From: kettenis <kettenis@openbsd.org>
Date: Wed, 15 Aug 2018 20:22:13 +0000 (+0000)
Subject: Push back the kernel lock in sys_mmap(2) a little bit more now that
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=ef2b82392abad647e6926905905bf5d9235bdab8;p=openbsd

Push back the kernel lock in sys_mmap(2) a little bit more now that
fd_getfile(9) is mpsafe.  Note that sys_mmap(2) isn't actually unlocked
currently.  However this diff has been tested with it unlocked, and I
hope to unlock it for real soon-ish.

ok visa@, mpi@
---

diff --git a/sys/uvm/uvm_mmap.c b/sys/uvm/uvm_mmap.c
index 11effbc411a..e4bf3647f2c 100644
--- a/sys/uvm/uvm_mmap.c
+++ b/sys/uvm/uvm_mmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_mmap.c,v 1.150 2018/04/27 10:13:37 mpi Exp $	*/
+/*	$OpenBSD: uvm_mmap.c,v 1.151 2018/08/15 20:22:13 kettenis Exp $	*/
 /*	$NetBSD: uvm_mmap.c,v 1.49 2001/02/18 21:19:08 chs Exp $	*/
 
 /*
@@ -428,11 +428,8 @@ sys_mmap(struct proc *p, void *v, register_t *retval)
 
 	/* check for file mappings (i.e. not anonymous) and verify file. */
 	if ((flags & MAP_ANON) == 0) {
-		KERNEL_LOCK();
-		if ((fp = fd_getfile(fdp, fd)) == NULL) {
-			KERNEL_UNLOCK();
+		if ((fp = fd_getfile(fdp, fd)) == NULL)
 			return (EBADF);
-		}
 
 		if (fp->f_type != DTYPE_VNODE) {
 			error = ENODEV;		/* only mmap vnodes! */
@@ -456,8 +453,6 @@ sys_mmap(struct proc *p, void *v, register_t *retval)
 			flags |= MAP_ANON;
 			FRELE(fp, p);
 			fp = NULL;
-			/* XXX */
-			KERNEL_UNLOCK();
 			goto is_anon;
 		}
 
@@ -507,8 +502,10 @@ sys_mmap(struct proc *p, void *v, register_t *retval)
 			 * EPERM.
 			 */
 			if (fp->f_flag & FWRITE) {
-				if ((error =
-				    VOP_GETATTR(vp, &va, p->p_ucred, p)))
+				KERNEL_LOCK();
+				error = VOP_GETATTR(vp, &va, p->p_ucred, p);
+				KERNEL_UNLOCK();
+				if (error)
 					goto out;
 				if ((va.va_flags & (IMMUTABLE|APPEND)) == 0)
 					maxprot |= PROT_WRITE;
@@ -533,8 +530,10 @@ sys_mmap(struct proc *p, void *v, register_t *retval)
 				goto out;
 			}
 		}
+		KERNEL_LOCK();
 		error = uvm_mmapfile(&p->p_vmspace->vm_map, &addr, size, prot, maxprot,
 		    flags, vp, pos, p->p_rlimit[RLIMIT_MEMLOCK].rlim_cur, p);
+		KERNEL_UNLOCK();
 	} else {		/* MAP_ANON case */
 		if (fd != -1)
 			return EINVAL;
@@ -568,10 +567,8 @@ is_anon:	/* label for SunOS style /dev/zero */
 		*retval = (register_t)(addr + pageoff);
 
 out:
-	if (fp) {
+	if (fp)
 		FRELE(fp, p);
-		KERNEL_UNLOCK();
-	}
 	return (error);
 }