• David Howells's avatar
    kernfs, sysfs, cgroup, intel_rdt: Support fs_context · 23bf1b6b
    David Howells authored
    Make kernfs support superblock creation/mount/remount with fs_context.
    
    This requires that sysfs, cgroup and intel_rdt, which are built on kernfs,
    be made to support fs_context also.
    
    Notes:
    
     (1) A kernfs_fs_context struct is created to wrap fs_context and the
         kernfs mount parameters are moved in here (or are in fs_context).
    
     (2) kernfs_mount{,_ns}() are made into kernfs_get_tree().  The extra
         namespace tag parameter is passed in the context if desired
    
     (3) kernfs_free_fs_context() is provided as a destructor for the
         kernfs_fs_context struct, but for the moment it does nothing except
         get called in the right places.
    
     (4) sysfs doesn't wrap kernfs_fs_context since it has no parameters to
         pass, but possibly this should be done anyway in case someone wants to
         add a parameter in future.
    
     (5) A cgroup_fs_context struct is created to wrap kernfs_fs_context and
         the cgroup v1 and v2 mount parameters are all moved there.
    
     (6) cgroup1 parameter parsing error messages are now handled by invalf(),
         which allows userspace to collect them directly.
    
     (7) cgroup1 parameter cleanup is now done in the context destructor rather
         than in the mount/get_tree and remount functions.
    
    Weirdies:
    
     (*) cgroup_do_get_tree() calls cset_cgroup_from_root() with locks held,
         but then uses the resulting pointer after dropping the locks.  I'm
         told this is okay and needs commenting.
    
     (*) The cgroup refcount web.  This really needs documenting.
    
     (*) cgroup2 only has one root?
    
    Add a suggestion from Thomas Gleixner in which the RDT enablement code is
    placed into its own function.
    
    [folded a leak fix from Andrey Vagin]
    Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
    cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    cc: Tejun Heo <tj@kernel.org>
    cc: Li Zefan <lizefan@huawei.com>
    cc: Johannes Weiner <hannes@cmpxchg.org>
    cc: cgroups@vger.kernel.org
    cc: fenghua.yu@intel.com
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    23bf1b6b
mount.c 9.25 KB