Re: [PATCH 2/2] Replace pid_t in autofs with struct pid reference

[Ian Kent <raven@themaw.net>]

On Fri, 2007-03-16 at 15:44 +0100, Cedric Le Goater wrote:
> > How about you send over the autofs4 bit and I'll have a look (the autofs
> > patch looked fine). That would save me a bit of time and if there are
> > any changes needed I can send an updated patch for you guys to review. I
> > don't think autofs4 uses pids differently, in principle, than autofs so
> > it "should" be straight forward.
> 
> Here's the latest.

That looks OK to me, assuming the "find_get_pid" and friends do what
they suggest, but I'll give it a closer look tomorrow.

A ref count is used here, what affect does that have on a thread (or
process) that may go away (or be summarily killed) without umounting the
mount?

Thanks
Ian

> 
> thanks,
> 
> C.
> 
> From: Sukadev Bhattiprolu <sukadev@us.ibm.com>
> 
> Subject: Replace pid_t in autofs4 with struct pid reference.
> 
> Make autofs4 container-friendly by caching struct pid reference rather
> than pid_t and using pid_nr() to retreive a task's pid_t.
> 
> ChangeLog:
> 	- Fix Eric Biederman's comments - Use find_get_pid() to hold a
> 	  reference to oz_pgrp and release while unmounting; separate out
> 	  changes to autofs and autofs4.
> 	- Also rollback my earlier change to autofs_wait_queue (pid and tgid
> 	  in the wait queue are just used to write to a userspace daemon's
> 	  pipe).
>         - Fix Cedric's comments: retain old prototype of parse_options()
>           and move necessary change to its caller.
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
> Cc: Cedric Le Goater <clg@fr.ibm.com>
> Cc: Dave Hansen <haveblue@us.ibm.com>
> Cc: Serge Hallyn <serue@us.ibm.com>
> Cc: Eric Biederman <ebiederm@xmission.com>
> Cc: containers@lists.osdl.org
> 
> ---
>  fs/autofs4/autofs_i.h |    6 +++---
>  fs/autofs4/inode.c    |   21 ++++++++++++++++-----
>  fs/autofs4/root.c     |    3 ++-
>  fs/autofs4/waitq.c    |    4 ++--
>  4 files changed, 23 insertions(+), 11 deletions(-)
> 
> Index: 2.6.20/fs/autofs4/autofs_i.h
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/autofs_i.h
> +++ 2.6.20/fs/autofs4/autofs_i.h
> @@ -35,7 +35,7 @@
>  /* #define DEBUG */
>  
>  #ifdef DEBUG
> -#define DPRINTK(fmt,args...) do { printk(KERN_DEBUG "pid %d: %s: " fmt "\n" , current->pid , __FUNCTION__ , ##args); } while(0)
> +#define DPRINTK(fmt,args...) do { printk(KERN_DEBUG "pid %d: %s: " fmt "\n" , pid_nr(task_pid(current)), __FUNCTION__ , ##args); } while(0)
>  #else
>  #define DPRINTK(fmt,args...) do {} while(0)
>  #endif
> @@ -96,7 +96,7 @@ struct autofs_sb_info {
>  	u32 magic;
>  	int pipefd;
>  	struct file *pipe;
> -	pid_t oz_pgrp;
> +	struct pid *oz_pgrp;
>  	int catatonic;
>  	int version;
>  	int sub_version;
> @@ -127,7 +127,7 @@ static inline struct autofs_info *autofs
>     filesystem without "magic".) */
>  
>  static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
> -	return sbi->catatonic || process_group(current) == sbi->oz_pgrp;
> +	return sbi->catatonic || task_pgrp(current) == sbi->oz_pgrp;
>  }
>  
>  /* Does a dentry have some pending activity? */
> Index: 2.6.20/fs/autofs4/inode.c
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/inode.c
> +++ 2.6.20/fs/autofs4/inode.c
> @@ -163,6 +163,8 @@ void autofs4_kill_sb(struct super_block 
>  	if ( !sbi->catatonic )
