From: Robert Peterson <rpeterso@redhat.com>
Subject: [RHEL5.1][GFS2] Fixes related to bz 228540: gfs2 lockdump support
Date: Thu, 19 Apr 2007 10:02:30 -0500
Bugzilla: 228540
Message-Id: <46278486.7000804@redhat.com>
Changelog: [GFS2] lockdump support


It consolidates the following fixes that all relate to gfs2 kernel
lockdump support for bugzilla 228540:

1. The original fix for this bug, 228540.
2. The fix to use pid number and do pid lookups so we don't reference
   poisoned memory.  See comment #11 of the bugzilla.
3. The kallsyms patch that was accepted by the upstream kernel for
   2.6.22, currently appearing in Andrew Morton's -mm patchset.
4. The fix for 236008, where lockdump was causing a kernel gpf.
5. The fix I sent to cluster-devel yesterday regarding the fact that
   the debugfs files were not deleted upon failed mount attempts.
6. The implementation of Dave Teigland's suggestion to move the
   debugfs glock file into a separate directory (renamed) leaving
   room for future debugfs enhancements.

Regards,

Bob Peterson
Red Hat Cluster Suite

Signed-off-By: Bob Peterson <rpeterso@redhat.com>
--

diff -pur a/fs/gfs2/glock.c b/fs/gfs2/glock.c
--- a/fs/gfs2/glock.c	2007-04-18 13:46:52.000000000 -0500
+++ b/fs/gfs2/glock.c	2007-04-19 09:06:40.000000000 -0500
@@ -23,6 +23,10 @@
 #include <linux/module.h>
 #include <linux/rwsem.h>
 #include <asm/uaccess.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/kallsyms.h>
 
 #include "gfs2.h"
 #include "incore.h"
@@ -40,11 +44,19 @@ struct gfs2_gl_hash_bucket {
         struct hlist_head hb_list;
 };
 
+struct glock_iter {
+	int hash;                     /* hash bucket index         */
+	struct gfs2_sbd *sdp;         /* incore superblock         */
+	struct gfs2_glock *gl;        /* current glock struct      */
+	struct hlist_head *hb_list;   /* current hash bucket ptr   */
+	struct seq_file *seq;         /* sequence file for debugfs */
+	char string[512];             /* scratch space             */
+};
+
 typedef void (*glock_examiner) (struct gfs2_glock * gl);
 
 static int gfs2_dump_lockstate(struct gfs2_sbd *sdp);
-static int dump_glock(struct gfs2_glock *gl);
-static int dump_inode(struct gfs2_inode *ip);
+static int dump_glock(struct glock_iter *gi, struct gfs2_glock *gl);
 static void gfs2_glock_xmote_th(struct gfs2_holder *gh);
 static void gfs2_glock_drop_th(struct gfs2_glock *gl);
 static DECLARE_RWSEM(gfs2_umount_flush_sem);
@@ -54,6 +66,7 @@ static DECLARE_RWSEM(gfs2_umount_flush_s
 #define GFS2_GL_HASH_MASK       (GFS2_GL_HASH_SIZE - 1)
 
 static struct gfs2_gl_hash_bucket gl_hash_table[GFS2_GL_HASH_SIZE];
+static struct dentry *gfs2_root;
 
