From: Wendy Cheng <wcheng@redhat.com>
Subject: [RHEL5.2 PATCH] 03/02 NFS fix - gfs2_drevalidate panic
Date: Thu, 01 Mar 2007 16:02:09 -0500
Bugzilla: 229349
Message-Id: <45E73F51.40802@redhat.com>
Changelog: [gfs2] NFS cause recursive locking


Bugzilla 229349

Glock assertion failure found in '07 NFS connectathon. One of the NFSDs 
was doing a "readdirplus" procedure call. It passed the logic into 
gfs2_readdir() where the call obtained its directory inode glock. It 
then subsequently tried to construct the filehandle based on the 
contents of the directory listing that ended up requiring the very same 
lock again. This crashed RHEL5 if "ls" command was issued from NFS clients.

-- Wendy


--- linux-0227/fs/gfs2/ops_dentry.c	2007-02-27 17:26:07.000000000 -0500
+++ linux/fs/gfs2/ops_dentry.c	2007-02-27 17:33:56.000000000 -0500
@@ -46,6 +46,7 @@ static int gfs2_drevalidate(struct dentr
 	struct gfs2_inum inum;
 	unsigned int type;
 	int error;
+	int had_lock=0;
 
 	if (inode && is_bad_inode(inode))
 		goto invalid;
@@ -53,9 +54,12 @@ static int gfs2_drevalidate(struct dentr
 	if (sdp->sd_args.ar_localcaching)
 		goto valid;
 
-	error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
-	if (error)
-		goto fail;
+	had_lock = gfs2_glock_is_locked_by_me(dip->i_gl);
+	if (!had_lock) {
+		error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
+		if (error)
+			goto fail;
+	} 
 
 	error = gfs2_dir_search(parent->d_inode, &dentry->d_name, &inum, &type);
 	switch (error) {
@@ -82,13 +86,15 @@ static int gfs2_drevalidate(struct dentr
 	}
 
 valid_gunlock:
-	gfs2_glock_dq_uninit(&d_gh);
+	if (!had_lock)
+		gfs2_glock_dq_uninit(&d_gh);
 valid:
 	dput(parent);
 	return 1;
 
 invalid_gunlock:
-	gfs2_glock_dq_uninit(&d_gh);
+	if (!had_lock)
+		gfs2_glock_dq_uninit(&d_gh);
 invalid:
 	if (inode && S_ISDIR(inode->i_mode)) {
 		if (have_submounts(dentry))