[CRIU] [PATCH] link_remap: do not create excessive links for a single file

[Stanislav Kinsburskiy]

13.07.2016 16:30, Pavel Emelyanov пишет:
> On 07/13/2016 04:10 PM, Stanislav Kinsburskiy wrote:
>>
>> 13.07.2016 14:48, Pavel Emelyanov пишет:
>>> On 06/30/2016 08:11 PM, Stanislav Kinsburskiy wrote:
>>>> Currently criu always creates link for each file, considered as "silly-renamed".
>>>> Even in those cases, when file is opened multiple times, it creates one new
>>>> link for each occurrence.
>>>> On restore only one link file is used for all the file descriptors, sharing
>>>> this path. And only this link is removed.
>>> Would you cook a zdtm test showing it?
>> Sorry, I don't understand. Showing what exactly?
>> I caught by using zdtm tests. Test "static/unlink_mmap00" should expose it.
>> Two links created, only one used and unlinked. Another one stays on the
>> disk.
> And test passes :) Then modify it (or it's cleanup hook) to catch this error.

Checking for no "link_remap*" files left suits your purpose?

>>>> The rest of the links are forgotten and abandoned on file system.
>>>> This patch fixed this mess by creating the link only iff it's unique. Or
>>>> skipping this job otherwise.
>>>>
>>>> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
>>>> ---
>>>>    criu/files-reg.c |   50 ++++++++++++++++++++++++++++++++++++++++++++------
>>>>    1 file changed, 44 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/criu/files-reg.c b/criu/files-reg.c
>>>> index fd36ae9..b1ad271 100644
>>>> --- a/criu/files-reg.c
>>>> +++ b/criu/files-reg.c
>>>> @@ -70,9 +70,11 @@ struct link_remap_rlb {
>>>>    	struct list_head	list;
>>>>    	struct ns_id		*mnt_ns;
>>>>    	char			*path;
>>>> +	char			*orig;
>>>> +	u32			id;
>>>>    };
>>>>    
>>>> -static int note_link_remap(char *path, struct ns_id *nsid)
>>>> +static int note_link_remap(char *path, char *orig, struct ns_id *nsid, u32 id)
>>>>    {
>>>>    	struct link_remap_rlb *rlb;
>>>>    
>>>> @@ -84,11 +86,18 @@ static int note_link_remap(char *path, struct ns_id *nsid)
>>>>    	if (!rlb->path)
>>>>    		goto err2;
>>>>    
>>>> +	rlb->orig = strdup(orig);
>>>> +	if (!rlb->orig)
>>>> +		goto err3;
>>>> +
>>>>    	rlb->mnt_ns = nsid;
>>>> +	rlb->id = id;
>>>>    	list_add(&rlb->list, &remaps);
>>>>    
>>>>    	return 0;
>>>>    
>>>> +err3:
>>>> +	xfree(rlb->path);
>>>>    err2:
>>>>    	xfree(rlb);
>>>>    err:
>>>> @@ -96,6 +105,22 @@ err:
>>>>    	return -1;
>>>>    }
>>>>    
>>>> +static int find_link_remap(char *path, struct ns_id *nsid, u32 *id)
>>>> +{
>>>> +	struct link_remap_rlb *rlb;
>>>> +
>>>> +	list_for_each_entry(rlb, &remaps, list) {
>>>> +		if (rlb->mnt_ns != nsid)
>>>> +			continue;
>>>> +		if (strcmp(rlb->orig, path))
>>>> +			continue;
>>>> +
>>>> +		*id = rlb->id;
>>>> +		return 0;
>>>> +	}
>>>> +	return -ENOENT;
>>>> +}
>>>> +
>>>>    /* Trim "a/b/c/d" to "a/b/d" */
>>>>    static int trim_last_parent(char *path)
>>>>    {
>>>> @@ -725,6 +750,7 @@ static void __rollback_link_remaps(bool do_unlink)
>>>>    		}
>>>>    
>>>>    		list_del(&rlb->list);
>>>> +		xfree(rlb->orig);
>>>>    		xfree(rlb->path);
>>>>    		xfree(rlb);
>>>>    	}
>>>> @@ -781,28 +807,40 @@ static int create_link_remap(char *path, int len, int lfd,
>>>>    		return -1;
>>>>    	}
>>>>    
>>>> -	if (note_link_remap(link_name, nsid))
>>>> +	if (note_link_remap(link_name, path, nsid, *idp))
>>>>    		return -1;
>>>>    
>>>>    	return pb_write_one(img_from_set(glob_imgset, CR_FD_REG_FILES), &rfe, PB_REG_FILE);
>>>>    }
>>>>    
>>>> -static int dump_linked_remap(char *path, int len, const struct stat *ost,
>>>> -				int lfd, u32 id, struct ns_id *nsid)
>>>> +static int dump_linked_remap_type(char *path, int len, int lfd, u32 id, struct ns_id *nsid, RemapType remap_type, bool unique)
>>>>    {
>>>>    	u32 lid;
>>>>    	RemapFilePathEntry rpe = REMAP_FILE_PATH_ENTRY__INIT;
>>>>    
>>>> -	if (create_link_remap(path, len, lfd, &lid, nsid))
>>>> -		return -1;
>>>> +	if (!find_link_remap(path, nsid, &lid)) {
>>>> +		pr_debug("Link remap for %s already exists with id %x\n",
>>>> +				path, lid);
>>>> +		if (unique)
>>>> +			return 0;
>>>> +	} else if (create_link_remap(path, len, lfd, &lid, nsid))
>>>> +			return -1;
>>>>    
>>>>    	rpe.orig_id = id;
>>>>    	rpe.remap_id = lid;
>>>> +	rpe.has_remap_type = true;
>>>> +	rpe.remap_type = remap_type;
>>>>    
>>>>    	return pb_write_one(img_from_set(glob_imgset, CR_FD_REMAP_FPATH),
>>>>    			&rpe, PB_REMAP_FPATH);
>>>>    }
>>>>    
>>>> +static int dump_linked_remap(char *path, int len, const struct stat *ost,
>>>> +				int lfd, u32 id, struct ns_id *nsid)
>>>> +{
>>>> +	return dump_linked_remap_type(path, len, lfd, id, nsid, REMAP_TYPE__LINKED, false);
>>>> +}
>>>> +
>>>>    static pid_t *dead_pids;
>>>>    static int n_dead_pids;
>>>>    
>>>>
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>>>> .
>>>>
>> .
>>