[Devel] [RFC][PATCH 2/2] introduce proc_mnt for pid_ns
Dave Hansen
hansendc at us.ibm.com
Tue Feb 20 11:00:56 PST 2007
The following patch completes the removal of the global proc_mnt.
It fetches the mnt on which to do dentry invalidations from the
pid_namespace in which the task appears.
For now, there is only one pid namespace in mainline so this is
straightforward. In the -lxc tree we'll have to do something
more complex.
Note that the new proc_compare_super() enforces the "one proc sb
per pid_namespace" limit.
/proc currently has some special code to make sure that the root
directory gets set up correctly. It proc_mnt variable in order
to find its way to the root inode.
Now that we don't have the global proc_mnt, we can fill in the
root inode's data in proc_fill_super(), where it takes a wee bit
less work than in proc_get_sb().
Signed-off-by: Dave Hansen <haveblue at us.ibm.com>
---
lxc-dave/fs/proc/base.c | 32 +++++++++++++++++++++-
lxc-dave/fs/proc/inode.c | 10 +++++--
lxc-dave/fs/proc/root.c | 46 ++++++++++++++++++++-------------
lxc-dave/include/linux/pid_namespace.h | 1
lxc-dave/include/linux/proc_fs.h | 1
5 files changed, 67 insertions(+), 23 deletions(-)
diff -puN fs/proc/base.c~A3-remove-proc_mnt-1 fs/proc/base.c
--- lxc/fs/proc/base.c~A3-remove-proc_mnt-1 2007-02-20 10:07:28.000000000 -0800
+++ lxc-dave/fs/proc/base.c 2007-02-20 10:07:29.000000000 -0800
@@ -71,6 +71,7 @@
#include <linux/seccomp.h>
#include <linux/cpuset.h>
#include <linux/audit.h>
+#include <linux/pid_namespace.h>
#include <linux/poll.h>
#include <linux/nsproxy.h>
#include <linux/oom.h>
@@ -2001,9 +2002,11 @@ static const struct inode_operations pro
};
/**
- * proc_flush_task - Remove dcache entries for @task from the /proc dcache.
+ * proc_flush_task_from_pid_ns - Remove dcache entries for @task
+ * from the /proc dcache.
*
* @task: task that should be flushed.
+ * @pid_ns: pid_namespace in which that task appears
*
* Looks in the dcache for
* /proc/@pid
@@ -2021,11 +2024,23 @@ static const struct inode_operations pro
* that no dcache entries will exist at process exit time it
* just makes it very unlikely that any will persist.
*/
-void proc_flush_task(struct task_struct *task)
+void proc_flush_task_from_pid_ns(struct task_struct *task,
+ struct pid_namespace* pid_ns)
{
struct dentry *dentry, *leader, *dir;
char buf[PROC_NUMBUF];
struct qstr name;
+ struct vfsmount *proc_mnt;
+
+ /*
+ * It is possible that no /procs have been instantiated
+ * for this particular pid namespace, or that we're trying
+ * to flush for a task without a pid_ns, like a kernel
+ * thread.
+ */
+ if (!pid_ns || !pid_ns->proc_mnt)
+ return;
+ proc_mnt = pid_ns->proc_mnt;
name.name = buf;
name.len = snprintf(buf, sizeof(buf), "%d", task->pid);
@@ -2067,6 +2082,19 @@ out:
return;
}
+void proc_flush_task(struct task_struct *task)
+{
+ struct pid_namespace *pid_ns = NULL;
+ /*
+ * Right now, tasks only appear in their own pid_ns.
+ * With containers this function will change to a loop
+ * over all pid_ns's in which the task appears.
+ */
+ if (task->nsproxy)
+ pid_ns = task->nsproxy->pid_ns;
+ proc_flush_task_from_pid_ns(task, pid_ns);
+}
+
static struct dentry *proc_pid_instantiate(struct inode *dir,
struct dentry * dentry,
struct task_struct *task, void *ptr)
diff -puN fs/proc/inode.c~A3-remove-proc_mnt-1 fs/proc/inode.c
--- lxc/fs/proc/inode.c~A3-remove-proc_mnt-1 2007-02-20 10:07:28.000000000 -0800
+++ lxc-dave/fs/proc/inode.c 2007-02-20 10:07:29.000000000 -0800
@@ -67,8 +67,6 @@ static void proc_delete_inode(struct ino
clear_inode(inode);
}
-struct vfsmount *proc_mnt;
-
static void proc_read_inode(struct inode * inode)
{
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
@@ -184,6 +182,8 @@ out_mod:
int proc_fill_super(struct super_block *s, void *data, int silent)
{
+ struct pid_namespace *pid_ns = data;
+ struct proc_inode *ei;
struct inode * root_inode;
s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
@@ -192,6 +192,7 @@ int proc_fill_super(struct super_block *
s->s_magic = PROC_SUPER_MAGIC;
s->s_op = &proc_sops;
s->s_time_gran = 1;
+ s->s_fs_info = pid_ns;
root_inode = proc_get_inode(s, PROC_ROOT_INO, &proc_root);
if (!root_inode)
@@ -201,6 +202,11 @@ int proc_fill_super(struct super_block *
s->s_root = d_alloc_root(root_inode);
if (!s->s_root)
goto out_no_root;
+ /* Seed the root directory with a pid so it doesn't need
+ * to be special in base.c.
