Implement a lock in ffs_vget to prevent a race condition where two processes

try allocate the same inode/vnode, causing a duplicate.

Submitted by:	Matt Dillon, slightly reworked by me.

1 files changed, 34 insertions, 4 deletions

diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index f1fdb16..a3595d4 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ffs_vfsops.c	8.8 (Berkeley) 4/18/94
- * $Id: ffs_vfsops.c,v 1.22 1995/06/28 12:01:08 davidg Exp $
+ * $Id: ffs_vfsops.c,v 1.23 1995/07/13 08:48:05 davidg Exp $
  */
 
 #include <sys/param.h>
@@ -737,6 +737,9 @@ loop:
  * return the inode locked.  Detection and handling of mount points must be
  * done by the calling routine.
  */
+
+int	ffs_inode_hash_lock = 0;
+
 int
 ffs_vget(mp, ino, vpp)
 	struct mount *mp;
@@ -756,9 +759,28 @@ ffs_vget(mp, ino, vpp)
 	if ((*vpp = ufs_ihashget(dev, ino)) != NULL)
 		return (0);
 
+	/*
+	 * Lockout the creation of new entries in the FFS hash table
+	 * in case getnewvnode/MALLOC blocks, otherwise a duplicate
+	 * may occur!
+	 */
+	if (ffs_inode_hash_lock) {
+		while (ffs_inode_hash_lock) {
+			ffs_inode_hash_lock = -1;
+			tsleep(&ffs_inode_hash_lock, PVM, "ffsvgt", 0);
+		}
+		if ((*vpp = ufs_ihashget(dev, ino)) != NULL)
+			return (0);
+	}
+	ffs_inode_hash_lock = 1;
+
 	/* Allocate a new vnode/inode. */
 	error = getnewvnode(VT_UFS, mp, ffs_vnodeop_p, &vp);
 	if (error) {
+		if (ffs_inode_hash_lock < 0) {
+			wakeup(&ffs_inode_hash_lock);
+		}
+		ffs_inode_hash_lock = 0;
 		*vpp = NULL;
 		return (error);
 	}
@@ -772,9 +794,9 @@ ffs_vget(mp, ino, vpp)
 	ip->i_number = ino;
 #ifdef QUOTA
 	{
-	int i;
-	for (i = 0; i < MAXQUOTAS; i++)
-		ip->i_dquot[i] = NODQUOT;
+		int i;
+		for (i = 0; i < MAXQUOTAS; i++)
+			ip->i_dquot[i] = NODQUOT;
 	}
 #endif
 	/*
@@ -785,6 +807,14 @@ ffs_vget(mp, ino, vpp)
 	 */
 	ufs_ihashins(ip);
 
+	/*
+	 * Wakeup anybody blocked on our lock
+	 */
+	if (ffs_inode_hash_lock < 0) {
+		wakeup(&ffs_inode_hash_lock);
+	}
+	ffs_inode_hash_lock = 0;
+
 	/* Read in the disk contents for the inode, copy into the inode. */
 	error = bread(ump->um_devvp, fsbtodb(fs, ino_to_fsba(fs, ino)),
 	    (int)fs->fs_bsize, NOCRED, &bp);