kernfs: avoid READ_ONCE() on a kgid_t in kernfs_new_node()

kernfs_new_node() reads the parent's gid with READ_ONCE(attrs->ia_gid).
That gid is a kgid_t, which is a struct.

On SMP alpha, READ_ONCE() ends by casting the value it loaded back to
the type of its argument. Here that is a cast from a struct to the same
struct. GCC accepts that as an extension, but ISO C does not allow a
cast to or from a struct type, so sparse warns:

  fs/kernfs/dir.c:751:31: sparse: sparse: cast to non-scalar
  fs/kernfs/dir.c:751:31: sparse: sparse: cast from non-scalar

Read the gid_t inside the kgid_t instead, and wrap it back up with
KGIDT_INIT(). This is still a single marked load of the same four bytes.

There is no functional change. With GCC 12 for alpha (the config from
the report) and GCC 14 for x86-64 (with and without KCSAN),
fs/kernfs/dir.o has the same object code before and after this change.

Fixes: 81bdc85b4c08 ("kernfs: fix up the unlocked attribute reads on the creation paths")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202610261608.vItiXCGW-lkp@intel.com/
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://patch.msgid.link/20261027143247.3537239-1-shakeel.butt@linux.dev
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

0 files changed, 0 insertions, 0 deletions