procfs: fix numbering in /proc/locks

The lock number in /proc/locks (first field) is implemented by a counter
(private field of struct seq_file) which is incremented at each call of
locks_show() and reset to 1 in locks_start() whatever the offset is.  It
should be reset according to the actual position in the list.  Because of
this, the numbering erratically restarts at 1 several times when reading a
long /proc/locks file.

Moreover, locks_show() can be called twice to print a single line thus
skipping a number.  The counter should be incremented in locks_next().

And last, pos is a loff_t, which can be bigger than a pointer, so we don't
use the pointer as an integer anymore, and allocate a loff_t instead.
Signed-off-by: NJerome Marchand <jmarchan@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/locks.c

@@ -2109,7 +2109,7 @@ EXPORT_SYMBOL_GPL(vfs_cancel_lock);
 #include <linux/seq_file.h>
 
 static void lock_get_status(struct seq_file *f, struct file_lock *fl,
-							int id, char *pfx)
+			    loff_t id, char *pfx)
 {
 	struct inode *inode = NULL;
 	unsigned int fl_pid;
@@ -2122,7 +2122,7 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 	if (fl->fl_file != NULL)
 		inode = fl->fl_file->f_path.dentry->d_inode;
 
-	seq_printf(f, "%d:%s ", id, pfx);
+	seq_printf(f, "%lld:%s ", id, pfx);
 	if (IS_POSIX(fl)) {
 		seq_printf(f, "%6s %s ",
 			     (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
@@ -2185,24 +2185,27 @@ static int locks_show(struct seq_file *f, void *v)
 
 	fl = list_entry(v, struct file_lock, fl_link);
 
-	lock_get_status(f, fl, (long)f->private, "");
+	lock_get_status(f, fl, *((loff_t *)f->private), "");
 
 	list_for_each_entry(bfl, &fl->fl_block, fl_block)
-		lock_get_status(f, bfl, (long)f->private, " ->");
+		lock_get_status(f, bfl, *((loff_t *)f->private), " ->");
 
-	f->private++;
 	return 0;
 }
 
 static void *locks_start(struct seq_file *f, loff_t *pos)
 {
+	loff_t *p = f->private;
+
 	lock_flocks();
-	f->private = (void *)1;
+	*p = (*pos + 1);
 	return seq_list_start(&file_lock_list, *pos);
 }
 
 static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
 {
+	loff_t *p = f->private;
+	++*p;
 	return seq_list_next(v, &file_lock_list, pos);
 }
 
@@ -2220,14 +2223,14 @@ static const struct seq_operations locks_seq_operations = {
 
 static int locks_open(struct inode *inode, struct file *filp)
 {
-	return seq_open(filp, &locks_seq_operations);
+	return seq_open_private(filp, &locks_seq_operations, sizeof(loff_t));
 }
 
 static const struct file_operations proc_locks_operations = {
 	.open		= locks_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= seq_release,
+	.release	= seq_release_private,
 };
 
 static int __init proc_locks_init(void)