[Devel] [PATCH 16/17] Pid-NS(V3) Remove proc_mnts use for killing inodes

[sukadev at us.ibm.com]

From: sukadev at linux.vnet.ibm.com
Subject: [PATCH 16/17] Pid-NS(V3) Remove proc_mnts use for killing inodes


We use proc_mnt as a shortcut to find a superblock on which
to go killing /proc inodes.  This will break if we ever have
more than one /proc superblock.  So, use the superblock list
to go find each of the /proc sb's and kill inodes on each
superblock.

This does introduce an extra lock grab from what was there
before, but the list should be only 1 long 99% of the time,
and we don't exactly remove proc entries in hot paths.  Note
that this *isn't* the path that we use to get rid of the
actual /proc pid entries.  Those are a different beast.

Changelog:

	2.6.22-rc4-mm2-pidns1:
	- [Sukadev Bhattiprolu] Initialize proc_fs_type.fs_supers.

Signed-off-by: Dave Hansen <haveblue at us.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>
---
 fs/proc/generic.c |   28 +++++++++++++++++++++++-----
 fs/proc/root.c    |    1 +
 2 files changed, 24 insertions(+), 5 deletions(-)

Index: lx26-22-rc4-mm2/fs/proc/generic.c
===================================================================
--- lx26-22-rc4-mm2.orig/fs/proc/generic.c	2007-06-15 17:21:28.000000000 -0700
+++ lx26-22-rc4-mm2/fs/proc/generic.c	2007-06-15 18:16:57.000000000 -0700
@@ -555,13 +555,10 @@ static int proc_register(struct proc_dir
 	return 0;
 }
 
-/*
- * Kill an inode that got unregistered..
- */
-static void proc_kill_inodes(struct proc_dir_entry *de)
+static void proc_kill_inodes_sb(struct proc_dir_entry *de,
+				struct super_block *sb)
 {
 	struct list_head *p;
-	struct super_block *sb = proc_mnt->mnt_sb;
 
 	/*
 	 * Actually it's a partial revoke().
@@ -585,6 +582,27 @@ static void proc_kill_inodes(struct proc
 	file_list_unlock();
 }
 
+/*
+ * Kill an inode that got unregistered..
+ */
+static void proc_kill_inodes(struct proc_dir_entry *de)
+{
+	struct list_head *l;
+	struct file_system_type *procfs;
+
+	procfs = get_fs_type("proc");
+	if (!procfs)
+		return;
+
+	spin_lock(&sb_lock);
+	list_for_each(l, &procfs->fs_supers) {
+		struct super_block *sb;
+		sb = list_entry(l, struct super_block, s_instances);
+		proc_kill_inodes_sb(de, sb);
+	}
+	spin_unlock(&sb_lock);
+}
+
 static struct proc_dir_entry *proc_create(struct proc_dir_entry **parent,
 					  const char *name,
 					  mode_t mode,
Index: lx26-22-rc4-mm2/fs/proc/root.c
===================================================================
--- lx26-22-rc4-mm2.orig/fs/proc/root.c	2007-06-15 17:21:28.000000000 -0700
+++ lx26-22-rc4-mm2/fs/proc/root.c	2007-06-15 18:16:57.000000000 -0700
@@ -44,6 +44,7 @@ static struct file_system_type proc_fs_t
 	.name		= "proc",
 	.get_sb		= proc_get_sb,
 	.kill_sb	= kill_anon_super,
+	.fs_supers      = LIST_HEAD_INIT(proc_fs_type.fs_supers),
 };
 
 void __init proc_root_init(void)

-- 
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