Rewamp DEVFS internals pretty severely [1].

Give DEVFS a proper inode called struct cdev_priv.  It is important
to keep in mind that this "inode" is shared between all DEVFS
mountpoints, therefore it is protected by the global device mutex.

Link the cdev_priv's into a list, protected by the global device
mutex.  Keep track of each cdev_priv's state with a flag bit and
of references from mountpoints with a dedicated usecount.

Reap the benefits of much improved kernel memory allocator and the
generally better defined device driver APIs to get rid of the tables
of pointers + serial numbers, their overflow tables,  the atomics
to muck about in them and all the trouble that resulted in.

This makes RAM the only limit on how many devices we can have.

The cdev_priv is actually a super struct containing the normal cdev
as the "public" part, and therefore allocation and freeing has moved
to devfs_devs.c from kern_conf.c.

The overall responsibility is (to be) split such that kern/kern_conf.c
is the stuff that deals with drivers and struct cdev and fs/devfs
handles filesystems and struct cdev_priv and their private liason
exposed only in devfs_int.h.

Move the inode number from cdev to cdev_priv and allocate inode
numbers properly with unr.  Local dirents in the mountpoints
(directories, symlinks) allocate inodes from the same pool to
guarantee against overlaps.

Various other fields are going to migrate from cdev to cdev_priv
in the future in order to hide them.  A few fields may migrate
from devfs_dirent to cdev_priv as well.

Protect the DEVFS mountpoint with an sx lock instead of lockmgr,
this lock also protects the directory tree of the mountpoint.

Give each mountpoint a unique integer index, allocated with unr.
Use it into an array of devfs_dirent pointers in each cdev_priv.
Initially the array points to a single element also inside cdev_priv,
but as more devfs instances are mounted, the array is extended with
malloc(9) as necessary when the filesystem populates its directory
tree.

Retire the cdev alias lists, the cdev_priv now know about all the
relevant devfs_dirents (and their vnodes) and devfs_revoke() will
pick them up from there.  We still spelunk into other mountpoints
and fondle their data without 100% good locking.  It may make better
sense to vector the revoke event into the tty code and there do a
destroy_dev/make_dev on the tty's devices, but that's for further
study.

Lots of shuffling of stuff and churn of bits for no good reason[2].

XXX: There is still nothing preventing the dev_clone EVENTHANDLER
from being invoked at the same time in two devfs mountpoints.  It
is not obvious what the best course of action is here.

XXX: comment out an if statement that lost its body, until I can
find out what should go there so it doesn't do damage in the meantime.

XXX: Leave in a few extra malloc types and KASSERTS to help track
down any remaining issues.

Much testing provided by:		Kris
Much confusion caused by (races in):	md(4)

[1] You are not supposed to understand anything past this point.

[2] This line should simplify life for the peanut gallery.

1 files changed, 79 insertions, 113 deletions

diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c
index 6cf2f49..f14f480 100644
--- a/sys/fs/devfs/devfs_vnops.c
+++ b/sys/fs/devfs/devfs_vnops.c
@@ -37,7 +37,6 @@
 /*
  * TODO:
  *	remove empty directories
- *	mknod: hunt down DE_DELETED, compare name, reinstantiate.
  *	mkdir: want it ?
  */
 
@@ -71,6 +70,8 @@ static struct vop_vector devfs_specops;
 static struct fileops devfs_ops_f;
 
