[CRIU] [PATCH v7 06/15] files: new "used" files list introduced

[Stanislav Kinsburskiy]

16.03.2016 11:18, Pavel Emelyanov пишет:
> On 03/14/2016 05:59 PM, Stanislav Kinsburskiy wrote:
>> 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 simple helper to find unused file descriptor.
>> Return "hint" if unused or last used descriptor plus one.
> I finally got what's bad with this patch -- the fact that you put collect_used_fd
> into all the ->collect_fd callbacks. This is dangerous as one more such callback
> and the whole logic gets broken.
>
> Plz, call the collect_used_fd in the core fd collecting routine, in the files.c's
> collect_fd() one.
>
>> +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) {
> You scan this list FULLY in find_unused_fd anyway, why keeping it sorted?

The reason is to find an unused fd, if hint_fd == -1 (or hint_fd != -1 
but it's busy)
If we have unsorted list like: { 1, 10, 2 9, 8} and searching for unused 
fd, how we will define one?

>> +		if (new_fle->fe->fd < fle->fe->fd)
>> +			break;
>> +	}
>> +
>> +	list_add_tail(&new_fle->used_list, &fle->used_list);
>> +}
>> +
>