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f52dc28322
We had an excessive number of layers between scoutfs and the dlm code in the kernel. We had dlmglue, the scoutfs locks, and task refs. Each layer had structs that track the lifetime of the layer below it. We were about to add another layer to hold on to locks just a bit longer so that we can avoid down conversion and transaction commit storms under contention. This collapses all those layers into simple state machine in lock.c that manages the mode of dlm locks on behalf of the file system. The users of the lock interface are mainly unchanged. We did change from a heavier trylock to a lighter nonblock lock attempt and have to change the single rare readpage use. Lock fields change so a few external users of those fields change. This not only removes a lot of code it also contains functional improvements. For example, it can now convert directly to CW locks with a single lock request instead of having to use two by first converting to NL. It introduces the concept of an unlock grace period. Locks won't be dropped on behalf of other nodes soon after being unlocked so that tasks have a chance to batch up work before the other node gets a chance. This can result in two orders of magnitude improvements in the time it takes to, say, change a set of xattrs on the same file population from two nodes concurrently. There are significant changes to trace points, counters, and debug files that follow the implementation changes. Signed-off-by: Zach Brown <zab@versity.com>