 /*
  * Despite what you might think, the numbers below are not arbitrary :-)
@@ -303,7 +316,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp,
 	atomic_set(&gl->gl_ref, 1);
 	gl->gl_state = LM_ST_UNLOCKED;
 	gl->gl_hash = hash;
-	gl->gl_owner = NULL;
+	gl->gl_owner_pid = 0;
 	gl->gl_ip = 0;
 	gl->gl_ops = glops;
 	gl->gl_req_gh = NULL;
@@ -367,7 +380,7 @@ void gfs2_holder_init(struct gfs2_glock 
 	INIT_LIST_HEAD(&gh->gh_list);
 	gh->gh_gl = gl;
 	gh->gh_ip = (unsigned long)__builtin_return_address(0);
-	gh->gh_owner = current;
+	gh->gh_owner_pid = current->pid;
 	gh->gh_state = state;
 	gh->gh_flags = flags;
 	gh->gh_error = 0;
@@ -654,7 +667,7 @@ static void gfs2_glmutex_lock(struct gfs
 	if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
 		list_add_tail(&gh.gh_list, &gl->gl_waiters1);
 	} else {
-		gl->gl_owner = current;
+		gl->gl_owner_pid = current->pid;
 		gl->gl_ip = (unsigned long)__builtin_return_address(0);
 		clear_bit(HIF_WAIT, &gh.gh_iflags);
 		smp_mb();
@@ -681,7 +694,7 @@ static int gfs2_glmutex_trylock(struct g
 	if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
 		acquired = 0;
 	} else {
-		gl->gl_owner = current;
+		gl->gl_owner_pid = current->pid;
 		gl->gl_ip = (unsigned long)__builtin_return_address(0);
 	}
 	spin_unlock(&gl->gl_spin);
@@ -699,7 +712,7 @@ static void gfs2_glmutex_unlock(struct g
 {
 	spin_lock(&gl->gl_spin);
 	clear_bit(GLF_LOCK, &gl->gl_flags);
-	gl->gl_owner = NULL;
+	gl->gl_owner_pid = 0;
 	gl->gl_ip = 0;
 	run_queue(gl);
 	BUG_ON(!spin_is_locked(&gl->gl_spin));
@@ -1097,18 +1110,32 @@ static int glock_wait_internal(struct gf
 }
 
 static inline struct gfs2_holder *
-find_holder_by_owner(struct list_head *head, struct task_struct *owner)
+find_holder_by_owner(struct list_head *head, pid_t pid)
 {
 	struct gfs2_holder *gh;
 
 	list_for_each_entry(gh, head, gh_list) {
-		if (gh->gh_owner == owner)
+		if (gh->gh_owner_pid == pid)
 			return gh;
 	}
 
 	return NULL;
 }
 
+static void print_dbg(struct glock_iter *gi, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	if (gi) {
+		vsprintf(gi->string, fmt, args);
+		seq_printf(gi->seq, gi->string);
+	}
+	else
+		vprintk(fmt, args);
+	va_end(args);
+}
+
 /**
  * add_to_queue - Add a holder to the wait queue (but look for recursion)
  * @gh: the holder structure to add
@@ -1120,24 +1147,24 @@ static void add_to_queue(struct gfs2_hol
 	struct gfs2_glock *gl = gh->gh_gl;
 	struct gfs2_holder *existing;
 
-	BUG_ON(!gh->gh_owner);
+	BUG_ON(!gh->gh_owner_pid);
 	if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags))
 		BUG();
 
-	existing = find_holder_by_owner(&gl->gl_holders, gh->gh_owner);
+	existing = find_holder_by_owner(&gl->gl_holders, gh->gh_owner_pid);
 	if (existing) {
 		print_symbol(KERN_WARNING "original: %s\n", existing->gh_ip);
-		printk(KERN_INFO "pid : %d\n", existing->gh_owner->pid);
+		printk(KERN_INFO "pid : %d\n", existing->gh_owner_pid);
 		printk(KERN_INFO "lock type : %d lock state : %d\n",
 				existing->gh_gl->gl_name.ln_type, existing->gh_gl->gl_state);
 		print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip);
-		printk(KERN_INFO "pid : %d\n", gh->gh_owner->pid);
+		printk(KERN_INFO "pid : %d\n", gh->gh_owner_pid);
 		printk(KERN_INFO "lock type : %d lock state : %d\n",
 				gl->gl_name.ln_type, gl->gl_state);
 		BUG();
 	}
 
-	existing = find_holder_by_owner(&gl->gl_waiters3, gh->gh_owner);
+	existing = find_holder_by_owner(&gl->gl_waiters3, gh->gh_owner_pid);
 	if (existing) {
 		print_symbol(KERN_WARNING "original: %s\n", existing->gh_ip);
 		print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip);
@@ -1841,6 +1868,15 @@ void gfs2_gl_hash_clear(struct gfs2_sbd 
  *  Diagnostic routines to help debug distributed deadlock
  */
 
