linux-kernel - Re: [RFC v9][PATCH 05/13] Dump memory address space

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Date:	Tue, 11 Nov 2008 18:53:23 -0500
From:	Oren Laadan <orenl@...columbia.edu>
To:	"Serge E. Hallyn" <serue@...ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...l.org>,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-api@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFC v9][PATCH 05/13] Dump memory address space



Serge E. Hallyn wrote:
> Quoting Oren Laadan (orenl@...columbia.edu):
>> +/**
>> + * cr_fill_fname - return pathname of a given file
>> + * @path: path name
>> + * @root: relative root
>> + * @buf: buffer for pathname
>> + * @n: buffer length (in) and pathname length (out)
>> + */
>> +static char *
>> +cr_fill_fname(struct path *path, struct path *root, char *buf, int *n)
>> +{
>> +	struct path tmp = *root;
>> +	char *fname;
>> +
>> +	BUG_ON(!buf);
>> +	fname = __d_path(path, &tmp, buf, *n);
>> +	if (!IS_ERR(fname))
>> +		*n = (buf + (*n) - fname);
>> +	/*
>> +	 * FIXME: if __d_path() changed these, it must have stepped out of
>> +	 * init's namespace. Since currently we require a unified namespace
>> +	 * within the container: simply fail.
>> +	 */
>> +	if (tmp.mnt != root->mnt || tmp.dentry != root->dentry)
>> +		fname = ERR_PTR(-EBADF);
> 
> ...
> 
>> +static int cr_ctx_checkpoint(struct cr_ctx *ctx, pid_t pid)
>> +{
>> +	ctx->root_pid = pid;
>> +
>> +	/*
>> +	 * assume checkpointer is in container's root vfs
>> +	 * FIXME: this works for now, but will change with real containers
>> +	 */
>> +	ctx->vfsroot = &current->fs->root;
>> +	path_get(ctx->vfsroot);
> 
> Hi Oren,
> 
> Is there really any good reason to use current->fs->root rather
> than ctx->root_task->fs->root here?

Oops, that's a leftover from before supporting external checkpoint.
Will fix.

> 
> The way I'm testing, the checkpointer is in fact in a different
> container, so the root passed into cr_fill_fname() is different
> from the container's root, so cr_fill_fname() always returns me
> -EBADF.
> 

Thanks,

Oren.
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