locks: fix tracking of inprogress lease breaks
We currently use a bit in fl_flags to record whether a lease is being broken, and set fl_type to the type (RDLCK or UNLCK) that it will eventually have. This means that once the lease break starts, we forget what the lease's type *used* to be. Breaking a read lease will then result in blocking read opens, even though there's no conflict--because the lease type is now F_UNLCK and we can no longer tell whether it was previously a read or write lease. So, instead keep fl_type as the original type (the type which we enforce), and keep track of whether we're unlocking or merely downgrading by replacing the single FL_INPROGRESS flag by FL_UNLOCK_PENDING and FL_DOWNGRADE_PENDING flags. To get this right we also need to track separate downgrade and break times, to handle the case where a write-leased file gets conflicting opens first for read, then later for write. (I first considered just eliminating the downgrade behavior completely--nfsv4 doesn't need it, and nobody as far as I can tell actually uses it currently--but Jeremy Allison tells me that Windows oplocks do behave this way, so Samba will probably use this some day.) Reviewed-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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