779457285a
The protocol for creating a new state in nfsd is to allocate the state leaving it largely uninitialised, add that state to the ->cl_stateids idr so as to reserve a state-id, then complete initialisation of the state and only set ->sc_type to non-zero once the state is fully initialised. If a state is found in the idr with ->sc_type == 0, it is ignored. The ->cl_lock lock is used to avoid races - it is held while checking sc_type during lookup, and held when a non-zero value is stored in ->sc_type. ... except... hash_delegation_locked() finalises the initialisation of a delegation state, but does NOT hold ->cl_lock. So this patch takes ->cl_lock at the appropriate time w.r.t other locks, and so ensures there are no races (which are extremely unlikely in any case). As ->fi_lock is often taken when ->cl_lock is held, we need to take ->cl_lock first of those two. Currently ->cl_lock and state_lock are never both taken at the same time. We need both for this patch so an arbitrary choice is needed concerning which to take first. As state_lock is more global, it might be more contended, so take it first. Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.