[PATCH RFC 2/2] vscsiif.h: don't require PAGE_SIZE to be present

[Wei Liu <wei.liu2@citrix.com>]

If it is present, use it; otherwise use 4096. Also provide a new macro
to let user have control over the page size used to do calculation.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Juergen Gross <jgross@suse.com>
---
 xen/include/public/io/vscsiif.h | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/xen/include/public/io/vscsiif.h b/xen/include/public/io/vscsiif.h
index 0a4709f..00e8b74 100644
--- a/xen/include/public/io/vscsiif.h
+++ b/xen/include/public/io/vscsiif.h
@@ -256,7 +256,23 @@ struct scsiif_request_segment {
 };
 typedef struct scsiif_request_segment vscsiif_segment_t;
 
-#define VSCSIIF_SG_PER_PAGE (PAGE_SIZE / sizeof(struct scsiif_request_segment))
+/*
+ * Reference to PAGE_SIZE was overlooked when this header file was
+ * introduced. Respect PAGE_SIZE if defined, otherwise, use 4096.
+ */
+#ifdef PAGE_SIZE
+#define _VSCSIIF_PAGE_SIZE PAGE_SIZE
+#else
+#define _VSCSIIF_PAGE_SIZE 4096
+#endif
+/*
+ * Please use _PAGE2 variant in new code, _PAGE variant is kept for
+ * backward-compatibility.
+ */
+#define VSCSIIF_SG_PER_PAGE (_VSCSI_PAGE_SIZE / \
+                             sizeof(struct scsiif_request_segment))
+#define VSCSIIF_SG_PER_PAGE2(pgsize) ((pgsize) / \
+                                      sizeof(struct scsiif_request_segment))
 
 /* Size of one request is 252 bytes */
 struct vscsiif_request {
-- 
2.1.4


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