[PATCH V5 12/13] namespaces: expose ns instance serial numbers in proc

[Serge E. Hallyn]

Quoting Richard Guy Briggs (rgb at redhat.com):
> Expose the namespace instace serial numbers in the proc filesystem at

(s/stac/stanc/)

> /proc/<pid>/ns/<ns>_snum.  The link text gives the serial number in hex.
> 
> "snum" was chosen instead of "seq" for consistency with inum and there are a
> number of other uses of "seq" in the namespace code.
> 
> Suggested-by: Serge E. Hallyn <serge at hallyn.com>

Acked-by: Serge Hallyn <serge.hallyn at canonical.com>

> Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
> ---
>  fs/proc/namespaces.c |   33 +++++++++++++++++++++++++--------
>  1 files changed, 25 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
> index 310da74..29c3909 100644
> --- a/fs/proc/namespaces.c
> +++ b/fs/proc/namespaces.c
> @@ -47,12 +47,15 @@ static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
>  	struct inode *inode = dentry->d_inode;
>  	const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns.ns_ops;
>  
> -	return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
> -		ns_ops->name, inode->i_ino);
> +	if (strstr(dentry->d_iname, "_snum"))
> +		return dynamic_dname(dentry, buffer, buflen, "%s_snum:[%llx]",
> +			ns_ops->name, ns_ops->snum(PROC_I(inode)->ns.ns));
> +	else
> +		return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
> +			ns_ops->name, inode->i_ino);
>  }
>  
> -const struct dentry_operations ns_dentry_operations =
> -{
> +const struct dentry_operations ns_dentry_operations = {
>  	.d_delete	= always_delete_dentry,
>  	.d_dname	= ns_dname,
>  };
> @@ -160,7 +163,10 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
>  	if (!ns)
>  		goto out_put_task;
>  
> -	snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns));
> +	if (strstr(dentry->d_iname, "_snum"))
> +		snprintf(name, sizeof(name), "%s_snum:[%llx]", ns_ops->name, ns_ops->snum(ns));
> +	else
> +		snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns));
>  	res = readlink_copy(buffer, buflen, name);
>  	ns_ops->put(ns);
>  out_put_task:
> @@ -210,16 +216,23 @@ static int proc_ns_dir_readdir(struct file *file, struct dir_context *ctx)
>  
>  	if (!dir_emit_dots(file, ctx))
>  		goto out;
> -	if (ctx->pos >= 2 + ARRAY_SIZE(ns_entries))
> +	if (ctx->pos >= 2 + 2 * ARRAY_SIZE(ns_entries))
>  		goto out;
>  	entry = ns_entries + (ctx->pos - 2);
>  	last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
>  	while (entry <= last) {
>  		const struct proc_ns_operations *ops = *entry;
> +		char name[50];
> +
>  		if (!proc_fill_cache(file, ctx, ops->name, strlen(ops->name),
>  				     proc_ns_instantiate, task, ops))
>  			break;
>  		ctx->pos++;
> +		snprintf(name, sizeof(name), "%s_snum", ops->name);
> +		if (!proc_fill_cache(file, ctx, name, strlen(name),
> +				     proc_ns_instantiate, task, ops))
> +			break;
> +		ctx->pos++;
>  		entry++;
>  	}
>  out:
> @@ -247,9 +260,13 @@ static struct dentry *proc_ns_dir_lookup(struct inode *dir,
>  
>  	last = &ns_entries[ARRAY_SIZE(ns_entries)];
>  	for (entry = ns_entries; entry < last; entry++) {
> -		if (strlen((*entry)->name) != len)
> +		char name[50];
> +
> +		snprintf(name, sizeof(name), "%s_snum", (*entry)->name);
> +		if (strlen((*entry)->name) != len && strlen(name) != len)
>  			continue;
> -		if (!memcmp(dentry->d_name.name, (*entry)->name, len))
> +		if (!memcmp(dentry->d_name.name, (*entry)->name, len)
> +		    || !memcmp(dentry->d_name.name, name, len))
>  			break;
>  	}
>  	if (entry == last)
> -- 
> 1.7.1