[CRIU] [PATCH v2] filemap: collect mapped file fs type

[Stanislav Kinsburskiy]

29.07.2016 19:40, Andrew Vagin пишет:
> On Fri, Jul 29, 2016 at 11:33:43AM +0200, Stanislav Kinsburskiy wrote:
>>
>> 29.07.2016 04:37, Andrew Vagin пишет:
>>> On Thu, Jul 28, 2016 at 12:06:41PM +0300, Stanislav Kinsburskiy wrote:
>>>> This is essential to define whether this file is located on NFS (and thus has
>>>> to be "link-remapped") or not (see nfs_silly_renamed).
>>>>
>>>> v2:
>>>> Compilation issue fixed
>>>>
>>>> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
>>>> ---
>>>>    criu/cr-dump.c |    8 ++++++++
>>>>    1 file changed, 8 insertions(+)
>>>>
>>>> diff --git a/criu/cr-dump.c b/criu/cr-dump.c
>>>> index 06ff2d7..2288908 100644
>>>> --- a/criu/cr-dump.c
>>>> +++ b/criu/cr-dump.c
>>>> @@ -365,12 +365,20 @@ static int dump_filemap(struct vma_area *vma_area, int fd)
>>>>    	struct fd_parms p = FD_PARMS_INIT;
>>>>    	VmaEntry *vma = vma_area->e;
>>>>    	int ret = 0;
>>>> +	struct statfs fst;
>>>>    	u32 id;
>>>>    	BUG_ON(!vma_area->vmst);
>>>>    	p.stat = *vma_area->vmst;
>>>>    	p.mnt_id = vma_area->mnt_id;
>>>> +	if (fstatfs(fd, &fst)) {
>>>> +		pr_perror("Unable to statfs fd %d", fd);
>>>> +		return -1;
>>>> +	}
>>>> +
>>>> +	p.fs_type = fst.f_type;
>>> Can we get fs_type in handle_vma()? We get vmst and mnt_id there.
>> What do you mean?
>> Call fstatfs in handle_vma() or use of mnt_id?
>> And why we should do it in handle_vma?
> There is an optimization when a previous vma and the current one use the
> same file.
>
>
> if (vma_area->file_borrowed) {
> ...
>                  vma_area->vmst = prev->vmst;
>                  vma_area->mnt_id = prev->mnt_id;
> } else {
> ...
> }
>

Ok, but then:
1) FS type has to be placed on vma_area struct to be able to use this 
optimization pass it to dump_filemap.
2) File path is dumped for a vma regardless of this optimization.

So, I understand, that we can optimize away some statfs calls. But it 
looks somehow wrong to me.
If one vma has "file_borrowed" tag, then it probably means, that the 
same file shouldn't be dumped once more?
Is it correct?

>>>> +
>>>>    	/*
>>>>    	 * AUFS support to compensate for the kernel bug
>>>>    	 * exposing branch pathnames in map_files.
>>>>
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