Re: btrfs send/receive: if new inode ino is less than its new directory ino, incorrect path is sent

[Alexander Block <ablock84@googlemail.com>]

I have pushed a for-alex branch to github with a new approach for the
whole problem. Can you test this?

On Thu, Jul 26, 2012 at 4:07 PM, Alexander Block
<ablock84@googlemail.com> wrote:
> I'm currently working on another solution for the initial problem. I
> will create a for-alex branch for you to test later.
>
> On Thu, Jul 26, 2012 at 4:04 PM, Alex Lyakas
> <alex.bolshoy.btrfs@gmail.com> wrote:
>> Alexander,
>> (pls let me know when this gets annoying:).
>>
>> Parent:
>> /mnt/src/v2_snap0/
>> └── [    257]  file1
>>
>> Send:
>> /mnt/src/v2_snap1
>> └── [    259]  dir1
>>     └── [    258]  dir2
>>         └── [    257]  file1
>>
>> I encountered two problems:
>> 1) process_recorded_refs_if_needed() if needed does not call
>> process_recorded_refs() if both new_refs and deleted_refs() are empty.
>> But in this case, we need to get to finish_outoforder_dir() by dir2 to
>> move file1 under it (this is before dir1 is created).
>>
>> @@ -4199,8 +4227,25 @@ static int
>> process_recorded_refs_if_needed(struct send_ctx *sctx, int at_end)
>>         if (!at_end && sctx->cur_ino == sctx->cmp_key->objectid &&
>>             sctx->cmp_key->type <= BTRFS_INODE_REF_KEY)
>>                 goto out;
>> -       if (list_empty(&sctx->new_refs) && list_empty(&sctx->deleted_refs))
>> -               goto out;
>> +       if (list_empty(&sctx->new_refs) && list_empty(&sctx->deleted_refs) &&
>> +               /*
>> +                * If this is a new directory, still do the
>> finish_outoforder_dir() thing,
>> +                * even though it has no references recorded. This
>> means that the directory's
>> +                * parent has higher inode and was not created yet
>> (thus we should have
>> +                * sctx->cur_inode_first_ref_orphan flag set).
>> +                * Note that after a call to process_recorded_refs(),
>> new_refs and deleted_refs
>> +                * become empty, which prevents further calls to
>> process_recorded_refs(),
>> +                * but here we need something else to prevent it, so
>> look at send_progress too.
>> +                */
>> +               !(S_ISDIR(sctx->cur_inode_mode) && sctx->cur_inode_new &&
>> +                 sctx->cur_inode_first_ref_orphan &&
>> sctx->send_progress == sctx->cur_ino))
>> +               goto out;
>>
>>         ret = process_recorded_refs(sctx);
>>
>> Then I encountered another problem that finish_outoforder_dir() does
>> not check for itself the cur_inode_first_ref_orphan flag:
>> @@ -2736,7 +2754,17 @@ static int finish_outoforder_dir(struct
>> send_ctx *sctx, u64 dir, u64 dir_gen)
>>         }
>>         fctx.dir_ino = dir;
>>
>> -       ret = get_cur_path(sctx, dir, dir_gen, fctx.dir_path, 1/*do_print*/);
>> +       /*
>> +        * If the current directory itself has a parent, which was not
>> +        * created yet, we need to use gen_unique_name().
>> +        */
>> +       BUG_ON(sctx->cur_ino != dir || sctx->cur_inode_gen != dir_gen);
>> +       if (sctx->cur_inode_first_ref_orphan)
>> +               ret = gen_unique_name(sctx, dir, dir_gen, fctx.dir_path);
>> +       else
>> +               ret = get_cur_path(sctx, dir, dir_gen, fctx.dir_path);
>>
>> Finally, the send_truncate(), send_chmod(), send_chown(),send_utimes()
>> need the following check:
>>
>>         if (sctx->cur_ino == ino && sctx->cur_inode_first_ref_orphan) {
>>                 WARN_ON(sctx->cur_inode_gen != gen);
>>                 ret = gen_unique_name(sctx, ino, gen, p);
>>         } else {
>>                 ret = get_cur_path(sctx, ino, gen, p);
>>         }
>>
>> All of them except utimes() are used with cur_ino only, so for those
>> this check is redundant (and probably makes sense to drop ino/gen
>> parameters of them?).
