svn commit: r305593 - head/sys/ufs/ufs

[Konstantin Belousov]

Author: kib
Date: Thu Sep  8 12:04:45 2016
New Revision: 305593
URL: https://svnweb.freebsd.org/changeset/base/305593

Log:
  There is no need to upgrade the last dvp lock on lookups for modifying
  operations.  Instead of upgrading, assert that the lock is exclusive.
  Explain the cause in comments.
  
  This effectively reverts r209367.
  
  Tested by:	pho
  Reviewed by:	mckusick
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks

Modified:
  head/sys/ufs/ufs/ufs_lookup.c

Modified: head/sys/ufs/ufs/ufs_lookup.c
==============================================================================
--- head/sys/ufs/ufs/ufs_lookup.c	Thu Sep  8 12:01:28 2016	(r305592)
+++ head/sys/ufs/ufs/ufs_lookup.c	Thu Sep  8 12:04:45 2016	(r305593)
@@ -76,32 +76,6 @@ SYSCTL_INT(_debug, OID_AUTO, dircheck, C
 /* true if old FS format...*/
 #define OFSFMT(vp)	((vp)->v_mount->mnt_maxsymlinklen <= 0)
 
-#ifdef QUOTA
-static int
-ufs_lookup_upgrade_lock(struct vnode *vp)
-{
-	int error;
-
-	ASSERT_VOP_LOCKED(vp, __FUNCTION__);
-	if (VOP_ISLOCKED(vp) == LK_EXCLUSIVE)
-		return (0);
-
-	error = 0;
-
-	/*
-	 * Upgrade vnode lock, since getinoquota()
-	 * requires exclusive lock to modify inode.
-	 */
-	vhold(vp);
-	vn_lock(vp, LK_UPGRADE | LK_RETRY);
-	VI_LOCK(vp);
-	if (vp->v_iflag & VI_DOOMED)
-		error = ENOENT;
-	vdropl(vp);
-	return (error);
-}
-#endif
-
 static int
 ufs_delete_denied(struct vnode *vdp, struct vnode *tdp, struct ucred *cred,
     struct thread *td)
@@ -259,12 +233,25 @@ ufs_lookup_ino(struct vnode *vdp, struct
 	vnode_create_vobject(vdp, DIP(dp, i_size), cnp->cn_thread);
 
 	bmask = VFSTOUFS(vdp->v_mount)->um_mountp->mnt_stat.f_iosize - 1;
-#ifdef QUOTA
-	if ((nameiop == DELETE || nameiop == RENAME) && (flags & ISLASTCN)) {
-		error = ufs_lookup_upgrade_lock(vdp);
-		if (error != 0)
-			return (error);
-	}
+
+#ifdef DEBUG_VFS_LOCKS
+	/*
+	 * Assert that the directory vnode is locked, and locked
+	 * exclusively for the last component lookup for modifying
+	 * operations.
+	 *
+	 * The directory-modifying operations need to save
+	 * intermediate state in the inode between namei() call and
+	 * actual directory manipulations.  See fields in the struct
+	 * inode marked as 'used during directory lookup'.  We must
+	 * ensure that upgrade in namei() does not happen, since
+	 * upgrade might need to unlock vdp.  If quotas are enabled,
+	 * getinoquota() also requires exclusive lock to modify inode.
+	 */
+	ASSERT_VOP_LOCKED(vdp, "ufs_lookup1");
+	if ((nameiop == CREATE || nameiop == DELETE || nameiop == RENAME) &&
+	    (flags & (LOCKPARENT | ISLASTCN)) == (LOCKPARENT | ISLASTCN))
+		ASSERT_VOP_ELOCKED(vdp, "ufs_lookup2");
 #endif
 
 restart: