-Wenum-conversion in fs/cachefiles/namei.c

[nickdesaulniers]

  CC      fs/cachefiles/namei.o
fs/cachefiles/namei.c:247:50: warning: implicit conversion from enumeration type 'enum cachefiles_obj_ref_trace' to different enumeration type 'enum fscache_obj_ref_trace'
      [-Wenum-conversion]
        cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_retry);
        ~~~~~                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/cachefiles/namei.c:251:50: warning: implicit conversion from enumeration type 'enum cachefiles_obj_ref_trace' to different enumeration type 'enum fscache_obj_ref_trace'
      [-Wenum-conversion]
        cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_timeo);
        ~~~~~ 

[nathanchance]

I can't think of a clean way to fix this other than to add an explicit cast like so:

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index af2b17b21b94..15e5988a83de 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -244,11 +244,13 @@ static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
 
        ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags));
 
-       cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_retry);
+       cache->cache.ops->put_object(&xobject->fscache,
+               (enum fscache_obj_ref_trace)cachefiles_obj_put_wait_retry);
        goto try_again;
 
 requeue:
-       cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_timeo);
+       cache->cache.ops->put_object(&xobject->fscache,
+               (enum fscache_obj_ref_trace)cachefiles_obj_put_wait_timeo);
        _leave(" = -ETIMEDOUT");
        return -ETIMEDOUT;
 }

or modify all instances of put_object to just take an int for why which seems entirely unnecessary for this one warning.

Is this even a problem? cachefiles_put_object does explicitly cast why to cachefiles_obj_ref_trace (which is why's only use in that function).

        trace_cachefiles_ref(object, _object->cookie,
                             (enum cachefiles_obj_ref_trace)why, u);

and cachefiles_obj_ref_trace is an extension of fscache_obj_ref_trace:

include/linux/fscache-cache.h:

enum fscache_obj_ref_trace {
        fscache_obj_get_add_to_deps,
        fscache_obj_get_queue,
        fscache_obj_put_alloc_fail,
        fscache_obj_put_attach_fail,
        fscache_obj_put_drop_obj,
        fscache_obj_put_enq_dep,
        fscache_obj_put_queue,
        fscache_obj_put_work,
        fscache_obj_ref__nr_traces
};

include/trace/events/cachefiles.h:

enum cachefiles_obj_ref_trace {
        cachefiles_obj_put_wait_retry = fscache_obj_ref__nr_traces,
        cachefiles_obj_put_wait_timeo,
        cachefiles_obj_ref__nr_traces
};

Seems like this might be worth hiding with a diagnostic. @nickdesaulniers did you ever revist your Clang diagostic patches from #24?

[nathanchance]

Patch sent: https://lore.kernel.org/lkml/20180924173344.27952-1-natechancellor@gmail.com/

[nathanchance]

Merged into mainline: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b7e768b7e3522695ed36dcb48ecdcd344bd30a9b