>>
>> Thanks,
>> Alex.
>>
>>
>> On Thu, Jul 26, 2012 at 1:52 PM, Alex Lyakas
>> <alex.bolshoy.btrfs@gmail.com> wrote:
>>> Hi Alexander,
>>> I did some very initial testing, and there is still an issue.
>>> The logic of finish_outoforder_dir works as expected. But then problem
>>> is that later, when we process xattr/extents or finish the inode, the
>>> code still uses get_cur_path(), which brings an incorrect name.
>>>
>>> Consider the following simple scenario:
>>>
>>> Parent tree:
>>> /mnt/src/v2
>>> └── [    260]  file1
>>>
>>> Send tree:
>>> /mnt/src/v2
>>> └── [    262]  dir1
>>>     └── [    260]  file1
>>>
>>> So when file1 is being processed, it is first renamed, as expected:
>>>  C_RENAME: A_PATH=file1, A_PATH_TO=o260-511-0
>>> But then, when we finish it, we do:
>>> C_TRUNCATE: A_PATH=o262-517-0/file1, A_SIZE=16
>>>
>>> So in some functions like send_truncate(), send_write(), send_utimes()
>>> etc, we need:
>>>
>>> -       ret = get_cur_path(sctx, ino, gen, p, 0/*do_print*/);
>>> +       if (sctx->cur_inode_first_ref_orphan)
>>> +               ret = gen_unique_name(sctx, ino, gen, p);
>>> +       else
>>> +               ret = get_cur_path(sctx, ino, gen, p, 0/*do_print*/);
>>>         if (ret < 0)
>>>                 goto out;
>>>
>>> I will continue testing more complicated cases now.
>>>
>>> Thanks,
>>> Alex.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Jul 24, 2012 at 11:26 PM, Alexander Block
>>> <ablock84@googlemail.com> wrote:
>>>> On Wed, Jul 18, 2012 at 7:45 PM, Alex Lyakas
>>>> <alex.bolshoy.btrfs@gmail.com> wrote:
>>>>> Hi Alexander,
>>>>> I am testing different scenarios in order to better understand the
>>>>> non-trivial magic of
>>>>> get_cur_path()/will_overwrite_ref()/did_overwrite_ref()/did_overwrite_first_ref().
>>>>> I hit the following issue, when testing full-send:
>>>>>
>>>>> This is my source subvolume (inode numbers are written):
>>>>> tree -A  --inodes --noreport /mnt/src/tmp/
>>>>> /mnt/src/tmp/
>>>>> └── [    270]  dir2
>>>>>     └── [    268]  file1_nod
>>>>>
>>>>> As you see, the ino(file1_nod) < ino(dir2). It is very easy to
>>>>> achieve: first create the file, then the dir, and then move the file
>>>>> to dir.
>>>>>
>>>>> During send the following happens (I augmented the send code with many prints):
>>>>>
>>>>> file1_nod is sent first. Since its a new inode, it is sent as an
>>>>> orphan. When recording its reference, __record_new_ref() calls
>>>>> get_cur_path() for its parent (270). Then __get_cur_name_and_parent()
>>>>> is called on 270, which calls is_inode_existent(), which calls
>>>>> get_cur_inode_state(), and the state of the parent is "will_create".
