Linux 4.8 compat: REQ_OP and bio_set_op_attrs()

New REQ_OP_* definitions have been introduced to separate the
WRITE, READ, and DISCARD operations from the flags.  This included
changing the encoding of bi_rw.  It places REQ_OP_* in high order
bits and other stuff in low order bits.  This encoding is done
through the new helper function bio_set_op_attrs.  For complete
details refer to:

torvalds/linux@f215082
torvalds/linux@4e1b2d5

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#4892
Closes openzfs#4899

include/linux/blkdev_compat.h

@@ -332,15 +332,30 @@ bio_set_flags_failfast(struct block_device *bdev, int *flags)
 #endif
 
 /*
- * 2.6.32 API change
- * Use the normal I/O patch for discards.
+ * 2.6.28 - 2.6.35 API,
+ *   BIO_RW_DISCARD
+ *
+ * 2.6.36 - 4.7 API,
+ *   REQ_DISCARD
+ *
+ * 4.8 - 4.x API,
+ *   REQ_OP_DISCARD
+ *
+ * In all cases the normal I/O path is used for discards.  The only
+ * difference is how the kernel tags individual I/Os as discards.
  */
 #ifdef QUEUE_FLAG_DISCARD
-#ifdef HAVE_BIO_RW_DISCARD
-#define	VDEV_REQ_DISCARD		(1 << BIO_RW_DISCARD)
+static inline boolean_t
+bio_is_discard(struct bio *bio)
+{
+#if defined(HAVE_BIO_RW_DISCARD)
+	return (bio->bi_rw & (1 << BIO_RW_DISCARD));
+#elif defined(REQ_DISCARD)
+	return (bio->bi_rw & REQ_DISCARD);
 #else
-#define	VDEV_REQ_DISCARD		REQ_DISCARD
+	return (bio_op(bio) == REQ_OP_DISCARD);
 #endif
+}
 #else
 #error	"Allowing the build will cause discard requests to become writes "
 	"potentially triggering the DMU_MAX_ACCESS assertion. Please file a "

include/sys/vdev_disk.h

@@ -38,7 +38,7 @@ typedef struct vdev_disk {
 } vdev_disk_t;
 
 extern int vdev_disk_physio(struct block_device *, caddr_t,
-			    size_t, uint64_t, int);
+			    size_t, uint64_t, int, int);
 extern int vdev_disk_read_rootlabel(char *, char *, nvlist_t **);
 
 #endif /* _KERNEL */

module/zfs/vdev_disk.c

@@ -494,41 +494,45 @@ bio_map(struct bio *bio, void *bio_ptr, unsigned int bio_size)
 	return (bio_size);
 }
 
+#ifndef bio_set_op_attrs
+#define	bio_set_op_attrs(bio, rw, flags) \
+	do { (bio)->bi_rw |= (rw)|(flags); } while (0)
+#endif
+
 static inline void
-vdev_submit_bio_impl(int rw, struct bio *bio)
+vdev_submit_bio_impl(struct bio *bio)
 {
 #ifdef HAVE_1ARG_SUBMIT_BIO
-	bio->bi_rw |= rw;
 	submit_bio(bio);
 #else
-	submit_bio(rw, bio);
+	submit_bio(0, bio);
 #endif
 }
 
 static inline void
-vdev_submit_bio(int rw, struct bio *bio)
+vdev_submit_bio(struct bio *bio)
 {
 #ifdef HAVE_CURRENT_BIO_TAIL
 	struct bio **bio_tail = current->bio_tail;
 	current->bio_tail = NULL;
-	vdev_submit_bio_impl(rw, bio);
+	vdev_submit_bio_impl(bio);
 	current->bio_tail = bio_tail;
 #else
 	struct bio_list *bio_list = current->bio_list;
 	current->bio_list = NULL;
-	vdev_submit_bio_impl(rw, bio);
+	vdev_submit_bio_impl(bio);
 	current->bio_list = bio_list;
 #endif
 }
 
 static int
 __vdev_disk_physio(struct block_device *bdev, zio_t *zio, caddr_t kbuf_ptr,
-    size_t kbuf_size, uint64_t kbuf_offset, int flags, int wait)
+    size_t kbuf_size, uint64_t kbuf_offset, int rw, int flags, int wait)
 {
 	dio_request_t *dr;
 	caddr_t bio_ptr;
 	uint64_t bio_offset;
-	int rw, bio_size, bio_count = 16;
+	int bio_size, bio_count = 16;
 	int i = 0, error = 0;
 
 	ASSERT3U(kbuf_offset + kbuf_size, <=, bdev->bd_inode->i_size);
@@ -541,7 +545,6 @@ __vdev_disk_physio(struct block_device *bdev, zio_t *zio, caddr_t kbuf_ptr,
 	if (zio && !(zio->io_flags & (ZIO_FLAG_IO_RETRY | ZIO_FLAG_TRYHARD)))
 		bio_set_flags_failfast(bdev, &flags);
 
-	rw = flags;
 	dr->dr_zio = zio;
 	dr->dr_wait = wait;
 
