_ihandle = 0;
+    last_devpath = NULL;
+
+    grub_ieee1275_open (op->open_path, &last_ihandle);
+    if (! last_ihandle)
+      return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "can't open device");
+    last_devpath = op->open_path;
+  }
+
   if (grub_ieee1275_finddevice (devpath, &dev))
     {
       grub_free (devpath);
@@ -491,25 +521,18 @@ grub_ofdisk_open (const char *name, grub_disk_t disk)
       return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "not a block device");
     }
 
+
+  finish:
   /* XXX: There is no property to read the number of blocks.  There
      should be a property `#blocks', but it is not there.  Perhaps it
      is possible to use seek for this.  */
   disk->total_sectors = GRUB_DISK_SIZE_UNKNOWN;
 
   {
-    struct ofdisk_hash_ent *op;
-    op = ofdisk_hash_find (devpath);
-    if (!op)
-      op = ofdisk_hash_add (devpath, NULL);
-    if (!op)
-      {
-        grub_free (devpath);
-        return grub_errno;
-      }
     disk->id = (unsigned long) op;
     disk->data = op->open_path;
 
-    err = grub_ofdisk_get_block_size (devpath, &block_size, op);
+    err = grub_ofdisk_get_block_size (&block_size, op);
     if (err)
       {
         grub_free (devpath);
@@ -532,13 +555,6 @@ grub_ofdisk_open (const char *name, grub_disk_t disk)
 static void
 grub_ofdisk_close (grub_disk_t disk)
 {
-  if (disk->data == last_devpath)
-    {
-      if (last_ihandle)
-       grub_ieee1275_close (last_ihandle);
-      last_ihandle = 0;
-      last_devpath = NULL;
-    }
   disk->data = 0;
 }
 
@@ -685,7 +701,7 @@ grub_ofdisk_init (void)
 }
 
 static grub_err_t
-grub_ofdisk_get_block_size (const char *device, grub_uint32_t *block_size,
+grub_ofdisk_get_block_size (grub_uint32_t *block_size,
                            struct ofdisk_hash_ent *op)
 {
   struct size_args_ieee1275
@@ -698,16 +714,6 @@ grub_ofdisk_get_block_size (const char *device, 
grub_uint32_t *block_size,
       grub_ieee1275_cell_t size2;
     } args_ieee1275;
 
-  if (last_ihandle)
-    grub_ieee1275_close (last_ihandle);
-
-  last_ihandle = 0;
-  last_devpath = NULL;
-
-  grub_ieee1275_open (device, &last_ihandle);
-  if (! last_ihandle)
-    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "can't open device");
-
   *block_size = 0;
 
   if (op->block_size_fails >= 2)
-- 
2.21.3