+#define vdev_bdev_block_size(bdev) bdev_logical_block_size(bdev)
+#else
+#define vdev_bdev_block_size(bdev) bdev_hardsect_size(bdev)
+#endif /* HAVE_BDEV_LOGICAL_BLOCK_SIZE */
+#endif /* HAVE_BDEV_PHYSICAL_BLOCK_SIZE */
+
+#ifndef HAVE_BIO_SET_OP_ATTRS
+/*
+ * Kernels without bio_set_op_attrs use bi_rw for the bio flags.
+ */
+static inline void
+bio_set_op_attrs(struct bio *bio, unsigned rw, unsigned flags)
+{
+ bio->bi_rw |= rw | flags;
+}
+#endif
+
+/*
+ * bio_set_flush - Set the appropriate flags in a bio to guarantee
+ * data are on non-volatile media on completion.
+ *
+ * 2.6.X - 2.6.36 API,
+ * WRITE_BARRIER - Tells the block layer to commit all previously submitted
+ * writes to stable storage before this one is started and that the current
+ * write is on stable storage upon completion. Also prevents reordering
+ * on both sides of the current operation.
+ *
+ * 2.6.37 - 4.8 API,
+ * Introduce WRITE_FLUSH, WRITE_FUA, and WRITE_FLUSH_FUA flags as a
+ * replacement for WRITE_BARRIER to allow expressing richer semantics
+ * to the block layer. It's up to the block layer to implement the
+ * semantics correctly. Use the WRITE_FLUSH_FUA flag combination.
+ *
+ * 4.8 - 4.9 API,
+ * REQ_FLUSH was renamed to REQ_PREFLUSH. For consistency with previous
+ * ZoL releases, prefer the WRITE_FLUSH_FUA flag set if it's available.
+ *
+ * 4.10 API,
+ * The read/write flags and their modifiers, including WRITE_FLUSH,
+ * WRITE_FUA and WRITE_FLUSH_FUA were removed from fs.h in
+ * torvalds/linux@70fd7614 and replaced by direct flag modification
+ * of the REQ_ flags in bio->bi_opf. Use REQ_PREFLUSH.
+ */
+static inline void
+bio_set_flush(struct bio *bio)
+{
+#if defined(WRITE_BARRIER) /* < 2.6.37 */
+ bio_set_op_attrs(bio, 0, WRITE_BARRIER);
+#elif defined(WRITE_FLUSH_FUA) /* >= 2.6.37 and <= 4.9 */
+ bio_set_op_attrs(bio, 0, WRITE_FLUSH_FUA);
+#elif defined(REQ_PREFLUSH) /* >= 4.10 */
+ bio_set_op_attrs(bio, 0, REQ_PREFLUSH);