[PATCH] Fix accesses at LBA28 boundary (old bug, but nasty) (v2)

[Mark Lord <kernel@teksavvy.com>]

Most drives from Seagate, Hitachi, and possibly other brands,
do not allow LBA28 access to sector number 0x0fffffff (2^28 - 1).
So instead use LBA48 for such accesses.

This bug could bite a lot of systems, especially when the user has
taken care to align partitions to 4KB boundaries. On misaligned systems,
it is less likely to be encountered, since a 4KB read would end at
0x10000000 rather than at 0x0fffffff.

Signed-off-by: Mark Lord <mlord@pobox.com>
---

Reposting with the pre-existing (u64) cast removed.

--- linux-2.6.34-rc3/include/linux/ata.h	2010-03-30 12:24:39.000000000 -0400
+++ linux/include/linux/ata.h	2010-04-06 18:39:41.167702612 -0400
@@ -1025,8 +1025,8 @@
  
  static inline int lba_28_ok(u64 block, u32 n_block)
  {
-	/* check the ending block number */
-	return ((block + n_block) < ((u64)1 << 28)) && (n_block <= 256);
+	/* check the ending block number: must be LESS THAN 0x0fffffff */
+	return ((block + n_block) < ((1 << 28) - 1)) && (n_block <= 256);
  }
  
  static inline int lba_48_ok(u64 block, u32 n_block)