-#define OST_MAXREQSIZE (16 * 1024)
-#define OST_IO_MAXREQSIZE max_t(int, OST_MAXREQSIZE, \
- (((_OST_MAXREQSIZE_SUM - 1) | (1024 - 1)) + 1))
+#define OST_MAXREQSIZE (16UL * 1024UL)
+#define OST_IO_MAXREQSIZE max(OST_MAXREQSIZE, \
+ ((_OST_MAXREQSIZE_SUM - 1) | \
+ (1024UL - 1)) + 1)
+/* Safe estimate of free space in standard RPC, provides upper limit for # of
+ * bytes of i/o to pack in RPC (skipping bulk transfer). */
+#define OST_SHORT_IO_SPACE (OST_IO_MAXREQSIZE - _OST_MAXREQSIZE_BASE)
+
+/* Actual size used for short i/o buffer. Calculation means this:
+ * At least one page (for large PAGE_SIZE), or 16 KiB, but not more
+ * than the available space aligned to a page boundary. */
+#define OBD_MAX_SHORT_IO_BYTES min(max(PAGE_SIZE, 16UL * 1024UL), \
+ OST_SHORT_IO_SPACE & PAGE_MASK)