+ */
+ ei = PROC_I(root_inode);
+ ei->pid = find_get_pid(1);
return 0;
out_no_root:
diff -puN fs/proc/root.c~A3-remove-proc_mnt-1 fs/proc/root.c
--- lxc/fs/proc/root.c~A3-remove-proc_mnt-1 2007-02-20 10:07:28.000000000 -0800
+++ lxc-dave/fs/proc/root.c 2007-02-20 10:07:29.000000000 -0800
@@ -18,26 +18,42 @@
#include <linux/bitops.h>
#include <linux/smp_lock.h>
#include <linux/mount.h>
+#include <linux/pid_namespace.h>
#include "internal.h"
struct proc_dir_entry *proc_net, *proc_net_stat, *proc_bus, *proc_root_fs, *proc_root_driver;
+static int proc_test_sb(struct super_block *s, void *data)
+{
+ struct pid_namespace *pid_ns = data;
+ if (s->s_fs_info == pid_ns)
+ return 1;
+ return 0;
+}
+
+static int proc_set_sb(struct super_block *s, void *data)
+{
+ int ret;
+ ret = set_anon_super(s, NULL);
+ if (!ret)
+ ret = proc_fill_super(s, data, 0);
+ return ret;
+}
+
static int proc_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
- if (proc_mnt) {
- /* Seed the root directory with a pid so it doesn't need
- * to be special in base.c. I would do this earlier but
- * the only task alive when /proc is mounted the first time
- * is the init_task and it doesn't have any pids.
- */
- struct proc_inode *ei;
- ei = PROC_I(proc_mnt->mnt_sb->s_root->d_inode);
- if (!ei->pid)
- ei->pid = find_get_pid(1);
- }
- return get_sb_single(fs_type, flags, data, proc_fill_super, mnt);
+ struct super_block *s;
+
+ s = sget(fs_type, proc_test_sb, proc_set_sb, current->nsproxy->pid_ns);
+ if (IS_ERR(s))
+ return PTR_ERR(s);
+ if (!current->nsproxy->pid_ns->proc_mnt)
+ current->nsproxy->pid_ns->proc_mnt = mnt;
+
+ do_remount_sb(s, flags, data, 0);
+ return simple_set_mnt(mnt, s);
}
static struct file_system_type proc_fs_type = {
@@ -54,12 +70,6 @@ void __init proc_root_init(void)
err = register_filesystem(&proc_fs_type);
if (err)
return;
- proc_mnt = kern_mount(&proc_fs_type);
- err = PTR_ERR(proc_mnt);
- if (IS_ERR(proc_mnt)) {
- unregister_filesystem(&proc_fs_type);
- return;
- }
proc_misc_init();
proc_net = proc_mkdir("net", NULL);
proc_net_stat = proc_mkdir("net/stat", NULL);
diff -puN include/linux/pid_namespace.h~A3-remove-proc_mnt-1 include/linux/pid_namespace.h
--- lxc/include/linux/pid_namespace.h~A3-remove-proc_mnt-1 2007-02-20 10:07:28.000000000 -0800
+++ lxc-dave/include/linux/pid_namespace.h 2007-02-20 10:07:29.000000000 -0800
@@ -20,6 +20,7 @@ struct pid_namespace {
struct pidmap pidmap[PIDMAP_ENTRIES];
int last_pid;
struct task_struct *child_reaper;
+ struct vfsmount *proc_mnt;
};
extern struct pid_namespace init_pid_ns;
diff -puN include/linux/proc_fs.h~A3-remove-proc_mnt-1 include/linux/proc_fs.h
--- lxc/include/linux/proc_fs.h~A3-remove-proc_mnt-1 2007-02-20 10:07:28.000000000 -0800
+++ lxc-dave/include/linux/proc_fs.h 2007-02-20 10:07:29.000000000 -0800
@@ -129,7 +129,6 @@ extern struct proc_dir_entry *create_pro
struct proc_dir_entry *parent);
extern void remove_proc_entry(const char *name, struct proc_dir_entry *parent);
-extern struct vfsmount *proc_mnt;
extern int proc_fill_super(struct super_block *,void *,int);
extern struct inode *proc_get_inode(struct super_block *, unsigned int, struct proc_dir_entry *);
_
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