 #include <fs/devfs/devfs.h>
+#include <fs/devfs/devfs_int.h>
+
 static int
 devfs_fp_check(struct file *fp, struct cdev **devp, struct cdevsw **dswp)
 {
@@ -139,9 +140,9 @@ loop:
 		return (0);
 	}
 	if (de->de_dirent->d_type == DT_CHR) {
-		dev = *devfs_itod(de->de_inode);
-		if (dev == NULL)
+		if (!(de->de_cdp->cdp_flags & CDP_ACTIVE))
 			return (ENOENT);
+		dev = &de->de_cdp->cdp_c;
 	} else {
 		dev = NULL;
 	}
@@ -157,7 +158,8 @@ loop:
 		dev_lock();
 		dev_refl(dev);
 		vp->v_rdev = dev;
-		LIST_INSERT_HEAD(&dev->si_alist, de, de_alias);
+		KASSERT(vp->v_usecount == 1,
+		    ("%s %d (%d)\n", __func__, __LINE__, vp->v_usecount));
 		dev->si_usecount += vp->v_usecount;
 		dev_unlock();
 		VI_UNLOCK(vp);
@@ -204,9 +206,6 @@ devfs_access(struct vop_access_args *ap)
 	return (error);
 }
 
-/*
- * Special device advisory byte-level locks.
- */
 /* ARGSUSED */
 static int
 devfs_advlock(struct vop_advlock_args *ap)
@@ -215,9 +214,6 @@ devfs_advlock(struct vop_advlock_args *ap)
 	return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
 }
 
-/*
- * Device close routine
- */
 /* ARGSUSED */
 static int
 devfs_close(struct vop_close_args *ap)
@@ -301,9 +297,6 @@ devfs_close_f(struct file *fp, struct thread *td)
 	return (vnops.fo_close(fp, td));
 }
 
-/*
- * Synch buffers associated with a block device
- */
 /* ARGSUSED */
 static int
 devfs_fsync(struct vop_fsync_args *ap)
@@ -370,7 +363,7 @@ devfs_getattr(struct vop_getattr_args *ap)
 		fix(dev->si_ctime);
 		vap->va_ctime = dev->si_ctime;
 
-		vap->va_rdev = dev->si_inode;
+		vap->va_rdev = dev->si_priv->cdp_inode;
 	}
 	vap->va_gen = 0;
 	vap->va_flags = 0;
@@ -380,9 +373,6 @@ devfs_getattr(struct vop_getattr_args *ap)
 	return (error);
 }
 
-/*
- * Device ioctl operation.
- */
 /* ARGSUSED */
 static int
 devfs_ioctl_f(struct file *fp, u_long com, void *data, struct ucred *cred, struct thread *td)
@@ -446,7 +436,6 @@ devfs_ioctl_f(struct file *fp, u_long com, void *data, struct ucred *cred, struc
 	return (error);
 }
 
-
 /* ARGSUSED */
 static int
 devfs_kqfilter_f(struct file *fp, struct knote *kn)
@@ -520,65 +509,47 @@ devfs_lookupx(struct vop_lookup_args *ap)
 		return (error);
 	}
 
-	lockmgr(&dmp->dm_lock, LK_UPGRADE, 0, curthread);
 	devfs_populate(dmp);
-	lockmgr(&dmp->dm_lock, LK_DOWNGRADE, 0, curthread);
 	dd = dvp->v_data;
-	TAILQ_FOREACH(de, &dd->de_dlist, de_list) {
-		if (cnp->cn_namelen != de->de_dirent->d_namlen)
-			continue;
-		if (bcmp(cnp->cn_nameptr, de->de_dirent->d_name,
-		    de->de_dirent->d_namlen) != 0)
-			continue;
-		if (de->de_flags & DE_WHITEOUT)
-			goto notfound;
-		goto found;
-	}
-
-	if (nameiop == DELETE)
-		goto notfound;
-
-	/*
-	 * OK, we didn't have an entry for the name we were asked for
-	 * so we try to see if anybody can create it on demand.
-	 */
-	pname = devfs_fqpn(specname, dvp, cnp);
-	if (pname == NULL)
-		goto notfound;
+	de = devfs_find(dd, cnp->cn_nameptr, cnp->cn_namelen);
+	while (de == NULL) {	/* While(...) so we can use break */
 
