From f8c19ba4661b36d931d7281068a0a66e911acbef Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Tue, 19 Mar 2013 14:49:15 +0000
Subject: [PATCH] A flag for the geom disk driver to indicate that it accepts
 the unmapped i/o requests.

Sponsored by:	The FreeBSD Foundation
Tested by:	pho
---
 sys/geom/geom_disk.c | 20 +++++++++++++++++++-
 sys/geom/geom_disk.h |  1 +
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/sys/geom/geom_disk.c b/sys/geom/geom_disk.c
index 72e9162578a4..7fec9da02387 100644
--- a/sys/geom/geom_disk.c
+++ b/sys/geom/geom_disk.c
@@ -320,13 +320,29 @@ g_disk_start(struct bio *bp)
 		do {
 			bp2->bio_offset += off;
 			bp2->bio_length -= off;
-			bp2->bio_data += off;
+			if ((bp->bio_flags & BIO_UNMAPPED) == 0) {
+				bp2->bio_data += off;
+			} else {
+				KASSERT((dp->d_flags & DISKFLAG_UNMAPPED_BIO)
+				    != 0,
+				    ("unmapped bio not supported by disk %s",
+				    dp->d_name));
+				bp2->bio_ma += off / PAGE_SIZE;
+				bp2->bio_ma_offset += off;
+				bp2->bio_ma_offset %= PAGE_SIZE;
+				bp2->bio_ma_n -= off / PAGE_SIZE;
+			}
 			if (bp2->bio_length > dp->d_maxsize) {
 				/*
 				 * XXX: If we have a stripesize we should really
 				 * use it here.
 				 */
 				bp2->bio_length = dp->d_maxsize;
+				if ((bp->bio_flags & BIO_UNMAPPED) != 0) {
+					bp2->bio_ma_n = howmany(
+					    bp2->bio_ma_offset +
+					    bp2->bio_length, PAGE_SIZE);
+				}
 				off += dp->d_maxsize;
 				/*
 				 * To avoid a race, we need to grab the next bio
@@ -488,6 +504,8 @@ g_disk_create(void *arg, int flag)
 	pp->sectorsize = dp->d_sectorsize;
 	pp->stripeoffset = dp->d_stripeoffset;
 	pp->stripesize = dp->d_stripesize;
+	if ((dp->d_flags & DISKFLAG_UNMAPPED_BIO) != 0)
+		pp->flags |= G_PF_ACCEPT_UNMAPPED;
 	if (bootverbose)
 		printf("GEOM: new disk %s\n", gp->name);
 	sysctl_ctx_init(&sc->sysctl_ctx);
diff --git a/sys/geom/geom_disk.h b/sys/geom/geom_disk.h
index 33d8eb206ab9..246fc497e7b0 100644
--- a/sys/geom/geom_disk.h
+++ b/sys/geom/geom_disk.h
@@ -103,6 +103,7 @@ struct disk {
 #define DISKFLAG_OPEN		0x2
 #define DISKFLAG_CANDELETE	0x4
 #define DISKFLAG_CANFLUSHCACHE	0x8
+#define	DISKFLAG_UNMAPPED_BIO	0x10
 
 struct disk *disk_alloc(void);
 void disk_create(struct disk *disk, int version);