>  		autofs4_catatonic_mode(sbi); /* Free wait queues, close pipe */
>  
> +	put_pid(sbi->oz_pgrp);
> +
>  	/* Clean up and release dangling references */
>  	autofs4_force_release(sbi);
>  
> @@ -181,7 +183,7 @@ static int autofs4_show_options(struct s
>  		return 0;
>  
>  	seq_printf(m, ",fd=%d", sbi->pipefd);
> -	seq_printf(m, ",pgrp=%d", sbi->oz_pgrp);
> +	seq_printf(m, ",pgrp=%d", pid_nr(sbi->oz_pgrp));
>  	seq_printf(m, ",timeout=%lu", sbi->exp_timeout/HZ);
>  	seq_printf(m, ",minproto=%d", sbi->min_proto);
>  	seq_printf(m, ",maxproto=%d", sbi->max_proto);
> @@ -311,6 +313,7 @@ int autofs4_fill_super(struct super_bloc
>  	int pipefd;
>  	struct autofs_sb_info *sbi;
>  	struct autofs_info *ino;
> +	pid_t pgid;
>  
>  	sbi = kmalloc(sizeof(*sbi), GFP_KERNEL);
>  	if (!sbi)
> @@ -325,7 +328,6 @@ int autofs4_fill_super(struct super_bloc
>  	sbi->pipe = NULL;
>  	sbi->catatonic = 1;
>  	sbi->exp_timeout = 0;
> -	sbi->oz_pgrp = process_group(current);
>  	sbi->sb = s;
>  	sbi->version = 0;
>  	sbi->sub_version = 0;
> @@ -361,7 +363,7 @@ int autofs4_fill_super(struct super_bloc
>  
>  	/* Can this call block? */
>  	if (parse_options(data, &pipefd, &root_inode->i_uid, &root_inode->i_gid,
> -				&sbi->oz_pgrp, &sbi->type, &sbi->min_proto,
> +				&pgid, &sbi->type, &sbi->min_proto,
>  				&sbi->max_proto)) {
>  		printk("autofs: called with bogus options\n");
>  		goto fail_dput;
> @@ -389,12 +391,19 @@ int autofs4_fill_super(struct super_bloc
>  		sbi->version = sbi->max_proto;
>  	sbi->sub_version = AUTOFS_PROTO_SUBVERSION;
>  
> -	DPRINTK("pipe fd = %d, pgrp = %u", pipefd, sbi->oz_pgrp);
> +	DPRINTK("pipe fd = %d, pgrp = %u", pipefd, pgid);
> +
> +	sbi->oz_pgrp = find_get_pid(pgid);
> +	if (!sbi->oz_pgrp) {
> +		printk("autofs: could not find process group %d\n", pgid);
> +		goto fail_dput;
> +	}
> +
>  	pipe = fget(pipefd);
>  	
>  	if (!pipe) {
>  		printk("autofs: could not open pipe file descriptor\n");
> -		goto fail_dput;
> +		goto fail_put_pid;
>  	}
>  	if (!pipe->f_op || !pipe->f_op->write)
>  		goto fail_fput;
> @@ -415,6 +424,8 @@ fail_fput:
>  	printk("autofs: pipe file descriptor does not contain proper ops\n");
>  	fput(pipe);
>  	/* fall through */
> +fail_put_pid:
> +	put_pid(sbi->oz_pgrp);
>  fail_dput:
>  	dput(root);
>  	goto fail_free;
> Index: 2.6.20/fs/autofs4/root.c
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/root.c
> +++ 2.6.20/fs/autofs4/root.c
> @@ -495,7 +495,8 @@ static struct dentry *autofs4_lookup(str
>  	oz_mode = autofs4_oz_mode(sbi);
>  
>  	DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
> -		 current->pid, process_group(current), sbi->catatonic, oz_mode);
> +		 pid_nr(task_pid(current)), process_group(current),
> +		 sbi->catatonic, oz_mode);
>  
>  	/*
>  	 * Mark the dentry incomplete, but add it. This is needed so
> Index: 2.6.20/fs/autofs4/waitq.c
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/waitq.c
> +++ 2.6.20/fs/autofs4/waitq.c
> @@ -292,8 +292,8 @@ int autofs4_wait(struct autofs_sb_info *
>  		wq->ino = autofs4_get_ino(sbi);
>  		wq->uid = current->uid;
>  		wq->gid = current->gid;
> -		wq->pid = current->pid;
> -		wq->tgid = current->tgid;
> +		wq->pid = pid_nr(task_pid(current));
> +		wq->tgid = pid_nr(task_tgid(current));
>  		wq->status = -EINTR; /* Status return if interrupted */
>  		atomic_set(&wq->wait_ctr, 2);
>  		mutex_unlock(&sbi->wq_mutex);