+static void gfs2_print_symbol(struct glock_iter *gi, const char *fmt,
+                              unsigned long address)
+{
+	char buffer[KSYM_SYMBOL_LEN];
+
+	sprint_symbol(buffer, address);
+	print_dbg(gi, fmt, buffer);
+}
+
 /**
  * dump_holder - print information about a glock holder
  * @str: a string naming the type of holder
@@ -1849,31 +1885,37 @@ void gfs2_gl_hash_clear(struct gfs2_sbd 
  * Returns: 0 on success, -ENOBUFS when we run out of space
  */
 
-static int dump_holder(char *str, struct gfs2_holder *gh)
+static int dump_holder(struct glock_iter *gi, char *str,
+					   struct gfs2_holder *gh)
 {
 	unsigned int x;
-	int error = -ENOBUFS;
+	struct task_struct *gh_owner;
 
-	printk(KERN_INFO "  %s\n", str);
-	printk(KERN_INFO "    owner = %ld\n",
-		   (gh->gh_owner) ? (long)gh->gh_owner->pid : -1);
-	printk(KERN_INFO "    gh_state = %u\n", gh->gh_state);
-	printk(KERN_INFO "    gh_flags =");
+	print_dbg(gi, "  %s\n", str);
+	if (gh->gh_owner_pid) {
+		print_dbg(gi, "    owner = %ld ", (long)gh->gh_owner_pid);
+		gh_owner = find_task_by_pid(gh->gh_owner_pid);
+		if (gh_owner)
+			print_dbg(gi, "(%s)\n", gh_owner->comm);
+		else
+			print_dbg(gi, "(ended)\n");
+	} else
+		print_dbg(gi, "    owner = -1\n");
+	print_dbg(gi, "    gh_state = %u\n", gh->gh_state);
+	print_dbg(gi, "    gh_flags =");
 	for (x = 0; x < 32; x++)
 		if (gh->gh_flags & (1 << x))
-			printk(" %u", x);
-	printk(" \n");
-	printk(KERN_INFO "    error = %d\n", gh->gh_error);
-	printk(KERN_INFO "    gh_iflags =");
+			print_dbg(gi, " %u", x);
+	print_dbg(gi, " \n");
+	print_dbg(gi, "    error = %d\n", gh->gh_error);
+	print_dbg(gi, "    gh_iflags =");
 	for (x = 0; x < 32; x++)
 		if (test_bit(x, &gh->gh_iflags))
-			printk(" %u", x);
-	printk(" \n");
-	print_symbol(KERN_INFO "    initialized at: %s\n", gh->gh_ip);
-
-	error = 0;
+			print_dbg(gi, " %u", x);
+	print_dbg(gi, " \n");
+        gfs2_print_symbol(gi, "    initialized at: %s\n", gh->gh_ip);
 
-	return error;
+	return 0;
 }
 
 /**
@@ -1883,25 +1925,20 @@ static int dump_holder(char *str, struct
  * Returns: 0 on success, -ENOBUFS when we run out of space
  */
 
-static int dump_inode(struct gfs2_inode *ip)
+static int dump_inode(struct glock_iter *gi, struct gfs2_inode *ip)
 {
 	unsigned int x;
-	int error = -ENOBUFS;
 
-	printk(KERN_INFO "  Inode:\n");
-	printk(KERN_INFO "    num = %llu %llu\n",
-		    (unsigned long long)ip->i_num.no_formal_ino,
-		    (unsigned long long)ip->i_num.no_addr);
-	printk(KERN_INFO "    type = %u\n", IF2DT(ip->i_inode.i_mode));
-	printk(KERN_INFO "    i_flags =");
+	print_dbg(gi, "  Inode:\n");
+	print_dbg(gi, "    num = %llu/%llu\n",
+		    ip->i_num.no_formal_ino, ip->i_num.no_addr);
+	print_dbg(gi, "    type = %u\n", IF2DT(ip->i_inode.i_mode));
+	print_dbg(gi, "    i_flags =");
 	for (x = 0; x < 32; x++)
 		if (test_bit(x, &ip->i_flags))
-			printk(" %u", x);
-	printk(" \n");
-
-	error = 0;
-
-	return error;
+			print_dbg(gi, " %u", x);
+	print_dbg(gi, " \n");
+	return 0;
 }
 
