linux-kernel - [PATCH] procfs: fix numbering in /proc/locks

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Message-ID: <4CA0B4A5.1090701@redhat.com>
Date:	Mon, 27 Sep 2010 17:13:41 +0200
From:	Jerome Marchand <jmarchan@...hat.com>
To:	Matthew Wilcox <matthew@....cx>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pavel Emelianov <xemul@...nvz.org>
Subject: [PATCH] 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(). Currently it is reset each time locks_start() is called,
that is each time we call the read() syscall on /proc/locks. Because of
that, the numbering erratically restarts at 1 several times when reading
a long /proc/locks file.
We want the counter to be initialized at opening time and then never
reset until we close the file. Fortunately, seq_open() memzeros the
seq_file structure, so we can just drop the reset in locks_start() and
move the increment the counter before actually printing the line so the
numbering still starts at 1.

Signed-off-by: Jerome Marchand <jmarchan@...hat.com>
---
diff --git a/fs/locks.c b/fs/locks.c
index ab24d49..a5eab5e 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2161,19 +2161,18 @@ static int locks_show(struct seq_file *f, void *v)

 	fl = list_entry(v, struct file_lock, fl_link);

+	f->private++;
 	lock_get_status(f, fl, (long)f->private, "");

 	list_for_each_entry(bfl, &fl->fl_block, fl_block)
 		lock_get_status(f, bfl, (long)f->private, " ->");

-	f->private++;
 	return 0;
 }

 static void *locks_start(struct seq_file *f, loff_t *pos)
 {
 	lock_kernel();
-	f->private = (void *)1;
 	return seq_list_start(&file_lock_list, *pos);
 }

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