[Devel] Re: [PATCH 4/9] Introduce container dump function

[Andrey Mirkin]

On Wednesday 03 September 2008 18:23 Serge E. Hallyn wrote:
> Quoting Andrey Mirkin (major at openvz.org):
> > Actually right now we are going to dump only one process.
> > Function for dumping head of image file are added.
> >
> > Signed-off-by: Andrey Mirkin <major at openvz.org>
> > ---
> >  cpt/Makefile     |    2 +-
> >  cpt/checkpoint.c |   74
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++++ cpt/cpt.h        |
> >    3 ++
> >  cpt/sys.c        |    3 +-
> >  kernel/fork.c    |    2 +
> >  5 files changed, 82 insertions(+), 2 deletions(-)
> >  create mode 100644 cpt/checkpoint.c
> >
> > diff --git a/cpt/Makefile b/cpt/Makefile
> > index bfe75d5..173346b 100644
> > --- a/cpt/Makefile
> > +++ b/cpt/Makefile
> > @@ -2,4 +2,4 @@ obj-y += sys_core.o
> >
> >  obj-$(CONFIG_CHECKPOINT) += cptrst.o
> >
> > -cptrst-objs := sys.o
> > +cptrst-objs := sys.o checkpoint.o
> > diff --git a/cpt/checkpoint.c b/cpt/checkpoint.c
> > new file mode 100644
> > index 0000000..b4d9686
> > --- /dev/null
> > +++ b/cpt/checkpoint.c
> > @@ -0,0 +1,74 @@
> > +/*
> > + *  Copyright (C) 2008 Parallels, Inc.
> > + *
> > + *  Author: Andrey Mirkin <major at openvz.org>
> > + *
> > + *  This program is free software; you can redistribute it and/or
> > + *  modify it under the terms of the GNU General Public License as
> > + *  published by the Free Software Foundation, version 2 of the
> > + *  License.
> > + *
> > + */
> > +
> > +#include <linux/sched.h>
> > +#include <linux/fs.h>
> > +#include <linux/file.h>
> > +#include <linux/version.h>
> > +
> > +#include "cpt.h"
> > +
> > +static int cpt_write_head(struct cpt_context *ctx)
> > +{
> > +	struct cpt_head hdr;
> > +
> > +	memset(&hdr, 0, sizeof(hdr));
> > +	hdr.cpt_signature[0] = CPT_SIGNATURE0;
> > +	hdr.cpt_signature[1] = CPT_SIGNATURE1;
> > +	hdr.cpt_signature[2] = CPT_SIGNATURE2;
> > +	hdr.cpt_signature[3] = CPT_SIGNATURE3;
> > +	hdr.cpt_hdrlen = sizeof(hdr);
> > +	hdr.cpt_image_major = (LINUX_VERSION_CODE >> 16) & 0xff;
> > +	hdr.cpt_image_minor = (LINUX_VERSION_CODE >> 8) & 0xff;
> > +	hdr.cpt_image_sublevel = (LINUX_VERSION_CODE) & 0xff;
> > +	hdr.cpt_image_extra = 0;
> > +#if defined(CONFIG_X86_32)
> > +	hdr.cpt_arch = CPT_ARCH_I386;
> > +#else
> > +#error  Arch is not supported
> > +#endif
> > +	return ctx->write(&hdr, sizeof(hdr), ctx);
> > +}
> > +
> > +int dump_container(struct cpt_context *ctx)
> > +{
> > +	int err;
> > +	struct task_struct *root;
> > +
> > +	read_lock(&tasklist_lock);
> > +	root = find_task_by_vpid(ctx->pid);
> > +	if (root)
> > +		get_task_struct(root);
> > +	read_unlock(&tasklist_lock);
> > +
> > +	err = -ESRCH;
> > +	if (!root) {
> > +		eprintk("can not find root task\n");
> > +		return err;
> > +	}
> > +	ctx->nsproxy = root->nsproxy;
> > +	if (!ctx->nsproxy) {
> > +		eprintk("nsproxy is null\n");
> > +		goto out;
> > +	}
>
> The get_task_struct() above won't pin the tsk->nsproxy
> though, will it?  So should you be doing a
> 	rcu_read_lock();
> 	nsproxy = get_task_nsproxy(root);
> 	rcu_read_unlock();
> to make sure the nsproxy doesn't disappear out from under
> you?
>

You right here, will fix it in next version.

Thanks,
Andrey

>
> > +	err = cpt_write_head(ctx);
> > +
> > +	/* Dump task here */
> > +	if (!err)
> > +		err = -ENOSYS;
> > +
> > +out:
> > +	ctx->nsproxy = NULL;
> > +	put_task_struct(root);
> > +	return err;
> > +}
> > diff --git a/cpt/cpt.h b/cpt/cpt.h
> > index 607ac1b..b421a11 100644
> > --- a/cpt/cpt.h
> > +++ b/cpt/cpt.h
> > @@ -33,6 +33,7 @@ typedef struct cpt_context
> >  	int		refcount;
> >  	int		ctx_state;
> >  	struct semaphore main_sem;
> > +	struct nsproxy	*nsproxy;
> >
> >  	int		errno;
> >
> > @@ -54,3 +55,5 @@ extern int debug_level;
> >
> >  #define eprintk(a...) cpt_printk(1, "CPT ERR: " a)
> >  #define dprintk(a...) cpt_printk(1, "CPT DBG: " a)
> > +
> > +int dump_container(struct cpt_context *ctx);
> > diff --git a/cpt/sys.c b/cpt/sys.c
> > index 8334c4c..6801c22 100644
> > --- a/cpt/sys.c
> > +++ b/cpt/sys.c
> > @@ -109,9 +109,10 @@ static int checkpoint(pid_t pid, int fd, unsigned
> > long flags)
> >
> >  	ctx->file = file;
> >  	ctx->ctx_state = CPT_CTX_DUMPING;
> > +	ctx->pid = pid;
> >
> >  	/* checkpoint */
> > -	err = -ENOSYS;
> > +	err = dump_container(ctx);
> >
> >  	context_put(ctx);
> >
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 52b5037..f38b43d 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -77,6 +77,7 @@ int max_threads;		/* tunable limit on nr_threads */
> >  DEFINE_PER_CPU(unsigned long, process_counts) = 0;
> >
> >  __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
> > +EXPORT_SYMBOL(tasklist_lock);
> >
> >  int nr_processes(void)
> >  {
> > @@ -153,6 +154,7 @@ void __put_task_struct(struct task_struct *tsk)
> >  	if (!profile_handoff_task(tsk))
> >  		free_task(tsk);
> >  }
> > +EXPORT_SYMBOL(__put_task_struct);
> >
> >  /*
> >   * macro override instead of weak attribute alias, to workaround
> > --
> > 1.5.6
> >
> > _______________________________________________
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> > Containers at lists.linux-foundation.org
> > https://lists.linux-foundation.org/mailman/listinfo/containers
>
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