 /**
@@ -1912,74 +1949,81 @@ static int dump_inode(struct gfs2_inode 
  * Returns: 0 on success, -ENOBUFS when we run out of space
  */
 
-static int dump_glock(struct gfs2_glock *gl)
+static int dump_glock(struct glock_iter *gi, struct gfs2_glock *gl)
 {
 	struct gfs2_holder *gh;
 	unsigned int x;
 	int error = -ENOBUFS;
+	struct task_struct *gl_owner;
 
 	spin_lock(&gl->gl_spin);
 
-	printk(KERN_INFO "Glock 0x%p (%u, %llu)\n", gl, gl->gl_name.ln_type,
-	       (unsigned long long)gl->gl_name.ln_number);
-	printk(KERN_INFO "  gl_flags =");
+	print_dbg(gi, "Glock 0x%p (%u, %llu)\n", gl, gl->gl_name.ln_type,
+		   (unsigned long long)gl->gl_name.ln_number);
+	print_dbg(gi, "  gl_flags =");
 	for (x = 0; x < 32; x++) {
 		if (test_bit(x, &gl->gl_flags))
-			printk(" %u", x);
+			print_dbg(gi, " %u", x);
 	}
-	printk(" \n");
-	printk(KERN_INFO "  gl_ref = %d\n", atomic_read(&gl->gl_ref));
-	printk(KERN_INFO "  gl_state = %u\n", gl->gl_state);
-	printk(KERN_INFO "  gl_owner = %s\n", gl->gl_owner->comm);
-	print_symbol(KERN_INFO "  gl_ip = %s\n", gl->gl_ip);
-	printk(KERN_INFO "  req_gh = %s\n", (gl->gl_req_gh) ? "yes" : "no");
-	printk(KERN_INFO "  req_bh = %s\n", (gl->gl_req_bh) ? "yes" : "no");
-	printk(KERN_INFO "  lvb_count = %d\n", atomic_read(&gl->gl_lvb_count));
-	printk(KERN_INFO "  object = %s\n", (gl->gl_object) ? "yes" : "no");
-	printk(KERN_INFO "  le = %s\n",
+	if (!test_bit(GLF_LOCK, &gl->gl_flags))
+		print_dbg(gi, " (unlocked)");
+	print_dbg(gi, " \n");
+	print_dbg(gi, "  gl_ref = %d\n", atomic_read(&gl->gl_ref));
+	print_dbg(gi, "  gl_state = %u\n", gl->gl_state);
+	if (gl->gl_owner_pid) {
+		gl_owner = find_task_by_pid(gl->gl_owner_pid);
+		if (gl_owner)
+			print_dbg(gi, "  gl_owner = pid %d (%s)\n",
+				  gl->gl_owner_pid, gl_owner->comm);
+		else
+			print_dbg(gi, "  gl_owner = %d (ended)\n",
+				  gl->gl_owner_pid);
+	} else
+		print_dbg(gi, "  gl_owner = -1\n");
+	print_dbg(gi, "  gl_ip = %lu\n", gl->gl_ip);
+	print_dbg(gi, "  req_gh = %s\n", (gl->gl_req_gh) ? "yes" : "no");
+	print_dbg(gi, "  req_bh = %s\n", (gl->gl_req_bh) ? "yes" : "no");
+	print_dbg(gi, "  lvb_count = %d\n", atomic_read(&gl->gl_lvb_count));
+	print_dbg(gi, "  object = %s\n", (gl->gl_object) ? "yes" : "no");
+	print_dbg(gi, "  le = %s\n",
 		   (list_empty(&gl->gl_le.le_list)) ? "no" : "yes");
-	printk(KERN_INFO "  reclaim = %s\n",
-		    (list_empty(&gl->gl_reclaim)) ? "no" : "yes");
+	print_dbg(gi, "  reclaim = %s\n",
+		   (list_empty(&gl->gl_reclaim)) ? "no" : "yes");
 	if (gl->gl_aspace)
-		printk(KERN_INFO "  aspace = 0x%p nrpages = %lu\n", gl->gl_aspace,
-		       gl->gl_aspace->i_mapping->nrpages);
+		print_dbg(gi, "  aspace = 0x%p nrpages = %lu\n", gl->gl_aspace,
+			   gl->gl_aspace->i_mapping->nrpages);
 	else
-		printk(KERN_INFO "  aspace = no\n");
-	printk(KERN_INFO "  ail = %d\n", atomic_read(&gl->gl_ail_count));
+		print_dbg(gi, "  aspace = no\n");
+	print_dbg(gi, "  ail = %d\n", atomic_read(&gl->gl_ail_count));
 	if (gl->gl_req_gh) {
-		error = dump_holder("Request", gl->gl_req_gh);
+		error = dump_holder(gi, "Request", gl->gl_req_gh);
 		if (error)
 			goto out;
 	}
 	list_for_each_entry(gh, &gl->gl_holders, gh_list) {
-		error = dump_holder("Holder", gh);
+		error = dump_holder(gi, "Holder", gh);
 		if (error)
 			goto out;
 	}
 	list_for_each_entry(gh, &gl->gl_waiters1, gh_list) {
-		error = dump_holder("Waiter1", gh);
-		if (error)
-			goto out;
-	}
-	list_for_each_entry(gh, &gl->gl_waiters2, gh_list) {
-		error = dump_holder("Waiter2", gh);
+		error = dump_holder(gi, "Waiter1", gh);
 		if (error)
 			goto out;
 	}
 	list_for_each_entry(gh, &gl->gl_waiters3, gh_list) {
-		error = dump_holder("Waiter3", gh);
+		error = dump_holder(gi, "Waiter3", gh);
 		if (error)
 			goto out;
 	}
 	if (gl->gl_ops == &gfs2_inode_glops && gl->gl_object) {
 		if (!test_bit(GLF_LOCK, &gl->gl_flags) &&
-		    list_empty(&gl->gl_holders)) {
-			error = dump_inode(gl->gl_object);
+			list_empty(&gl->gl_holders)) {
+			error = dump_inode(gi, gl->gl_object);
 			if (error)
 				goto out;
 		} else {
 			error = -ENOBUFS;
-			printk(KERN_INFO "  Inode: busy\n");
+			print_dbg(gi, "  Inode: busy\n");
 		}
 	}
 
