[ANN] Squashfs 3.1 released

[Phillip Lougher <phillip@lougher.org.uk>]

Hi,

I'm pleased to announce Squashfs version 3.1.  Squashfs 3.1 has some
major improvements to the squashfs-tools, a couple of major bug fixes,
lots of small improvements/bug fixes, and new kernel patches.

Squashfs can be dowloaded from http://squashfs.sourceforge.net.
The list of changes  are:

1. Mksquashfs has been rewritten to be multi-threaded.  It has the
following improvements

1.1. Parallel compression.  By default as many compression and
     fragment compression threads are created as there are available
     processors.  This significantly speeds up performance on SMP
     systems.

1.2. File input and filesystem output is peformed in parallel on
     separate threads to maximise I/O performance.  Even on single
     processor systems this speeds up performance by at least 10%.

1.3. Appending has been significantly improved, and files within the
     filesystem being appended to are no longer scanned and
     checksummed.  This significantly improves append time for large
     filesystems.

1.4. File duplicate checking has been optimised, and split into two
     separate phases.  Only files which are considered possible
     duplicates after the first phase are checksummed and cached in
     memory.

1.5  The use of swap memory was found to significantly impact
     performance. The amount of memory used to cache files is now a
     command line option, by default this is 512 Mbytes.

2. Unsquashfs has the following improvements

2.1  Unsquashfs now allows you to specify the filename or the
     directory within the Squashfs filesystem that is to be
     extracted, rather than always extracting the entire filesystem.

2.2  A new -force option has been added which forces Unsquashfs to
     output to the destination directory even if files and directories
     already exist in the destination directory.  This allows you to
     update an already existing directory tree, or to Unsquashfs to
     a partially filled directory tree.  Without the -force option
     Unsquashfs will refuse to output.

3.  The following major bug fixes have been made

3.1   A fragment table rounding bug has been fixed in Mksquashfs.
      Previously if the number of fragments in the filesystem
      were a multiple of 512, Mksquashfs would generate an
      incorrect filesystem.

3.2   A rare SMP bug which occurred when simultaneously acccessing
      multiply mounted Squashfs filesystems has been fixed.

4. Miscellaneous improvements/bug fixes

4.1   Kernel code stack usage has been reduced.  This is to ensure
      Squashfs works with 4K stacks.

4.2   Readdir (Squashfs kernel code) has been fixed to always
      return 0, rather than the number of directories read.  Squashfs
      should now interact better with NFS.

4.3   Lseek bug in Mksquashfs when appending to larger than 4GB
      filesystems fixed.

4.4   Squashfs 2.x initrds can now been mounted.

4.5   Unsquashfs exit status fixed.

4.6   New patches for linux-2.6.18 and linux-2.4.33.

Comments, especially any performance results of the new parallelised
Mksquashfs are welcome.

Phillip

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