> -----Original Message----- > From: Greg Kroah-Hartman <[email protected]> > Sent: Thursday, May 14, 2026 3:00 PM > To: Justin He <[email protected]> > Cc: [email protected]; [email protected]; linux-perf- > [email protected]; [email protected]; kunit- > [email protected]; [email protected]; linux- > [email protected]; Arnd Bergmann <[email protected]>; Alexander Viro > <[email protected]>; Christian Brauner <[email protected]>; Jan Kara > <[email protected]>; Peter Zijlstra <[email protected]>; Ingo Molnar > <[email protected]>; Arnaldo Carvalho de Melo <[email protected]>; > Namhyung Kim <[email protected]>; Mark Rutland > <[email protected]>; Alexander Shishkin > <[email protected]>; Jiri Olsa <[email protected]>; Ian > Rogers <[email protected]>; Adrian Hunter <[email protected]>; > James Clark <[email protected]>; Brendan Higgins > <[email protected]>; David Gow <[email protected]>; Rae Moar > <[email protected]>; Alexander Potapenko <[email protected]>; > Marco Elver <[email protected]>; Dmitry Vyukov <[email protected]>; > Andrew Morton <[email protected]>; Paul E. McKenney > <[email protected]>; Petr Mladek <[email protected]>; Kees Cook > <[email protected]>; David Disseldorp <[email protected]> > Subject: Re: [PATCH 5/7] misc: reject duplicate names in misc_register() > > On Thu, May 14, 2026 at 05:04:53AM +0000, Jia He wrote: > > The miscdev kunit suite registers two miscdevices with the same name > > and expects -EEXIST. The second call currently goes all the way to > > sysfs_create_dir_ns(), which prints "cannot create duplicate filename" > > with a backtrace on every run. > > > > Walk misc_list under misc_mtx, return -EEXIST on a name collision and > > free the just-allocated minor before returning. > > > > To: Arnd Bergmann <[email protected]> > > To: Greg Kroah-Hartman <[email protected]> > > This should be Cc: right? > > > > > Signed-off-by: Jia He <[email protected]> > > --- > > drivers/char/misc.c | 22 ++++++++++++++++++++++ > > 1 file changed, 22 insertions(+) > > > > diff --git a/drivers/char/misc.c b/drivers/char/misc.c index > > 726516fb0a3b..d6ffa21ac495 100644 > > --- a/drivers/char/misc.c > > +++ b/drivers/char/misc.c > > @@ -248,6 +248,28 @@ int misc_register(struct miscdevice *misc) > > } > > } > > > > + /* > > + * Detect duplicate names up-front so the subsequent > > + * device_create_with_groups() does not trip > > + * sysfs_create_dir_ns()->sysfs_warn_dup(), which unconditionally > > + * dumps a stack trace. Both the existing miscdev kunit suite > > + * (miscdev_test_duplicate_name) and any caller racing on the same > > + * name would otherwise pollute dmesg on every -EEXIST. > > + */ > > + { > > + struct miscdevice *c; > > + > > + list_for_each_entry(c, &misc_list, list) { > > + if (strcmp(c->name, misc->name) == 0) { > > + misc_minor_free(misc->minor); > > + if (is_dynamic) > > + misc->minor = > MISC_DYNAMIC_MINOR; > > + err = -EEXIST; > > + goto out; > > + } > > + } > > + } > > Don't do additional {} where not needed. > > And as the current code works properly, we are relying on sysfs for the > rejection, why do this now here? The stack dump is good, it shows the > offending caller, so they can fix it up better. So why change this? > Thanks for the feedback. I’ll drop the two patches that silence the sysfs warning for duplicate filenames.
--- Cheers, Justin He(Jia He)
