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kernfs_node->attr.open is an RCU pointer to kernfs_open_node. However, RCU dereference is currently only used in kernfs_notify(). Everywhere else, either we're holding the lock which protects it or know that the kernfs_open_node is pinned becaused we have a pointer to a kernfs_open_file which is hanging off of it. kernfs_deref_open_node() is used for the latter case - accessing kernfs_open_node from kernfs_open_file. The lifetime and visibility rules are simple and clear here. To someone who can access a kernfs_open_file, its kernfs_open_node is pinned and visible through of->kn->attr.open. Replace kernfs_deref_open_node() which simpler of_on(). The former takes both @kn and @of and RCU deref @kn->attr.open while sanity checking with @of. The latter takes @of and uses protected deref on of->kn->attr.open. As the return value can't be NULL, remove the error handling in the callers too. This shouldn't cause any functional changes. Cc: Imran Khan <imran.f.khan@oracle.com> Tested-by: Chengming Zhou <zhouchengming@bytedance.com> Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com> Signed-off-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20220828050440.734579-2-tj@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.