[CRIU] [PATCH 13/14] restore: restore pocesses which share one fdtable (v4)

[Pavel Emelyanov]

On 01/11/2013 01:22 PM, Andrey Vagin wrote:
> Currenly crtools supports a case when a child shared a fd table
> with parent.
> 
> Here is only two interesting things.
> * Service descriptors should be cloned for each process
>   who shared one fd table.
> * One task should restore files and other tasks should sleep in this
> * time.
> 
> v2: * allocate fdt_lock from shared memory
>     * don't wait a child, if it doesn't share fdtable
> v3: * don't move ids on the pstree image
> v4: * save ids in a separate image
>     * save fdinfo per id instead of pid
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  cr-dump.c         | 12 +++++++-----
>  cr-restore.c      | 17 ++++++++++++++---
>  files.c           | 28 ++++++++++++++++++++++------
>  include/crtools.h |  1 +
>  pstree.c          |  1 +
>  5 files changed, 45 insertions(+), 14 deletions(-)
> 
> diff --git a/cr-dump.c b/cr-dump.c
> index fb81bc4..7384a56 100644
> --- a/cr-dump.c
> +++ b/cr-dump.c
> @@ -692,7 +692,7 @@ static int dump_task_kobj_ids(struct pstree_item *item)
>  
>  	new = 0;
>  	ids->files_id = kid_generate_gen(&files_tree, &elem, &new);
> -	if (!ids->files_id || !new) {
> +	if (!ids->files_id || (!new && !shared_fdtable(item))) {
>  		pr_err("Can't make FILES id for %d\n", pid);
>  		return -1;
>  	}
> @@ -1434,10 +1434,12 @@ static int dump_one_task(struct pstree_item *item)
>  		goto err_cure;
>  	}
>  
> -	ret = dump_task_files_seized(parasite_ctl, item, dfds);
> -	if (ret) {
> -		pr_err("Dump files (pid: %d) failed with %d\n", pid, ret);
> -		goto err_cure;
> +	if (!shared_fdtable(item)) {
> +		ret = dump_task_files_seized(parasite_ctl, item, dfds);
> +		if (ret) {
> +			pr_err("Dump files (pid: %d) failed with %d\n", pid, ret);
> +			goto err_cure;
> +		}
>  	}
>  
>  	ret = parasite_dump_pages_seized(parasite_ctl, &vma_area_list, cr_fdset);
> diff --git a/cr-restore.c b/cr-restore.c
> index ccc404d..9b69eff 100644
> --- a/cr-restore.c
> +++ b/cr-restore.c
> @@ -808,6 +808,9 @@ static inline int fork_with_pid(struct pstree_item *item, unsigned long ns_clone
>  	ca.item = item;
>  	ca.clone_flags = ns_clone_flags;
>  
> +	if (shared_fdtable(item))
> +		ca.clone_flags |= CLONE_FILES;
> +
>  	if (!(ca.clone_flags & CLONE_NEWPID)) {
>  		char buf[32];
>  
> @@ -995,11 +998,19 @@ static int restore_task_with_children(void *_arg)
>  	int ret;
>  	sigset_t blockmask;
>  
> -	close_safe(&ca->fd);
> -	close_old_fds(current);
> -
>  	current = ca->item;

Huh? Was current uninitialized before this patch?

>  
> +	if ( !(ca->clone_flags & CLONE_FILES)) {
> +		close_safe(&ca->fd);
> +		close_old_fds(current);
> +	}
> +
> +	if (current->state != TASK_HELPER) {
> +		ret = clone_service_fd(current->rst->service_fd_id);
> +		if (ret)
> +			exit(1);
> +	}
> +
>  	pid = getpid();
>  	if (current->pid.virt != pid) {
>  		pr_err("Pid %d do not match expected %d\n", pid, current->pid.virt);
> diff --git a/files.c b/files.c
> index 2a22c3a..681ff47 100644
> --- a/files.c
> +++ b/files.c
> @@ -541,15 +541,29 @@ int close_old_fds(struct pstree_item *me)
>  
>  int prepare_fds(struct pstree_item *me)
>  {
> -	u32 ret;
> +	u32 ret = 0;
>  	int state;
>  
> -	ret = close_old_fds(me);
> -	if (ret)
> -		goto err;
> -
>  	pr_info("Opening fdinfo-s\n");
>  
> +	if (me->rst->fdt) {
> +		struct fdt *fdt = me->rst->fdt;
> +
> +		/*
> +		 * Wait all tasks, who share a current fd table.
> +		 * We should be sure, that nobody use any file
> +		 * descriptor while fdtable is being restored.
> +		 */
> +		futex_inc_and_wake(&fdt->fdt_lock);
> +		futex_wait_while_lt(&fdt->fdt_lock, fdt->nr);
> +
> +		if (fdt->pid != me->pid.virt) {
> +			pr_info("File descriptor talbe is shared with %d\n", fdt->pid);
> +			futex_wait_until(&fdt->fdt_lock, fdt->nr + 1);
> +			goto out;
> +		}
> +	}
> +
>  	for (state = 0; state < ARRAY_SIZE(states); state++) {
>  		ret = open_fdinfos(me->pid.virt, &me->rst->fds, state);
>  		if (ret)
> @@ -573,7 +587,9 @@ int prepare_fds(struct pstree_item *me)
>  			break;
>  	}
>  
> -err:
> +	if (me->rst->fdt)
> +		futex_inc_and_wake(&me->rst->fdt->fdt_lock);
> +out:
>  	tty_fini_fds();
>  	return ret;
>  }
> diff --git a/include/crtools.h b/include/crtools.h
> index 00c917d..7a7f101 100644
> --- a/include/crtools.h
> +++ b/include/crtools.h
> @@ -244,6 +244,7 @@ struct rst_info {
>  	void			*premmapped_addr;
>  	unsigned long		premmapped_len;
>  
> +	int service_fd_id;

Alignment.

>  	struct fdt		*fdt;
>  };
>  
> diff --git a/pstree.c b/pstree.c
> index 85371d7..a9987f9 100644
> --- a/pstree.c
> +++ b/pstree.c
> @@ -463,6 +463,7 @@ static int prepare_pstree_ids(void)
>  			fdt = parent->rst->fdt;
>  
>  		item->rst->fdt = fdt;
> +		item->rst->service_fd_id = fdt->nr;
>  		fdt->nr++;
>  		if (fdt->pid > item->pid.virt)
>  			fdt->pid = item->pid.virt;
>