[CRIU] [PATCH v8 06/15] files: new "used" files list introduced

[Kirill Tkhai]

В Чт, 26/05/2016 в 15:21 +0200, Stanislav Kinsburskiy пишет:
> 
> 26.05.2016 15:20, Kirill Tkhai пишет:
> > 
> > В Ср, 16/03/2016 в 16:17 +0300, Stanislav Kinsburskiy пишет:
> > > 
> > > This list contains all per-process used file fdinfo's, sorted by
> > > fd
> > > number.
> > > Will be used to safely create new artificial file descriptors and
> > > also allow
> > > to recreate temporary descriptors with original number, if
> > > possible,
> > > like
> > > AutoFS tries to preserve original pipe write end descriptor, when
> > > it
> > > was
> > > closed.
> > > This patch also adds a couple of simple helpers to find unused
> > > file
> > > descriptor:
> > > 1) fd_is_used() does exactly what it is named
> > > 2) find_unused_fd() returns "hint_fd" if unused or last used
> > > descriptor plus
> > > one.
> > > 
> > > Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
> > > ---
> > >   criu/files.c            |    3 +++
> > >   criu/include/files.h    |   33
> > > +++++++++++++++++++++++++++++++++
> > >   criu/include/rst_info.h |    1 +
> > >   3 files changed, 37 insertions(+)
> > > 
> > > diff --git a/criu/files.c b/criu/files.c
> > > index 8a7d85f..40bb13a 100644
> > > --- a/criu/files.c
> > > +++ b/criu/files.c
> > > @@ -646,6 +646,8 @@ static int collect_fd(int pid, FdinfoEntry
> > > *e,
> > > struct rst_info *rst_info)
> > >   	else
> > >   		collect_gen_fd(new_le, rst_info);
> > >   
> > > +	collect_used_fd(new_le, rst_info);
> > > +
> > >   	list_add_tail(&new_le->desc_list, &le->desc_list);
> > >   	new_le->desc = fdesc;
> > >   
> > > @@ -686,6 +688,7 @@ int prepare_fd_pid(struct pstree_item *item)
> > >   	pid_t pid = item->pid.virt;
> > >   	struct rst_info *rst_info = rsti(item);
> > >   
> > > +	INIT_LIST_HEAD(&rst_info->used);
> > >   	INIT_LIST_HEAD(&rst_info->fds);
> > >   	INIT_LIST_HEAD(&rst_info->eventpoll);
> > >   	INIT_LIST_HEAD(&rst_info->tty_slaves);
> > > diff --git a/criu/include/files.h b/criu/include/files.h
> > > index 5db6ab1..d38dbfd 100644
> > > --- a/criu/include/files.h
> > > +++ b/criu/include/files.h
> > > @@ -67,6 +67,7 @@ struct fdinfo_list_entry {
> > >   	struct list_head	desc_list;	/* To chain
> > > on  @fd_info_head */
> > >   	struct file_desc	*desc;		/*
> > > Associated
> > > file descriptor */
> > >   	struct list_head	ps_list;	/* To
> > > chain  per-
> > > task files */
> > > +	struct list_head	used_list;	/* To chain
> > > per-
> > > task used fds */
> > >   	int			pid;
> > >   	futex_t			real_pid;
> > >   	FdinfoEntry		*fe;
> > > @@ -108,11 +109,43 @@ struct file_desc_ops {
> > >   	char *			(*name)(struct file_desc
> > > *,
> > > char *b, size_t s);
> > >   };
> > >   
> > > +static inline void collect_used_fd(struct fdinfo_list_entry
> > > *new_fle, struct rst_info *ri)
> > > +{
> > > +	struct fdinfo_list_entry *fle;
> > > +
> > > +	list_for_each_entry(fle, &ri->used, used_list) {
> > > +		if (new_fle->fe->fd < fle->fe->fd)
> > > +			break;
> > > +	}
> > > +
> > > +	list_add_tail(&new_fle->used_list, &fle->used_list);
> > > +}
> > > +
> > >   static inline void collect_gen_fd(struct fdinfo_list_entry
> > > *fle,
> > > struct rst_info *ri)
> > >   {
> > >   	list_add_tail(&fle->ps_list, &ri->fds);
> > >   }
> > >   
> > > +static inline bool fd_is_used(struct list_head *head, int fd)
> > > +{
> > > +	struct fdinfo_list_entry *fle;
> > > +
> > > +	list_for_each_entry(fle, head, used_list) {
> > > +		if (fle->fe->fd == fd)
> > > +			return true;
> > > +	}
> > > +
> > > +	return false;
> > > +}
> > > +
> > > +static inline unsigned int find_unused_fd(struct list_head
> > > *head,
> > > int hint_fd)
> > > +{
> > > +	if ((hint_fd >= 0) && (!fd_is_used(head, hint_fd)))
> > > +		return hint_fd;
> > > +	/* Return last used fd +1 */
> > > +	return list_entry(head->prev, typeof(struct
> > > fdinfo_list_entry), used_list)->fe->fd + 1;
> > What is guarantee that we have a space between the last fd and
> > INT/UINT_MAX?
> > 
> Frankly speaking, there is no garantee.

Ok. Is this behavior expected for autofs (because of true hint_fd etc)?
I try to understand if it's need just for me or it's common question.

> > 
> > > 
> > > +}
> > > +
> > >   struct file_desc {
> > >   	u32			id;		/* File
> > > id,
> > > unique */
> > >   	struct hlist_node	hash;		/*
> > > Descriptor
> > > hashing and lookup */
> > > diff --git a/criu/include/rst_info.h b/criu/include/rst_info.h
> > > index b6d378e..562e2f0 100644
> > > --- a/criu/include/rst_info.h
> > > +++ b/criu/include/rst_info.h
> > > @@ -27,6 +27,7 @@ struct fdt {
> > >   struct _MmEntry;
> > >   
> > >   struct rst_info {
> > > +	struct list_head	used;
> > >   	struct list_head	fds;
> > >   	struct list_head	eventpoll;
> > >   	struct list_head	tty_slaves;
> > > 
> > > _______________________________________________
> > > CRIU mailing list
> > > CRIU at openvz.org
> > > https://lists.openvz.org/mailman/listinfo/criu