@@ -2014,7 +2058,7 @@ static int gfs2_dump_lockstate(struct gf
 			if (gl->gl_sbd != sdp)
 				continue;
 
-			error = dump_glock(gl);
+			error = dump_glock(NULL, gl);
 			if (error)
 				break;
 		}
@@ -2043,3 +2087,189 @@ int __init gfs2_glock_init(void)
 	return 0;
 }
 
+static int gfs2_glock_iter_next(struct glock_iter *gi)
+{
+	read_lock(gl_lock_addr(gi->hash));
+	while (1) {
+		if (!gi->hb_list) {  /* If we don't have a hash bucket yet */
+			gi->hb_list = &gl_hash_table[gi->hash].hb_list;
+			if (hlist_empty(gi->hb_list)) {
+				read_unlock(gl_lock_addr(gi->hash));
+				gi->hash++;
+				read_lock(gl_lock_addr(gi->hash));
+				gi->hb_list = NULL;
+				if (gi->hash >= GFS2_GL_HASH_SIZE) {
+					read_unlock(gl_lock_addr(gi->hash));
+					return 1;
+				}
+				else
+					continue;
+			}
+			if (!hlist_empty(gi->hb_list)) {
+				gi->gl = list_entry(gi->hb_list->first,
+						    struct gfs2_glock,
+						    gl_list);
+			}
+		} else {
+			if (gi->gl->gl_list.next == NULL) {
+				read_unlock(gl_lock_addr(gi->hash));
+				gi->hash++;
+				read_lock(gl_lock_addr(gi->hash));
+				gi->hb_list = NULL;
+				continue;
+			}
+			gi->gl = list_entry(gi->gl->gl_list.next,
+					    struct gfs2_glock, gl_list);
+		}
+		if (gi->gl)
+			break;
+	}
+	read_unlock(gl_lock_addr(gi->hash));
+	return 0;
+}
+
+static void gfs2_glock_iter_free(struct glock_iter *gi)
+{
+	kfree(gi);
+}
+
+static struct glock_iter *gfs2_glock_iter_init(struct gfs2_sbd *sdp)
+{
+	struct glock_iter *gi;
+
+	gi = kmalloc(sizeof (*gi), GFP_KERNEL);
+	if (!gi)
+		return NULL;
+
+	gi->sdp = sdp;
+	gi->hash = 0;
+	gi->gl = NULL;
+	gi->hb_list = NULL;
+	gi->seq = NULL;
+	memset(gi->string, 0, sizeof(gi->string));
+
+	if (gfs2_glock_iter_next(gi)) {
+		gfs2_glock_iter_free(gi);
+		return NULL;
+	}
+
+	return gi;
+}
+
+static void *gfs2_glock_seq_start(struct seq_file *file, loff_t *pos)
+{
+	struct glock_iter *gi;
+	loff_t n = *pos;
+
+	gi = gfs2_glock_iter_init(file->private);
+	if (!gi)
+		return NULL;
+
+	while (n--) {
+		if (gfs2_glock_iter_next(gi)) {
+			gfs2_glock_iter_free(gi);
+			return NULL;
+		}
+	}
+
+	return gi;
+}
+
+static void *gfs2_glock_seq_next(struct seq_file *file, void *iter_ptr,
+				 loff_t *pos)
+{
+	struct glock_iter *gi = iter_ptr;
+
+	(*pos)++;
+
+	if (gfs2_glock_iter_next(gi)) {
+		gfs2_glock_iter_free(gi);
+		return NULL;
+	}
+
+	return gi;
+}
+
