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

4 files changed, 42 insertions, 3 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)
diff --git a/sys/sys/conf.h b/sys/sys/conf.h
index 0a12124..49bb3d4 100644
--- a/sys/sys/conf.h
+++ b/sys/sys/conf.h
@@ -52,7 +52,7 @@ struct cdevsw;
 struct file;
 
 struct cdev {
-	void		*__si_reserved;
+	void		*si_spare0;
 	u_int		si_flags;
 #define	SI_ETERNAL	0x0001	/* never destroyed */
 #define	SI_ALIAS	0x0002	/* carrier of alias name */
@@ -78,7 +78,7 @@ struct cdev {
 	LIST_HEAD(, cdev)	si_children;
 	LIST_ENTRY(cdev)	si_siblings;
 	struct cdev *si_parent;
-	void		*si_spare0;
+	struct mount	*si_mountpt;
 	void		*si_drv1, *si_drv2;
 	struct cdevsw	*si_devsw;
 	int		si_iosize_max;	/* maximum I/O size (for physio &al) */
diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index 8871cdf..f38fbcb 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -407,6 +407,8 @@ ffs_mount(struct mount *mp)
 				vn_finished_write(mp);
 				return (error);
 			}
+			if (devvp->v_type == VCHR && devvp->v_rdev != NULL)
+				devvp->v_rdev->si_mountpt = mp;
 			if (fs->fs_snapinum[0] != 0)
 				ffs_snapshot_mount(mp);
 			vn_finished_write(mp);
@@ -1050,6 +1052,8 @@ ffs_mountfs(devvp, mp, td)
 			ffs_flushfiles(mp, FORCECLOSE, td);
 			goto out;
 		}
+		if (devvp->v_type == VCHR && devvp->v_rdev != NULL)
+			devvp->v_rdev->si_mountpt = mp;
 		if (fs->fs_snapinum[0] != 0)
 			ffs_snapshot_mount(mp);
 		fs->fs_fmod = 1;
@@ -1295,6 +1299,8 @@ ffs_unmount(mp, mntflags)
 	g_vfs_close(ump->um_cp);
 	g_topology_unlock();
 	PICKUP_GIANT();
+	if (ump->um_devvp->v_type == VCHR && ump->um_devvp->v_rdev != NULL)
+		ump->um_devvp->v_rdev->si_mountpt = NULL;
 	vrele(ump->um_devvp);
 	dev_rel(ump->um_dev);
 	mtx_destroy(UFS_MTX(ump));
diff --git a/sys/vm/vnode_pager.c b/sys/vm/vnode_pager.c
index c5b6c17..c8c57e1 100644
--- a/sys/vm/vnode_pager.c
+++ b/sys/vm/vnode_pager.c
@@ -543,6 +543,7 @@ vnode_pager_input_smlfs(object, m)
 			bp->b_data = (caddr_t)sf_buf_kva(sf) + i * bsize;
 			bp->b_blkno = fileaddr;
 			pbgetbo(bo, bp);
+			bp->b_vp = vp;
 			bp->b_bcount = bsize;
 			bp->b_bufsize = bsize;
 			bp->b_runningbufspace = bp->b_bufsize;
@@ -560,6 +561,7 @@ vnode_pager_input_smlfs(object, m)
 			/*
 			 * free the buffer header back to the swap buffer pool
 			 */
+			bp->b_vp = NULL;
 			pbrelbo(bp);
 			relpbuf(bp, &vnode_pbuf_freecnt);
 			if (error)
@@ -918,6 +920,7 @@ vnode_pager_generic_getpages(vp, m, bytecount, reqpage)
 	bp->b_wcred = crhold(curthread->td_ucred);
 	bp->b_blkno = firstaddr;
 	pbgetbo(bo, bp);
+	bp->b_vp = vp;
 	bp->b_bcount = size;
 	bp->b_bufsize = size;
 	bp->b_runningbufspace = bp->b_bufsize;
@@ -944,6 +947,7 @@ vnode_pager_generic_getpages(vp, m, bytecount, reqpage)
 	/*
 	 * free the buffer header back to the swap buffer pool
 	 */
+	bp->b_vp = NULL;
 	pbrelbo(bp);
 	relpbuf(bp, &vnode_pbuf_freecnt);