-	cdev = NULL;
-	EVENTHANDLER_INVOKE(dev_clone, td->td_ucred, pname, strlen(pname),
-	    &cdev);
-	if (cdev == NULL)
-		goto notfound;
-
-	lockmgr(&dmp->dm_lock, LK_UPGRADE, 0, curthread);
-	devfs_populate(dmp);
-	lockmgr(&dmp->dm_lock, LK_DOWNGRADE, 0, curthread);
-
-	dde = devfs_itode(dmp, cdev->si_inode);
-	dev_rel(cdev);
-
-	if (dde == NULL || *dde == NULL || *dde == DE_DELETED)
-		goto notfound;
+		if (nameiop == DELETE)
+			return (ENOENT);
 
-	if ((*dde)->de_flags & DE_WHITEOUT)
-		goto notfound;
+		/*
+		 * OK, we didn't have an entry for the name we were asked for
+		 * so we try to see if anybody can create it on demand.
+		 */
+		pname = devfs_fqpn(specname, dvp, cnp);
+		if (pname == NULL)
+			break;
 
-	de = *dde;
-	goto found;
+		cdev = NULL;
+		EVENTHANDLER_INVOKE(dev_clone,
+		    td->td_ucred, pname, strlen(pname), &cdev);
+		if (cdev == NULL)
+			break;
 
-notfound:
+		devfs_populate(dmp);
 
-	if ((nameiop == CREATE || nameiop == RENAME) &&
-	    (flags & (LOCKPARENT | WANTPARENT)) && (flags & ISLASTCN)) {
-		cnp->cn_flags |= SAVENAME;
-		return (EJUSTRETURN);
+		dev_lock();
+		dde = &cdev->si_priv->cdp_dirents[dmp->dm_idx];
+		if (dde != NULL && *dde != NULL)
+			de = *dde;
+		dev_unlock();
+		dev_rel(cdev);
+		break;
 	}
-	return (ENOENT);
-
 
-found:
+	if (de == NULL || de->de_flags & DE_WHITEOUT) {
+		if ((nameiop == CREATE || nameiop == RENAME) &&
+		    (flags & (LOCKPARENT | WANTPARENT)) && (flags & ISLASTCN)) {
+			cnp->cn_flags |= SAVENAME;
+			return (EJUSTRETURN);
+		}
+		return (ENOENT);
+	}
 
 	if ((cnp->cn_nameiop == DELETE) && (flags & ISLASTCN)) {
 		error = VOP_ACCESS(dvp, VWRITE, cnp->cn_cred, td);
@@ -589,10 +560,6 @@ found:
 			*vpp = dvp;
 			return (0);
 		}
-		error = devfs_allocv(de, dvp->v_mount, vpp, td);
-		if (error)
-			return (error);
-		return (0);
 	}
 	error = devfs_allocv(de, dvp->v_mount, vpp, td);
 	return (error);
@@ -605,9 +572,9 @@ devfs_lookup(struct vop_lookup_args *ap)
 	struct devfs_mount *dmp;
 
 	dmp = VFSTODEVFS(ap->a_dvp->v_mount);
-	lockmgr(&dmp->dm_lock, LK_SHARED, 0, curthread);
+	sx_xlock(&dmp->dm_lock);
 	j = devfs_lookupx(ap);
-	lockmgr(&dmp->dm_lock, LK_RELEASE, 0, curthread);
+	sx_xunlock(&dmp->dm_lock);
 	return (j);
 }
 
@@ -629,7 +596,7 @@ devfs_mknod(struct vop_mknod_args *ap)
 		return (EOPNOTSUPP);
 	dvp = ap->a_dvp;
 	dmp = VFSTODEVFS(dvp->v_mount);
-	lockmgr(&dmp->dm_lock, LK_EXCLUSIVE, 0, curthread);
+	sx_xlock(&dmp->dm_lock);
 
 	cnp = ap->a_cnp;
 	vpp = ap->a_vpp;
@@ -652,13 +619,10 @@ devfs_mknod(struct vop_mknod_args *ap)
 	de->de_flags &= ~DE_WHITEOUT;
 	error = devfs_allocv(de, dvp->v_mount, vpp, td);
 notfound:
-	lockmgr(&dmp->dm_lock, LK_RELEASE, 0, curthread);
+	sx_xunlock(&dmp->dm_lock);
 	return (error);
 }
 
