From 2b5336a24a542311fa11f5cb39cbdf47a6bbd1ec Mon Sep 17 00:00:00 2001
From: Vladimir 'phcoder' Serbinenko <phcoder@gmail.com>
Date: Sun, 29 Jan 2012 19:00:30 +0100
Subject: [PATCH] 	* include/grub/ata.h (grub_ata): Add a new element
 maxbuffer. 	* grub-core/disk/ata.c (grub_ata_readwrite): Limit to
 ata->maxbuffer. 	* grub-core/disk/pata.c (grub_pata_open): Set
 ata->maxbuffer. 	* grub-core/disk/ahci.c (grub_ahci_open): Likewise.

---
 ChangeLog             | 7 +++++++
 grub-core/disk/ahci.c | 1 +
 grub-core/disk/ata.c  | 7 +++++--
 grub-core/disk/pata.c | 1 +
 include/grub/ata.h    | 2 ++
 5 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index d270c87df..7a0af5e7a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2012-01-29  Vladimir Serbinenko  <phcoder@gmail.com>
+
+	* include/grub/ata.h (grub_ata): Add a new element maxbuffer.
+	* grub-core/disk/ata.c (grub_ata_readwrite): Limit to ata->maxbuffer.
+	* grub-core/disk/pata.c (grub_pata_open): Set ata->maxbuffer.
+	* grub-core/disk/ahci.c (grub_ahci_open): Likewise.
+
 2012-01-29  Vladimir Serbinenko  <phcoder@gmail.com>
 
 	* include/grub/zfs/dnode.h (DN_MIN_INDBLKSHIFT): Removed.
diff --git a/grub-core/disk/ahci.c b/grub-core/disk/ahci.c
index a5a14d414..8c4fc2bfb 100644
--- a/grub-core/disk/ahci.c
+++ b/grub-core/disk/ahci.c
@@ -693,6 +693,7 @@ grub_ahci_open (int id, int devnum, struct grub_ata *ata)
 
   ata->data = dev;
   ata->dma = 1;
+  ata->maxbuffer = GRUB_AHCI_PRDT_MAX_CHUNK_LENGTH;
   ata->present = &dev->present;
 
   return GRUB_ERR_NONE;
diff --git a/grub-core/disk/ata.c b/grub-core/disk/ata.c
index 50559a815..6d2ec0c78 100644
--- a/grub-core/disk/ata.c
+++ b/grub-core/disk/ata.c
@@ -278,6 +278,7 @@ grub_ata_readwrite (grub_disk_t disk, grub_disk_addr_t sector,
   grub_ata_addressing_t addressing = ata->addr;
   grub_size_t batch;
   int cmd, cmd_write;
+  grub_size_t nsectors = 0;
 
   grub_dprintf("ata", "grub_ata_readwrite (size=%llu, rw=%d)\n",
 	       (unsigned long long) size, rw);
@@ -314,9 +315,11 @@ grub_ata_readwrite (grub_disk_t disk, grub_disk_addr_t sector,
 	  cmd = GRUB_ATA_CMD_READ_SECTORS;
 	  cmd_write = GRUB_ATA_CMD_WRITE_SECTORS;
 	}
-    }    
+    }
+
+  if (batch > (ata->maxbuffer >> ata->log_sector_size))
+    batch = (ata->maxbuffer >> ata->log_sector_size);
 
-  grub_size_t nsectors = 0;
   while (nsectors < size)
     {
       struct grub_disk_ata_pass_through_parms parms;
diff --git a/grub-core/disk/pata.c b/grub-core/disk/pata.c
index ff76cc1fb..089059d10 100644
--- a/grub-core/disk/pata.c
+++ b/grub-core/disk/pata.c
@@ -484,6 +484,7 @@ grub_pata_open (int id, int devnum, struct grub_ata *ata)
 
   ata->data = devfnd;
   ata->dma = 0;
+  ata->maxbuffer = 256 * 512;
   ata->present = &devfnd->present;
 
   return GRUB_ERR_NONE;
diff --git a/include/grub/ata.h b/include/grub/ata.h
index 1a19f27aa..efba7b71d 100644
--- a/include/grub/ata.h
+++ b/include/grub/ata.h
@@ -182,6 +182,8 @@ struct grub_ata
 
   int dma;
 
+  grub_size_t maxbuffer;
+
   int *present;
 
   void *data;