Name
  Suleiman Souhlal

Email
  ssouhlal@vt.edu

Project Title
  UFS Journaling

Synopsis
  Add metadata journaling to the UFS filesystem. This will ensure that
the filesystem metadata can be easily made consistent after an
improper shutdown.

Benefits To The Community
  Currently, in case of an improper shutdown, the hard drives have to be
fsck'ed. While softupdates alleviate the problem, by permitting the
disk to be used while fsck is running in the background, it is still a
long process, and uses significant system resources. Adding metadata
journaling and journal replay would permit to skip the fsck phase
completely, by replaying the transactions that were not completely
committed to disk when the crash happened.

Deliverables
  Implement metadata journaling for the UFS filesystem.

Project Details
  In order to implement UFS journaling, we will start by examining the
work done by Scott Long (scottl@FreeBSD.org), which resides in the
FreeBSD Perforce repository. After that, the first step will be to
modify the vm/buffer cache so that buffers will not get flushed to
disk when pinned. This will enable us to first write metadata
buffers to the journal, and only once the disk reports that they
have been committed to the journal can they be written to their
actual location on disk.
  Once that is done, we will be able to implement the various journal
operations: 
    - Initialize the journal (which Scott has already implemented)
    - Destroy the journal, flushing the journal when umounting the filesystem
    - Start a transaction, assigning a journal handle for future
      operations
    - End a transaction, starting to write the whole transaction to
      disk
    - Write blocks, adding them to our transaction.
  Finally, we will identify the parts of the UFS filesystem that modify
metadata, and we will change them so that they use our journal
operations. This will probably be the most involved part, as the UFS
code is fairly complex.

Project Schedule
   I expect that at least two months will be needed to complete this project.

Bio
  I am a Computer Science and Mathematics undergraduate student at
Virginia Tech, expecting to graduate in July 2005. I am also a FreeBSD
committer, officially working on the PowerPC port, but lately, I have
been working on other areas of the kernel as well, including VFS and
local filesystems.