Major GEOM MULTIPATH class rewrite:

 - Improved locking and destruction process to fix crashes.
 - Improved "automatic" configuration method to make it consistent and safe
by reading metadata back from all specified paths after writing to one.
 - Added provider size check to reduce chance of ordering conflict with
other GEOM classes.
 - Added "manual" configuration method without using on-disk metadata.
 - Added "add" and "remove" commands to allow manage paths manually.
 - Failed paths are no longer dropped from geom, but only marked as FAIL
and excluded from I/O operations.
 - Automatically restore failed paths when all others paths are marked
as failed, for example, because of device-caused (not transport) errors.
 - Added "fail" and "restore" commands to manually control FAIL flag.
 - geom is now destroyed on last path disconnection.
 - Added optional Active/Active mode support. Unlike Active/Passive
mode, load evenly distributed between all working paths. If supported by
the device, it allows to significantly improve performance, utilizing
bandwidth of all paths. It is controlled by -A option during creation.
Disabled by default now.
 - Improved `status` and `list` commands output.

Sponsored by:	iXsystems, inc.
MFC after:	1 month

1 files changed, 12 insertions, 2 deletions

diff --git a/sys/geom/multipath/g_multipath.h b/sys/geom/multipath/g_multipath.h
index 22d6157250ae..33c44f1062ed 100644
--- a/sys/geom/multipath/g_multipath.h
+++ b/sys/geom/multipath/g_multipath.h
@@ -43,10 +43,15 @@
 #ifdef	_KERNEL
 
 struct g_multipath_softc {
-	struct g_provider *	pp;
-	struct g_consumer *	cp_active;
+	struct g_provider *	sc_pp;
+	struct g_consumer *	sc_active;
+	struct mtx		sc_mtx;
 	char			sc_name[16];
 	char			sc_uuid[40];
+	int			sc_opened;
+	int			sc_stopping;
+	int			sc_ndisks;
+	int			sc_active_active; /* Active/Active mode */
 };
 #endif	/* _KERNEL */
 
@@ -57,6 +62,7 @@ struct g_multipath_metadata {
 	uint32_t	md_version;	/* version */
 	uint32_t	md_sectorsize;	/* sectorsize of provider */
 	uint64_t	md_size;	/* absolute size of provider */
+	uint8_t		md_active_active; /* Active/Active mode */
 };
 
 static __inline void
@@ -79,6 +85,8 @@ multipath_metadata_encode(const struct g_multipath_metadata *md, u_char *data)
 	le32enc(data, md->md_sectorsize);
 	data += sizeof(md->md_sectorsize);
 	le64enc(data, md->md_size);
+	data += sizeof(md->md_size);
+	*data = md->md_active_active;
 }
 
 static __inline void
@@ -95,5 +103,7 @@ multipath_metadata_decode(u_char *data, struct g_multipath_metadata *md)
 	md->md_sectorsize = le32dec(data);
 	data += sizeof(md->md_sectorsize);
 	md->md_size = le64dec(data);
+	data += sizeof(md->md_size);
+	md->md_active_active = *data;
 }
 #endif	/* _G_MULTIPATH_H_ */