@@ -585,9 +588,9 @@ __vdev_disk_physio(struct block_device *bdev, zio_t *zio, caddr_t kbuf_ptr,
 
 		dr->dr_bio[i]->bi_bdev = bdev;
 		BIO_BI_SECTOR(dr->dr_bio[i]) = bio_offset >> 9;
-		dr->dr_bio[i]->bi_rw = rw;
 		dr->dr_bio[i]->bi_end_io = vdev_disk_physio_completion;
 		dr->dr_bio[i]->bi_private = dr;
+		bio_set_op_attrs(dr->dr_bio[i], rw, flags);
 
 		/* Remaining size is returned to become the new size */
 		bio_size = bio_map(dr->dr_bio[i], bio_ptr, bio_size);
@@ -605,7 +608,7 @@ __vdev_disk_physio(struct block_device *bdev, zio_t *zio, caddr_t kbuf_ptr,
 	/* Submit all bio's associated with this dio */
 	for (i = 0; i < dr->dr_bio_count; i++)
 		if (dr->dr_bio[i])
-			vdev_submit_bio(rw, dr->dr_bio[i]);
+			vdev_submit_bio(dr->dr_bio[i]);
 
 	/*
 	 * On synchronous blocking requests we wait for all bio the completion
@@ -628,10 +631,11 @@ __vdev_disk_physio(struct block_device *bdev, zio_t *zio, caddr_t kbuf_ptr,
 
 int
 vdev_disk_physio(struct block_device *bdev, caddr_t kbuf,
-    size_t size, uint64_t offset, int flags)
+    size_t size, uint64_t offset, int rw, int flags)
 {
 	bio_set_flags_failfast(bdev, &flags);
-	return (__vdev_disk_physio(bdev, NULL, kbuf, size, offset, flags, 1));
+	return (__vdev_disk_physio(bdev, NULL, kbuf, size, offset, rw, flags,
+	    1));
 }
 
 BIO_END_IO_PROTO(vdev_disk_io_flush_completion, bio, rc)
@@ -672,7 +676,8 @@ vdev_disk_io_flush(struct block_device *bdev, zio_t *zio)
 	bio->bi_private = zio;
 	bio->bi_bdev = bdev;
 	zio->io_delay = jiffies_64;
-	vdev_submit_bio(VDEV_WRITE_FLUSH_FUA, bio);
+	bio_set_op_attrs(bio, 0, VDEV_WRITE_FLUSH_FUA);
+	vdev_submit_bio(bio);
 	invalidate_bdev(bdev);
 
 	return (0);
@@ -684,7 +689,7 @@ vdev_disk_io_start(zio_t *zio)
 	vdev_t *v = zio->io_vd;
 	vdev_disk_t *vd = v->vdev_tsd;
 	zio_priority_t pri = zio->io_priority;
-	int flags, error;
+	int rw, flags, error;
 
 	switch (zio->io_type) {
 	case ZIO_TYPE_IOCTL:
@@ -723,17 +728,19 @@ vdev_disk_io_start(zio_t *zio)
 		zio_execute(zio);
 		return;
 	case ZIO_TYPE_WRITE:
+		rw = WRITE;
 		if ((pri == ZIO_PRIORITY_SYNC_WRITE) && (v->vdev_nonrot))
 			flags = WRITE_SYNC;
 		else
-			flags = WRITE;
+			flags = 0;
 		break;
 
 	case ZIO_TYPE_READ:
+		rw = READ;
 		if ((pri == ZIO_PRIORITY_SYNC_READ) && (v->vdev_nonrot))
 			flags = READ_SYNC;
 		else
-			flags = READ;
+			flags = 0;
 		break;
 
 	default:
@@ -743,7 +750,7 @@ vdev_disk_io_start(zio_t *zio)
 	}
 
 	error = __vdev_disk_physio(vd->vd_bdev, zio, zio->io_data,
-	    zio->io_size, zio->io_offset, flags, 0);
+	    zio->io_size, zio->io_offset, rw, flags, 0);
 	if (error) {
 		zio->io_error = error;
 		zio_interrupt(zio);
@@ -844,7 +851,8 @@ vdev_disk_read_rootlabel(char *devpath, char *devid, nvlist_t **config)
 		/* read vdev label */
 		offset = vdev_label_offset(size, i, 0);
 		if (vdev_disk_physio(bdev, (caddr_t)label,
-		    VDEV_SKIP_SIZE + VDEV_PHYS_SIZE, offset, READ_SYNC) != 0)
+		    VDEV_SKIP_SIZE + VDEV_PHYS_SIZE, offset, READ,
+		    REQ_SYNC) != 0)
 			continue;
 
 		if (nvlist_unpack(label->vl_vdev_phys.vp_nvlist,

module/zfs/zvol.c

@@ -766,7 +766,7 @@ zvol_request(struct request_queue *q, struct bio *bio)
 			goto out2;
 		}
 
-		if (bio->bi_rw & VDEV_REQ_DISCARD) {
+		if (bio_is_discard(bio)) {
 			error = zvol_discard(bio);
 			goto out2;
 		}