+static void gfs2_glock_seq_stop(struct seq_file *file, void *iter_ptr)
+{
+	/* nothing for now */
+}
+
+static int gfs2_glock_seq_show(struct seq_file *file, void *iter_ptr)
+{
+	struct glock_iter *gi = iter_ptr;
+
+	gi->seq = file;
+	dump_glock(gi, gi->gl);
+
+	return 0;
+}
+
+static struct seq_operations gfs2_glock_seq_ops = {
+	.start = gfs2_glock_seq_start,
+	.next  = gfs2_glock_seq_next,
+	.stop  = gfs2_glock_seq_stop,
+	.show  = gfs2_glock_seq_show,
+};
+
+static int gfs2_debugfs_open(struct inode *inode, struct file *file)
+{
+	struct seq_file *seq;
+	int ret;
+
+	ret = seq_open(file, &gfs2_glock_seq_ops);
+	if (ret)
+		return ret;
+
+	seq = file->private_data;
+	seq->private = inode->i_private;
+
+	return 0;
+}
+
+static const struct file_operations gfs2_debug_fops = {
+	.owner   = THIS_MODULE,
+	.open    = gfs2_debugfs_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = seq_release
+};
+
+int gfs2_create_debugfs_file(struct gfs2_sbd *sdp)
+{
+	sdp->debugfs_dir = debugfs_create_dir(sdp->sd_table_name, gfs2_root);
+	if (!sdp->debugfs_dir)
+		return -ENOMEM;
+	sdp->debugfs_dentry_glocks = debugfs_create_file("glocks",
+							 S_IFREG | S_IRUGO,
+							 sdp->debugfs_dir, sdp,
+							 &gfs2_debug_fops);
+	if (!sdp->debugfs_dentry_glocks)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp)
+{
+	if (sdp && sdp->debugfs_dir) {
+		if (sdp->debugfs_dentry_glocks) {
+			debugfs_remove(sdp->debugfs_dentry_glocks);
+			sdp->debugfs_dentry_glocks = NULL;
+		}
+		debugfs_remove(sdp->debugfs_dir);
+		sdp->debugfs_dir = NULL;
+	}
+}
+
+int gfs2_register_debugfs(void)
+{
+	gfs2_root = debugfs_create_dir("gfs2", NULL);
+	return gfs2_root ? 0 : -ENOMEM;
+}
+
+void gfs2_unregister_debugfs(void)
+{
+	debugfs_remove(gfs2_root);
+	gfs2_root = NULL;
+}
diff -pur a/fs/gfs2/glock.h b/fs/gfs2/glock.h
--- a/fs/gfs2/glock.h	2007-04-18 13:46:52.000000000 -0500
+++ b/fs/gfs2/glock.h	2007-04-18 15:06:50.000000000 -0500
@@ -38,7 +38,7 @@ static inline int gfs2_glock_is_locked_b
 	/* Look in glock's list of holders for one with current task as owner */
 	spin_lock(&gl->gl_spin);
 	list_for_each_entry(gh, &gl->gl_holders, gh_list) {
-		if (gh->gh_owner == current) {
+		if (gh->gh_owner_pid == current->pid) {
 			locked = 1;
 			break;
 		}
@@ -135,5 +135,9 @@ void gfs2_scand_internal(struct gfs2_sbd
 void gfs2_gl_hash_clear(struct gfs2_sbd *sdp, int wait);
 