-/*
- * Open a special file.
- */
 /* ARGSUSED */
 static int
 devfs_open(struct vop_open_args *ap)
@@ -793,9 +757,6 @@ devfs_print(struct vop_print_args *ap)
 	return (0);
 }
 
-/*
- * Vnode op for read
- */
 /* ARGSUSED */
 static int
 devfs_read_f(struct file *fp, struct uio *uio, struct ucred *cred, int flags, struct thread *td)
@@ -845,18 +806,14 @@ devfs_readdir(struct vop_readdir_args *ap)
 		return (EINVAL);
 
 	dmp = VFSTODEVFS(ap->a_vp->v_mount);
-	lockmgr(&dmp->dm_lock, LK_EXCLUSIVE, 0, curthread);
+	sx_xlock(&dmp->dm_lock);
 	devfs_populate(dmp);
-	lockmgr(&dmp->dm_lock, LK_DOWNGRADE, 0, curthread);
 	error = 0;
 	de = ap->a_vp->v_data;
 	off = 0;
 	oldoff = uio->uio_offset;
-	if (ap->a_ncookies != NULL) {
-		*ap->a_ncookies = 0;
-		*ap->a_cookies = NULL;
-	}
 	TAILQ_FOREACH(dd, &de->de_dlist, de_list) {
+		KASSERT(dd->de_cdp != (void *)0xdeadc0de, ("%s %d\n", __func__, __LINE__));
 		if (dd->de_flags & DE_WHITEOUT)
 			continue;
 		if (dd->de_dirent->d_type == DT_DIR)
@@ -874,7 +831,7 @@ devfs_readdir(struct vop_readdir_args *ap)
 		}
 		off += dp->d_reclen;
 	}
-	lockmgr(&dmp->dm_lock, LK_RELEASE, 0, curthread);
+	sx_xunlock(&dmp->dm_lock);
 	uio->uio_offset = off;
 	return (error);
 }
@@ -908,8 +865,6 @@ devfs_reclaim(struct vop_reclaim_args *ap)
 		return (0);
 
 	dev_lock();
-	if (de != NULL)
-		LIST_REMOVE(de, de_alias);
 	dev->si_usecount -= vp->v_usecount;
 	dev_unlock();
 	dev_rel(dev);
@@ -924,21 +879,16 @@ devfs_remove(struct vop_remove_args *ap)
 	struct devfs_dirent *de;
 	struct devfs_mount *dmp = VFSTODEVFS(vp->v_mount);
 
-	lockmgr(&dmp->dm_lock, LK_EXCLUSIVE, 0, curthread);
+	sx_xlock(&dmp->dm_lock);
 	dd = ap->a_dvp->v_data;
 	de = vp->v_data;
 	if (de->de_dirent->d_type == DT_LNK) {
 		TAILQ_REMOVE(&dd->de_dlist, de, de_list);
-		if (de->de_vnode)
-			de->de_vnode->v_data = NULL;
-#ifdef MAC
-		mac_destroy_devfsdirent(de);
-#endif
-		free(de, M_DEVFS);
+		devfs_delete(dmp, de);
 	} else {
 		de->de_flags |= DE_WHITEOUT;
 	}
-	lockmgr(&dmp->dm_lock, LK_RELEASE, 0, curthread);
+	sx_xunlock(&dmp->dm_lock);
 	return (0);
 }
 
