libata: Fix accesses at LBA28 boundary (old bug, but nasty) (v2)

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>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

include/linux/ata.h

@@ -1025,8 +1025,8 @@ static inline int ata_ok(u8 status)
 
 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)