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Date:      Sat, 22 Nov 2008 13:11:11 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r185170 - head/sys/ufs/ufs
Message-ID:  <200811221311.mAMDBBU8018510@svn.freebsd.org>
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Author: kib
Date: Sat Nov 22 13:11:11 2008
New Revision: 185170
URL: http://svn.freebsd.org/changeset/base/185170

Log:
  Busy ufs filesystem around block of code that does ".." lookup. Since
  mnt_lock is before lock of any vnode on the mp, it uses LK_NOWAIT. Since
  MNTK_UNMOUNT may be transient, pdp lock is dropped when vfs_busy()
  failed, and operation is retried after some time. This way, ffs_vget()
  is not called on the mp that may be in the process of being destroyed by
  unmount.
  
  Check for the VI_DOOMED flag on pdp after its lock is reacquired, to
  better detect some situations where directory containing ".."
  entry is removed during the lookup.
  
  Reviewed by:	tegge, attilio (previous version)
  Tested by:	pho
  MFC after:	1 month

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

Modified: head/sys/ufs/ufs/ufs_lookup.c
==============================================================================
--- head/sys/ufs/ufs/ufs_lookup.c	Sat Nov 22 12:36:15 2008	(r185169)
+++ head/sys/ufs/ufs/ufs_lookup.c	Sat Nov 22 13:11:11 2008	(r185170)
@@ -157,6 +157,8 @@ ufs_lookup(ap)
 	int nameiop = cnp->cn_nameiop;
 	ino_t ino;
 	int ltype;
+	int pdoomed;
+	struct mount *mp;
 
 	bp = NULL;
 	slotoffset = -1;
@@ -578,9 +580,32 @@ found:
 	pdp = vdp;
 	if (flags & ISDOTDOT) {
 		ltype = VOP_ISLOCKED(pdp);
+		mp = pdp->v_mount;
+		for (;;) {
+			error = vfs_busy(mp, MBF_NOWAIT);
+			if (error == 0)
+				break;
+			VOP_UNLOCK(pdp, 0);
+			pause("ufs_dd", 1);
+			vn_lock(pdp, ltype | LK_RETRY);
+			VI_LOCK(pdp);
+			pdoomed = pdp->v_iflag & VI_DOOMED;
+			VI_UNLOCK(pdp);
+			if (pdoomed)
+				return (ENOENT);
+		}
 		VOP_UNLOCK(pdp, 0);	/* race to get the inode */
-		error = VFS_VGET(pdp->v_mount, ino, cnp->cn_lkflags, &tdp);
+		error = VFS_VGET(mp, ino, cnp->cn_lkflags, &tdp);
+		vfs_unbusy(mp);
 		vn_lock(pdp, ltype | LK_RETRY);
+		VI_LOCK(pdp);
+		pdoomed = pdp->v_iflag & VI_DOOMED;
+		VI_UNLOCK(pdp);
+		if (pdoomed) {
+			if (error == 0)
+				vput(tdp);
+			error = ENOENT;
+		}
 		if (error)
 			return (error);
 		*vpp = tdp;

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