Welcome to the Reiser4 Wiki, the Wiki for users and developers of the ReiserFS and Reiser4 filesystems.

For now, most of the documentation is just a snapshot of the old Namesys site (archive.org, 2007-09-29).

There was also a Reiser4 Wiki (archive.org, 2007-07-06) once on pub.namesys.com.

TODO

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When [[Namesys]] was still in place, there was a [http://pub.namesys.com/Reiser4/ToDo TODO list] to work on to get [[Reiser4]] into mainline. This URL is no more, but back in 08/2008, Andrew and Edward put together an [http://marc.info/?l=reiserfs-devel&m=121789281206672&w=2 updated Reiser4 TODO list]:
 
When [[Namesys]] was still in place, there was a [http://pub.namesys.com/Reiser4/ToDo TODO list] to work on to get [[Reiser4]] into mainline. This URL is no more, but back in 08/2008, Andrew and Edward put together an [http://marc.info/?l=reiserfs-devel&m=121789281206672&w=2 updated Reiser4 TODO list]:
  
<pre>
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* [[TODO/2007-11-25|original TODO list from 2007-11-25]]
List:      reiserfs-devel
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* [[TODO/2008-08-04|updated TODO list from 2008-08-04]]
Subject:    Todo for inclusion (updated 05 Aug 2008)
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From:      Edward Shishkin <edward.shishkin () gmail ! com>
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Date:      2008-08-04 23:35:32
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Message-ID: 48979244.3040903 () gmail ! com
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[Download message RAW]
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Todo for inclusion (updated 05 Aug 2008)
 
 
 
The updated todo-list initially composed by Akpm is attached.
 
It makes sense to try to address the following items
 
(complexity is increased):
 
 
#10,11: Cleanups.
 
 
#3 There is a pending patch to review/merge:
 
http://marc.info/?l=reiserfs-devel&m=119316601418489&w=2
 
 
#9: I don't see any leaked jref there. Perhaps we need to rewrite this
 
portion of code to make it more clear.
 
 
#14 needs to be addressed.
 
 
["todo_for_inclusion_cached" (text/plain)]
 
 
Tasks are needed to done for getting reiser4 code into the kernel as found by AKPM
 
in 2.6.18-rc2-mm1 (# means that an issue is done)
 
 
1. running igrab() in the writepage() path is really going to hammer inode_lock.
 
  Something else will need to be done here.
 
 
2. The preferred way of solving the above would be to mark the page as
 
  PageWriteback() with set_page_writeback() prior to unlocking it. That'll pin
 
  the page and the inode. It does require that the page actually get written later on.
 
  If we cannot do that then more thought is needed.
 
 
3. If poss, use wake_up_process() rather than wake_up(). That'll save some locking.
 
 
4. Running iput() in entd() is a bit surprising. iirc there are various ways in which
 
  this can recur into the filesystem, perform I/O, etc. I guess it works.. But again,
 
  it will hammer inode_lock.
 
 
5. the writeout logic in entd_flush() is interesting (as in "holy cow"). It's very
 
  central and really needs some good comments describing what's going on in there -
 
  what problems are being solved, which decisions were taken and why, etc. The big
 
  comment in page_cache.c is useful. Please maintain it well. Boy, it has some old
 
  stuff in it.
 
 
6. reiser4_wait_page_writeback() needs commenting.
 
 
7. reading the comment in txnmgr.c regarding MAP_SHARED pages: a number of things
 
  have changed since then. We have page-becoming-writeable notifications and probably
 
  soon we'll always take a pagefault when a MAP_SHARED page transitions from pte-clean
 
  to pte-dirty (although I wouldn't recommend that a filesystem rely upon the latter
 
  for a while yet).
 
 
8. page_cache.c: yes, mpage_end_io_write() and mpage_end_io_read() are pretty generic
 
  - we might as well export them.
 
 
9. truncate_jnodes_range() looks wrong to me. When we populate gang[], there can be any
 
  number of NULL entries placed in it. But the loop which iterates across the
 
  now-populated gang[] will bale out when it its the _first_ NULL entry. Any following
 
  entries will have a leaked jref() against them.
 