>>>>> So __get_cur_name_and_parent() creates an orphan name for it, and
>>>>> finally the new reference for 268 is recorded as:
>>>>> o270-136-0/file1_nod:
>>>>>
>>>>> [changed_cb:4102] key(256 INODE_ITEM 0) : NEW
>>>>> [changed_cb:4102] key(256 INODE_REF 256) : NEW
>>>>> [changed_cb:4102] key(268 INODE_ITEM 0) : NEW
>>>>> [send_create_inode:2407] NEW ino(268,135) type=0100000, path=[o268-135-0]
>>>>> [changed_cb:4102] key(268 INODE_REF 270) : NEW
>>>>> [get_cur_inode_state:1475] (270,136): L(EX,136)
>>>>> R(NE,18446744072099047770) sp=268 ==> will_create
>>>>> [is_inode_existent:1498] (270,136): NOT existent
>>>>> [__get_cur_name_and_parent:1918] ino(270,136) not existent => unique
>>>>> name [o270-136-0]
>>>>> [get_cur_path:2051] ino(0,0) cur_path=[o270-136-0]
>>>>> [__record_new_ref:2911] record new ref [o270-136-0/file1_nod]
>>>>>
>>>>> Then process_recorded_refs() sees that 268 is still orphan, so it
>>>>> sends "rename" to its valid place, but the problem is that its parent
>>>>> dir was not sent yet (and its parent dir is also an orphan):
>>>>> [process_recorded_refs:2601] ino(268,135): start with refs
>>>>> [28118.347602] [process_recorded_refs:2651] ino(268,135): new=1,
>>>>> did_overwrite_first_ref=0, is_orphan=1, valid_path=[o268-135-0]
>>>>> [28118.347605] [process_recorded_refs:2701] ino(268,135): is orphan,
>>>>> move it: [o268-135-0]=>[o270-136-0/file1_nod]
>>>>> [28118.347610] [process_recorded_refs:2837] checking dir(270,136)
>>>>> [28118.347612] [process_recorded_refs:2869] ino(268,135) done with refs
>>>>>
>>>>> Now the parent dir is processed:
>>>>> [changed_cb:4102] key(270 INODE_ITEM 0) : NEW
>>>>> [send_create_inode:2407] NEW ino(270,136) type=040000, path=[o270-136-0]
>>>>> [changed_cb:4102] key(270 INODE_REF 256) : NEW
>>>>> [get_cur_path:2051] ino(256,133) cur_path=[]
>>>>> [__record_new_ref:2911] record new ref [dir2]
>>>>> [process_recorded_refs:2601] ino(270,136): start with refs
>>>>> [process_recorded_refs:2651] ino(270,136): new=1,
>>>>> did_overwrite_first_ref=0, is_orphan=1, valid_path=[o270-136-0]
>>>>> [process_recorded_refs:2701] ino(270,136): is orphan, move it:
>>>>> [o270-136-0]=>[dir2]
>>>>> [process_recorded_refs:2837] checking dir(256,133)
>>>>> [get_cur_inode_state:1475] (256,133): L(EX,133)
>>>>> R(NE,18446612135413283512) sp=270 ==> did_create
>>>>> [process_recorded_refs:2869] ino(270,136) done with refs
>>>>>
>>>>> Nothing special here, the parent is first sent as an orphan, and then
>>>>> renamed to its valid name, but it's too late.
>>>>>
>>>>> During receive:
>>>>> ERROR: rename o268-135-0 -> o270-136-0/file1_nod failed. No such file
>>>>> or directory
>>>>>
>>>>> I am not yet sure where is the proper place to fix this, I just wanted
>>>>> to report it first. Basically, I think that when sending any kind of
>>>>> A_PATH, it is needed to ensure that path components exist, either as
>>>>> orphan or real path (by sending them out-of-order if needed?). But I
>>>>> am not yet sure where is the core place that should ensure this.
>>>>>
>>>>> Thanks,
>>>>> Alex.
>>>>
>>>> I have pushed a fix for this case. Basically, the solution is to
>>>> postpone the processing of refs in not created dirs until the dir is
>>>> created. Big thanks for investigating this one.