@@ -946,24 +896,43 @@ devfs_remove(struct vop_remove_args *ap)
  * Revoke is called on a tty when a terminal session ends.  The vnode
  * is orphaned by setting v_op to deadfs so we need to let go of it
  * as well so that we create a new one next time around.
+ *
+ * XXX: locking :-(
+ * XXX: We mess around with other mountpoints without holding their sxlock.
+ * XXX: We hold the devlock() when we zero their vnode pointer, but is that
+ * XXX: enough ?
  */
 static int
 devfs_revoke(struct vop_revoke_args *ap)
 {
-	struct vnode *vp = ap->a_vp;
+	struct vnode *vp = ap->a_vp, *vp2;
 	struct cdev *dev;
+	struct cdev_priv *cdp;
 	struct devfs_dirent *de;
+	int i;
 
 	KASSERT((ap->a_flags & REVOKEALL) != 0, ("devfs_revoke !REVOKEALL"));
 
 	dev = vp->v_rdev;
+	cdp = dev->si_priv;
 	for (;;) {
 		dev_lock();
-		de = LIST_FIRST(&dev->si_alist);
+		vp2 = NULL;
+		for (i = 0; i <= cdp->cdp_maxdirent; i++) {
+			de = cdp->cdp_dirents[i];
+			if (de == NULL)
+				continue;
+			vp2 = de->de_vnode;
+			de->de_vnode = NULL;
+			if (vp2 != NULL)
+				break;
+		}
 		dev_unlock();
-		if (de == NULL)
-			break;
-		vgone(de->de_vnode);
+		if (vp2 != NULL) {
+			vgone(vp2);
+			continue;
+		}
+		break;
 	}
 	return (0);
 }
@@ -975,10 +944,10 @@ devfs_rioctl(struct vop_ioctl_args *ap)
 	struct devfs_mount *dmp;
 
 	dmp = VFSTODEVFS(ap->a_vp->v_mount);
-	lockmgr(&dmp->dm_lock, LK_EXCLUSIVE, 0, curthread);
+	sx_xlock(&dmp->dm_lock);
 	devfs_populate(dmp);
 	error = devfs_rules_ioctl(dmp, ap->a_command, ap->a_data, ap->a_td);
-	lockmgr(&dmp->dm_lock, LK_RELEASE, 0, curthread);
+	sx_xunlock(&dmp->dm_lock);
 	return (error);
 }
 
@@ -1120,24 +1089,21 @@ devfs_symlink(struct vop_symlink_args *ap)
 	de->de_uid = 0;
 	de->de_gid = 0;
 	de->de_mode = 0755;
-	de->de_inode = dmp->dm_inode++;
+	de->de_inode = alloc_unr(devfs_inos);
 	de->de_dirent->d_type = DT_LNK;
 	i = strlen(ap->a_target) + 1;
 	de->de_symlink = malloc(i, M_DEVFS, M_WAITOK);
 	bcopy(ap->a_target, de->de_symlink, i);
-	lockmgr(&dmp->dm_lock, LK_EXCLUSIVE, 0, td);
+	sx_xlock(&dmp->dm_lock);
 #ifdef MAC
 	mac_create_devfs_symlink(ap->a_cnp->cn_cred, dmp->dm_mount, dd, de);
 #endif
 	TAILQ_INSERT_TAIL(&dd->de_dlist, de, de_list);
 	devfs_allocv(de, ap->a_dvp->v_mount, ap->a_vpp, td);
-	lockmgr(&dmp->dm_lock, LK_RELEASE, 0, td);
+	sx_xunlock(&dmp->dm_lock);
 	return (0);
 }
 
-/*
- * Vnode op for write
- */
 /* ARGSUSED */
 static int
 devfs_write_f(struct file *fp, struct uio *uio, struct ucred *cred, int flags, struct thread *td)
@@ -1176,7 +1142,7 @@ dev2udev(struct cdev *x)
 {
 	if (x == NULL)
 		return (NODEV);
-	return (x->si_inode);
+	return (x->si_priv->cdp_inode);
 }
 
 static struct fileops devfs_ops_f = {