Jeff Layton has uploaded this change for review.
SAL: sticky grace periods
Some operations require a grace period, or that we not be in one.
Ganesha will generally check this prior to doing the operation, but
those checks are racy. We could end up flipping the state of grace after
checking but during or before the actual operation.
This is particularly a problem for clustered servers that may end up
going back into grace to satisfy the needs of another node, as they
could end up reporting that they are enforcing the grace period while
there are still ops in flight.
This patch adds some new grace period handling infrastructure to address
this. When ganesha needs to do an operation that requires a particular
state of grace, take a reference to that state to ensure that it can't
change until we are done.
If we go to start or lift the grace period, check first to see whether
there might be ops in flight. If there are, then set a flag indicating
that a change has been requested and don't do it.
If that flag is set, then we will no longer hand out grace period
references. Once the refcount goes to zero, we can allow the change to
occur and clear the flag so that new references can be acquired again.
We start by changing the usage of current_grace. It still contains when
the most recent grace period expires, but we don't use the value of 0 to
denote anything special now.
The other values are now tracked in a single uint32_t, which contains
two bitflags and a counter. By doing it this way, we can handle the most
common usage (getting/putting references) locklessly. Starting or
lifting the grace period still requires the grace_mutex however.
Change-Id: I7089cb468baaa64e98cc9c6220c009fc61c85840
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
M src/SAL/nfs4_recovery.c
M src/include/sal_functions.h
2 files changed, 151 insertions(+), 14 deletions(-)
git pull ssh://review.gerrithub.io:29418/ffilz/nfs-ganesha refs/changes/16/428016/1
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