From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Sat, 11 Dec 2010 08:40:32 +0000 (-0800)
Subject: kernel - Make swap, nullfs MPSAFE
X-Git-Url: https://gitweb.dragonflybsd.org/~alexh/dragonfly.git/commitdiff_plain/572a7ed95c499105bcdfceb44aee6f2c118a5bf7

kernel - Make swap, nullfs MPSAFE

* Mark the swap dummy mount as being MPSAFE so strategy operations do not
  acquire the mplock.

* Mark NULLFS mounts as being MPSAFE so operations do not acquire the
  mplock.  If the underlying VFS is not MPSAFE it will still acquire
  the mplock.
---

diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 47fb214fc5..b47cc614e1 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -143,6 +143,7 @@ vfs_mount_init(void)
 	TAILQ_INIT(&mntvnodescan_list);
 	mount_init(&dummymount);
 	dummymount.mnt_flag |= MNT_RDONLY;
+	dummymount.mnt_kern_flag |= MNTK_ALL_MPSAFE;
 }
 
 /*
diff --git a/sys/kern/vfs_vopops.c b/sys/kern/vfs_vopops.c
index 05bb93ce5c..a9944f8422 100644
--- a/sys/kern/vfs_vopops.c
+++ b/sys/kern/vfs_vopops.c
@@ -830,7 +830,6 @@ vop_strategy(struct vop_ops *ops, struct vnode *vp, struct bio *bio)
 	ap.a_bio = bio;
 
 	if (vp->v_mount) {
-
 		VFS_MPLOCK_FLAG(vp->v_mount, MNTK_SG_MPSAFE);
 		DO_OPS(ops, error, &ap, vop_strategy);
 		VFS_MPUNLOCK(vp->v_mount);
diff --git a/sys/vfs/nullfs/null_vfsops.c b/sys/vfs/nullfs/null_vfsops.c
index 57901dfc88..c4b261cd54 100644
--- a/sys/vfs/nullfs/null_vfsops.c
+++ b/sys/vfs/nullfs/null_vfsops.c
@@ -195,9 +195,13 @@ nullfs_mount(struct mount *mp, char *path, caddr_t data, struct ucred *cred)
 		mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntfromname);
 
 	/*
-	 * So unmount won't complain about namecache refs still existing
+	 * Set NCALIASED so unmount won't complain about namecache refs
+	 * still existing.
+	 *
+	 * All NULLFS operations are MPSAFE, though it will be short-lived
+	 * if the underlying filesystem is not.
 	 */
-	mp->mnt_kern_flag |= MNTK_NCALIASED;
+	mp->mnt_kern_flag |= MNTK_NCALIASED | MNTK_ALL_MPSAFE;
 	return (0);
 fail2:
 	nlookup_done(&nd);