From 21fc02d2711ef2c49b615eee2362a33a78f9d39a Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Mon, 3 Nov 2008 20:31:00 +0000
Subject: [PATCH] Use shared vnode locks instead of exclusive vnode locks for
 the access(), chdir(), chroot(), eaccess(), fpathconf(), fstat(), fstatfs(),
 lseek() (when figuring out the current size of the file in the SEEK_END
 case), pathconf(), readlink(), and statfs() system calls.

Submitted by:	ups (mostly)
Tested by:	pho
MFC after:	1 month
---
 sys/kern/kern_descrip.c |  2 +-
 sys/kern/vfs_syscalls.c | 28 ++++++++++++++--------------
 sys/kern/vfs_vnops.c    |  2 +-
 3 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index ec07d0f6ed9a..df92aca1fdf8 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -1241,7 +1241,7 @@ fpathconf(struct thread *td, struct fpathconf_args *uap)
 	if (vp != NULL) {
 		int vfslocked;
 		vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+		vn_lock(vp, LK_SHARED | LK_RETRY);
 		error = VOP_PATHCONF(vp, uap->name, td->td_retval);
 		VOP_UNLOCK(vp, 0);
 		VFS_UNLOCK_GIANT(vfslocked);
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 32dc4d134bc0..4bdfc09bc317 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -286,8 +286,8 @@ kern_statfs(struct thread *td, char *path, enum uio_seg pathseg,
 	int error;
 	struct nameidata nd;
 
-	NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | MPSAFE | AUDITVNODE1,
-	    pathseg, path, td);
+	NDINIT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | MPSAFE |
+	    AUDITVNODE1, pathseg, path, td);
 	error = namei(&nd);
 	if (error)
 		return (error);
@@ -368,7 +368,7 @@ kern_fstatfs(struct thread *td, int fd, struct statfs *buf)
 		return (error);
 	vp = fp->f_vnode;
 	vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+	vn_lock(vp, LK_SHARED | LK_RETRY);
 #ifdef AUDIT
 	AUDIT_ARG(vnode, vp, ARG_VNODE1);
 #endif
@@ -800,8 +800,8 @@ kern_chdir(struct thread *td, char *path, enum uio_seg pathseg)
 	struct vnode *vp;
 	int vfslocked;
 
-	NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1 | MPSAFE,
-	    pathseg, path, td);
+	NDINIT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | AUDITVNODE1 |
+	    MPSAFE, pathseg, path, td);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	vfslocked = NDHASGIANT(&nd);
@@ -886,8 +886,8 @@ chroot(td, uap)
 	error = priv_check(td, PRIV_VFS_CHROOT);
 	if (error)
 		return (error);
-	NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | MPSAFE | AUDITVNODE1,
-	    UIO_USERSPACE, uap->path, td);
+	NDINIT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | MPSAFE |
+	    AUDITVNODE1, UIO_USERSPACE, uap->path, td);
 	error = namei(&nd);
 	if (error)
 		goto error;
@@ -1938,7 +1938,7 @@ lseek(td, uap)
 		offset += fp->f_offset;
 		break;
 	case L_XTND:
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+		vn_lock(vp, LK_SHARED | LK_RETRY);
 		error = VOP_GETATTR(vp, &vattr, cred);
 		VOP_UNLOCK(vp, 0);
 		if (error)
@@ -2125,8 +2125,8 @@ kern_accessat(struct thread *td, int fd, char *path, enum uio_seg pathseg,
 		td->td_ucred = tmpcred;
 	} else
 		cred = tmpcred = td->td_ucred;
-	NDINIT_AT(&nd, LOOKUP, FOLLOW | LOCKLEAF | MPSAFE | AUDITVNODE1,
-	    pathseg, path, fd, td);
+	NDINIT_AT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | MPSAFE |
+	    AUDITVNODE1, pathseg, path, fd, td);
 	if ((error = namei(&nd)) != 0)
 		goto out1;
 	vfslocked = NDHASGIANT(&nd);
@@ -2492,8 +2492,8 @@ kern_pathconf(struct thread *td, char *path, enum uio_seg pathseg, int name)
 	struct nameidata nd;
 	int error, vfslocked;
 
-	NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | MPSAFE | AUDITVNODE1,
-	    pathseg, path, td);
+	NDINIT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | MPSAFE |
+	    AUDITVNODE1, pathseg, path, td);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	vfslocked = NDHASGIANT(&nd);
@@ -2568,8 +2568,8 @@ kern_readlinkat(struct thread *td, int fd, char *path, enum uio_seg pathseg,
 	struct nameidata nd;
 	int vfslocked;
 
-	NDINIT_AT(&nd, LOOKUP, NOFOLLOW | LOCKLEAF | MPSAFE | AUDITVNODE1,
-	    pathseg, path, fd, td);
+	NDINIT_AT(&nd, LOOKUP, NOFOLLOW | LOCKSHARED | LOCKLEAF | MPSAFE |
+	    AUDITVNODE1, pathseg, path, fd, td);
 
 	if ((error = namei(&nd)) != 0)
 		return (error);
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index b272a9406406..f631508b5b52 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -673,7 +673,7 @@ vn_statfile(fp, sb, active_cred, td)
 	int error;
 
 	vfslocked = VFS_LOCK_GIANT(vp->v_mount);
-	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+	vn_lock(vp, LK_SHARED | LK_RETRY);
 	error = vn_stat(vp, sb, active_cred, fp->f_cred, td);
 	VOP_UNLOCK(vp, 0);
 	VFS_UNLOCK_GIANT(vfslocked);