Inclusion of the cowloop driver into the mainline kernel turned out to be more difficult than anticipated. The 2.6.31 kernel has a totally revised block-driver request queue mechanism, which we were not aware of when we started the inclusion procedure and Greg Kroah-Hartman pulled cowloop v3.2 into his "staging driver" tree. However, this turned out to be Open Source Community functioning at its best, and we received lots of help and support from people who had found cowloop in that "staging driver" tree.

Apart from that, intensified stress testing revealed a rare race condition that had not been noticed before, and it took a lot of effort to pinpoint its cause. The many changes required by the new request handling, plus this race condition problem, plus all other changes proposed by Greg K-H and others, made us miss the deadline for the forthcoming new kernel release. Early October we have asked to retract the v3.2 driver.

However, development has continued and as we write this (late October) the driver is in good shape. We plan to re-submit it for inclusion again as version 3.3. All intended changes have been made, and all known problems have been fixed. The user-level utilities and the manpages have been revised substantially. We are currently going through a code review process and are doing more stress testing both on 32-bit kernels and on 64-bit kernels. It is expected that we can re-submit cowloop around mid-November. Until then, we will be happy to provide evaluation copies upon request.

• Patches added for kernels up to 2.27 (also tested on 2.28).
• No problems have been reported since the previous version. We have, however, received a handful of facility requests which have been incorporated. The most noticeable one is the possibility to configure the package to use a large number of cowfiles.
• An extensive stress test script, plus corresponding documentation, has been added. The documentation is also useable as a detailed step-by-step example for using the cowloop-mechanism.
• Minor changes and improvements have been applied to the documentation files.

• Driver bug fix to avoid 'scheduling while atomic'.
• Driver change to support many simultaneous cow devices in use.
• Addition of several driver management commands, based on new driver IOCTLs.
• Addition of a new command to the collection of support commands for the handling of cow files.

• Addition of cowmerge command to merge a rdofile permanently with its cowfile; the merged file can be used as new rdofile.
• Bug solution: Allow more than one open per cowdevice (needed for a.o. ReiserFS and XFS).

• Use multiple cowdevices in parallel (dynamically assigned).
• Support for read-only file and cowfile larger than 2 Gbytes.
• Minor bug solutions.

• Initial external release.

• Limited version of the cowloop driver (no active maintainance any more for version 1).