 int __init gfs2_glock_init(void);
+int gfs2_create_debugfs_file(struct gfs2_sbd *sdp);
+void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp);
+int gfs2_register_debugfs(void);
+void gfs2_unregister_debugfs(void);
 
 #endif /* __GLOCK_DOT_H__ */
diff -pur a/fs/gfs2/incore.h b/fs/gfs2/incore.h
--- a/fs/gfs2/incore.h	2007-04-18 13:46:52.000000000 -0500
+++ b/fs/gfs2/incore.h	2007-04-19 09:08:18.000000000 -0500
@@ -130,7 +130,7 @@ struct gfs2_holder {
 	struct list_head gh_list;
 
 	struct gfs2_glock *gh_gl;
-	struct task_struct *gh_owner;
+	pid_t gh_owner_pid;
 	unsigned int gh_state;
 	unsigned gh_flags;
 
@@ -156,7 +156,7 @@ struct gfs2_glock {
 
 	unsigned int gl_state;
 	unsigned int gl_hash;
-	struct task_struct *gl_owner;
+	pid_t gl_owner_pid;
 	unsigned long gl_ip;
 	struct list_head gl_holders;
 	struct list_head gl_waiters1;	/* HIF_MUTEX */
@@ -613,6 +613,8 @@ struct gfs2_sbd {
 
 	unsigned long sd_last_warning;
 	struct vfsmount *sd_gfs2mnt;
+	struct dentry *debugfs_dir;    /* debugfs directory */
+	struct dentry *debugfs_dentry_glocks; /* for debugfs */
 };
 
 #endif /* __INCORE_DOT_H__ */
diff -pur a/fs/gfs2/main.c b/fs/gfs2/main.c
--- a/fs/gfs2/main.c	2007-04-18 08:55:40.000000000 -0500
+++ b/fs/gfs2/main.c	2007-04-18 18:04:44.000000000 -0500
@@ -104,6 +104,8 @@ static int __init init_gfs2_fs(void)
 	if (error)
 		goto fail_unregister;
 
+	gfs2_register_debugfs();
+
 	printk("GFS2 (built %s %s) installed\n", __DATE__, __TIME__);
 
 	return 0;
@@ -131,6 +133,7 @@ fail:
 
 static void __exit exit_gfs2_fs(void)
 {
+	gfs2_unregister_debugfs();
 	unregister_filesystem(&gfs2_fs_type);
 	unregister_filesystem(&gfs2meta_fs_type);
 
diff -pur a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
--- a/fs/gfs2/ops_fstype.c	2007-04-18 08:55:46.000000000 -0500
+++ b/fs/gfs2/ops_fstype.c	2007-04-18 15:01:39.000000000 -0500
@@ -705,6 +705,8 @@ static int fill_super(struct super_block
 	if (error)
 		goto fail;
 
