+This patch is no longer needed for Lustre. It is only included
+for testing and ease of using the same kernel with older Lustre
+versions. This testing functionality was replaced in Linux 3.0
+by the dm-flakey driver.
+
+This functionality is mainly used during testing, in order to
+simulate a server crash for ldiskfs by discarding all of the
+writes to the filesystem. For recovery testing we could simulate
+this by using a special loopback or DM device that also discards
+writes to the device.
+
+This functionality is also used by target "failback" in order
+to speed up service shutdown and takeover by the other node
+during controlled operation. However, it would also be possible
+to do this by simply allowing all of the in-flight requests to
+complete and then waiting for the service to stop. This will
+also be needed by the DMU-OSD, because discarding of writes on
+a DMU-based target is not safe as it could trigger a storage
+failure if the data is ever read from disk again and the
+checksum does not match that expected by the block pointer.
+
git://git.whamcloud.com / fs / lustre-release.git / blobdiff