svn commit: r295616 - head/sys/fs/ext2fs

[Pedro F. Giffuni]

Author: pfg
Date: Sun Feb 14 19:52:50 2016
New Revision: 295616
URL: https://svnweb.freebsd.org/changeset/base/295616

Log:
  ext2fs:	Remove panics for rename() race conditions.
  
  Sync with r84642 from UFS:
  
  The panics are inappropriate because the IN_RENAME flag only fixes a
  few of the huge number of race conditions that can result in the
  source path becoming invalid even prior to the VOP_RENAME() call.
  
  Found accidentally while checking an issue from PVS Static Analysis.
  
  MFC after:	3 days

Modified:
  head/sys/fs/ext2fs/ext2_vnops.c

Modified: head/sys/fs/ext2fs/ext2_vnops.c
==============================================================================
--- head/sys/fs/ext2fs/ext2_vnops.c	Sun Feb 14 18:57:40 2016	(r295615)
+++ head/sys/fs/ext2fs/ext2_vnops.c	Sun Feb 14 19:52:50 2016	(r295616)
@@ -985,10 +985,10 @@ abortit:
 		dp = VTOI(fdvp);
 	} else {
 		/*
-		 * From name has disappeared.
+		 * From name has disappeared.  IN_RENAME is not sufficient
+		 * to protect against directory races due to timing windows,
+		 * so we can't panic here.
 		 */
-		if (doingdirectory)
-			panic("ext2_rename: lost dir entry");
 		vrele(ap->a_fvp);
 		return (0);
 	}
@@ -1003,8 +1003,11 @@ abortit:
 	 * rename.
 	 */
 	if (xp != ip) {
-		if (doingdirectory)
-			panic("ext2_rename: lost dir entry");
+		/*
+		 * From name resolves to a different inode.  IN_RENAME is
+		 * not sufficient protection against timing window races
+		 * so we can't panic here.
+		 */
 	} else {
 		/*
 		 * If the source is a directory with a