 
10. Waaaaaaaaaaaaaaay too many typedefs.
 
 
11. There are many coding-style nits. One I will mention is very large number of unneeded braces:
 
          * if (foo) {
 
                o bar();
 
            }
 
      it'd be nice to fix these up sometime. Note: Easy to find and repair with checkpatch.pl
 
script found at http://www.kernel.org/pub/linux/kernel/people/apw/checkpatch/
 
 
12. General comment: the lack of support for extended attributes, access control lists and
 
    direct-io is a big problem and it's getting bigger. I don't see how a vendor could
 
    support reiser4 without these features and permanent lack of vendor support will hurt.
 
    What's the plan here?
 
 
13. (from CH) Another issue is the lack of support for blocksize < pagesize. This prevents it
 
    from being used across architectures. Even worse when I tried the last time it didn't allow
 
    me to create a 64k blocksize filesystem that I could actually test on ppc64.  \
 
 
14. set_page_dirty_internal() pokes around in VFS internals. Use set_page_dirty_no_buffers()
 
    or create a new library function in mm/page-writeback.c. In particular, it gets the
 
    radix-tree dirty tagging out of sync.
 
 
15. #wbq.sem should be using a completion for the "wait until entd finishes", not a semaphore.
 
    Because there's a teeny theoretical race when using semaphores this way which completions
 
    were designed to avoid. (The waker can still be playing with the semaphore when it has
 
    gone out of scope on the wakee's stack).
 
 
16. #write_page_by_ent(): the "spin until entd thread" thing is gross. This function is really
 
    lock-intensive.
 
 
17. #entd_flush(): bug:
 
      rq->wbc->range_start = rq->page->index << PAGE_CACHE_SHIFT;
 
    this can overflow on 32-bit. Need to cast rq->page->index to loff_t.
 
 
18. #writeout() is a poor name for a global function. Even things like "txn_restart" are a bit
 
    generic-sounding. Low-risk, but the kernel's getting bigger... If it were mine, I'd prefix
 
    all these symbols with "r4_". prepare_to_sleep(), page_io(), drop_page(), statfs_type(),
 
    pre_commit_hook(), etc, etc, etc, etc. Much namespace pollution.
 
 
19. #invalidate_list() is a poorly-chosen global identifier. We already have an invalidate_list()
 
    in fs/inode.c, too. Please audit all of reiser4's global identifiers (use nm *.o) for
 
    suitable naming choices.
 
 
20. #semaphores are deprecated. Please switch to mutexes and/or completions where appropriate
 
    and possible.
 
 
21. #drop_page() is a worry. Why _does_ reiser4 need to remove pages from pagecache? That
 
    isn't a filesystem function. drop_page() appears to leave the no-longer-present page tagged
 
    as dirty in the radix-tree.
 
 
22. #reiser4_invalidate_pages() is a mix of reiser4 things and of things-which-the-vfs-is-supposed-to-do.
 
    It is uncommented and I am unable to work out why it was necessary to do this, and hence what we
 
    can do about it.
 
 
23. #reiser4_readpages() shouldn't need to clean up the remaining pages on *pages. read_cache_pages()
 
    does that now.
 
 
24. #<wonders what formatted and unformatted nodes are> A brief glossary might help.
 
 
25. #REISER4_ERROR_CODE_BASE actually overlaps real errnos (see include/linux/errno.h). Suggest that
 
    it be changed to 1000000 or something.
 
 
26. #blocknr_set_add() modifies a list_head without any apparent locking. Certainly without any
 
    _documented_ locking... Ditto blocknr_set_destroy(). I'm sure there's locking, but it's harder than
 
    it should be to work out what it is. Given that proper locking is in place, the filesystem seems to
 
    use list_*_careful() a lot more than is necessary?
 
 
27. #It would be clearer to remove `struct blocknr_set' and just use list_head.
 
 
Last update: 02/06/2007
 
Reiser4/ToDo (last edited 2007-11-25 21:57:14 by M9132)
 
</pre>
 
  
 
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Revision as of 21:28, 26 June 2009

When Namesys was still in place, there was a TODO list to work on to get Reiser4 into mainline. This URL is no more, but back in 08/2008, Andrew and Edward put together an updated Reiser4 TODO list:



Reiser4 inclusion seems to be in sight, rumor has it that another attempt will be made later this year.

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