Keep track of the mount point associated with a special device

to enable the collection of counts of synchronous and asynchronous
reads and writes for its associated filesystem. The counts are
displayed using `mount -v'.

Ensure that buffers used for paging indicate the vnode from
which they are operating so that counts of paging I/O operations
from the filesystem are collected.

This checkin only adds the setting of the mount point for the
UFS/FFS filesystem, but it would be trivial to add the setting
and clearing of the mount point at filesystem mount/unmount
time for other filesystems too.

Reviewed by: kib

1 files changed, 30 insertions, 1 deletions

diff --git a/sys/geom/geom_vfs.c b/sys/geom/geom_vfs.c
index 9be0000..499445f 100644
--- a/sys/geom/geom_vfs.c
+++ b/sys/geom/geom_vfs.c
@@ -95,6 +95,36 @@ g_vfs_done(struct bio *bip)
 	struct g_vfs_softc *sc;
 	struct buf *bp;
 	int vfslocked, destroy;
+	struct mount *mp;
+	struct vnode *vp;
+
+	/*
+	 * Collect statistics on synchronous and asynchronous read
+	 * and write counts for disks that have associated filesystems.
+	 * Since this run by the g_up thread it is single threaded and
+	 * we do not need to use atomic increments on the counters.
+	 */
+	bp = bip->bio_caller2;
+	vp = bp->b_vp;
+	if (vp == NULL)
+		mp = NULL;
+	else if (vn_isdisk(vp, NULL))
+		mp = vp->v_rdev->si_mountpt;
+	else
+		mp = vp->v_mount;
+	if (mp != NULL) {
+		if (bp->b_iocmd == BIO_WRITE) {
+			if (LK_HOLDER(bp->b_lock.lk_lock) == LK_KERNPROC)
+				mp->mnt_stat.f_asyncwrites++;
+			else
+				mp->mnt_stat.f_syncwrites++;
+		} else {
+			if (LK_HOLDER(bp->b_lock.lk_lock) == LK_KERNPROC)
+				mp->mnt_stat.f_asyncreads++;
+			else
+				mp->mnt_stat.f_syncreads++;
+		}
+	}
 
 	cp = bip->bio_from;
 	sc = cp->geom->softc;
@@ -103,7 +133,6 @@ g_vfs_done(struct bio *bip)
 		g_print_bio(bip);
 		printf("error = %d\n", bip->bio_error);
 	}
-	bp = bip->bio_caller2;
 	bp->b_error = bip->bio_error;
 	bp->b_ioflags = bip->bio_flags;
 	if (bip->bio_error)