VNPL 1.1 is slightly reworded to make it clear that proprietary software
interacting with Vitastor and providing some kind of service to end users isn't
a "Proxy Program" if it's not specially designed to be used with Vitastor.
For example, Windows OS running in a virtual machine stored in a Vitastor
cluster clearly isn't.
This is the new guaranteed unblocking method which replaces old trims
in init and rollback, and also fixes a possible stall when just several
writes in the beginning of the journal are flushed without triggering
a subsequent trim.
1) Update journal's used_start in memory only after updating journal superblock.
Doing the opposite is incorrect because part of the journal will be lost if writers
overwrite its old beginning.
2) Sync journal device after updating the superblock.
3) Do not trim in rollback and init because trimming there would also require
updating the superblock. And the only reason to trim in both those places was
to unblock writers. And a guaranteed unblocking method will follow in the next
commit :)
Instead of only removing versions with oid == X and version > Y it was
also removing the previous version in list (with the previous oid or
with version == Y)
Notably:
- fix the `delete op` inside lambda callback crash (it frees the lambda itself
which results in use-after-free with g++)
- fix stop_client() reenterability
- fix a bug in the blockstore layer which resulted in always returning version=0
for zero-length reads
- change error codes for blockstore_stabilize
Vitaliy Filippov