+	gfs2_create_debugfs_file(sdp);
+
 	error = gfs2_sys_fs_add(sdp);
 	if (error)
 		goto fail;
@@ -769,6 +771,7 @@ fail_lm:
 fail_sys:
 	gfs2_sys_fs_del(sdp);
 fail:
+	gfs2_delete_debugfs_file(sdp);
 	kfree(sdp);
 	sb->s_fs_info = NULL;
 	return error;
@@ -914,6 +917,7 @@ error:
 
 static void gfs2_kill_sb(struct super_block *sb)
 {
+	gfs2_delete_debugfs_file(sb->s_fs_info);
 	kill_block_super(sb);
 }
 
diff -pur a/include/linux/kallsyms.h b/include/linux/kallsyms.h
--- a/include/linux/kallsyms.h	2006-09-19 22:42:06.000000000 -0500
+++ b/include/linux/kallsyms.h	2007-04-18 21:12:03.000000000 -0500
@@ -7,6 +7,8 @@
 
 
 #define KSYM_NAME_LEN 127
+#define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +	\
+			 2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1)
 
 #ifdef CONFIG_KALLSYMS
 /* Lookup the address for a symbol. Returns 0 if not found. */
@@ -18,7 +20,13 @@ const char *kallsyms_lookup(unsigned lon
 			    unsigned long *offset,
 			    char **modname, char *namebuf);
 
-/* Replace "%s" in format with address, if found */
+/* Look up a kernel symbol and return it in a text buffer. */
+extern int sprint_symbol(char *buffer, unsigned long address);
+
+int lookup_symbol_name(unsigned long addr, char *symname);
+int lookup_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name);
+
+/* Look up a kernel symbol and print it to the kernel messages. */
 extern void __print_symbol(const char *fmt, unsigned long address);
 
 #else /* !CONFIG_KALLSYMS */
@@ -36,6 +44,22 @@ static inline const char *kallsyms_looku
 	return NULL;
 }
 
+static inline int sprint_symbol(char *buffer, unsigned long addr)
+{
+	*buffer = '\0';
+	return 0;
+}
+
+static inline int lookup_symbol_name(unsigned long addr, char *symname)
+{
+	return -ERANGE;
+}
+
+static inline int lookup_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name)
+{
+	return -ERANGE;
+}
++
 /* Stupid that this does nothing, but I didn't create this mess. */
 #define __print_symbol(fmt, addr)
 #endif /*CONFIG_KALLSYMS*/
diff -pur a/kernel/kallsyms.c b/kernel/kallsyms.c
--- a/kernel/kallsyms.c	2007-04-18 08:55:41.000000000 -0500
+++ b/kernel/kallsyms.c	2007-04-18 21:02:41.000000000 -0500
@@ -230,29 +230,35 @@ const char *kallsyms_lookup(unsigned lon
 }
 
 /* Replace "%s" in format with address, or returns -errno. */
-void __print_symbol(const char *fmt, unsigned long address)
+int sprint_symbol(char *buffer, unsigned long address)
 {
 	char *modname;
 	const char *name;
 	unsigned long offset, size;
 	char namebuf[KSYM_NAME_LEN+1];
-	char buffer[sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +
-		    2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1];
 
 	name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
-
 	if (!name)
-		sprintf(buffer, "0x%lx", address);
+		return sprintf(buffer, "0x%lx", address);
 	else {
 		if (modname)
-			sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
-				size, modname);
+			return sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
+ 				size, modname);
 		else
-			sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
+			return sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 	}
-	printk(fmt, buffer);
 }
 
+/* Look up a kernel symbol and print it to the kernel messages. */
+void __print_symbol(const char *fmt, unsigned long address)
+{
+	char buffer[KSYM_SYMBOL_LEN];
+
+	sprint_symbol(buffer, address);
+
+	printk(fmt, buffer);
+}
+ 
 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 struct kallsym_iter
 {
@@ -418,3 +424,4 @@ static int __init kallsyms_init(void)
 __initcall(kallsyms_init);
 
 EXPORT_SYMBOL(__print_symbol);
+EXPORT_SYMBOL_GPL(sprint_symbol);