[SCSI] tgt: fix the user/kernel ring buffer interface

This patches fixes two bugs in the scsi target infrastructure's
user/kernel interface.

- It wrongly assumes that the ring buffer size of the interface (64KB)
is larger than or equal to the system page size. This patch sets the
ring buffer size to PAGE_SIZE if the system page size is larger.

- It uses PAGE_SIZE in the header file exported to userspace. This
patch removes it.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/scsi_tgt_if.c

@@ -33,6 +33,14 @@
 
 #include "scsi_tgt_priv.h"
 
+#if TGT_RING_SIZE < PAGE_SIZE
+#  define TGT_RING_SIZE PAGE_SIZE
+#endif
+
+#define TGT_RING_PAGES (TGT_RING_SIZE >> PAGE_SHIFT)
+#define TGT_EVENT_PER_PAGE (PAGE_SIZE / sizeof(struct tgt_event))
+#define TGT_MAX_EVENTS (TGT_EVENT_PER_PAGE * TGT_RING_PAGES)
+
 struct tgt_ring {
 	u32 tr_idx;
 	unsigned long tr_pages[TGT_RING_PAGES];

include/scsi/scsi_tgt_if.h

@@ -83,8 +83,5 @@ struct tgt_event {
 } __attribute__ ((aligned (sizeof(uint64_t))));
 
 #define TGT_RING_SIZE (1UL << 16)
-#define TGT_RING_PAGES (TGT_RING_SIZE >> PAGE_SHIFT)
-#define TGT_EVENT_PER_PAGE (PAGE_SIZE / sizeof(struct tgt_event))
-#define TGT_MAX_EVENTS (TGT_EVENT_PER_PAGE * TGT_RING_PAGES)
 
 #endif