On Thu, Dec 09, 2021 at 10:40:42PM +0300, Dmitry Osipenko wrote: > External email: Use caution opening links or attachments > > > 09.12.2021 22:32, Nicolin Chen пишет: > > On Thu, Dec 09, 2021 at 05:47:18PM +0300, Dmitry Osipenko wrote: > >> External email: Use caution opening links or attachments > >> > >> > >> 09.12.2021 10:38, Nicolin Chen пишет: > >>> @@ -545,6 +719,15 @@ static void tegra_smmu_detach_as(struct tegra_smmu *smmu, > >>> if (group->swgrp != swgrp) > >>> continue; > >>> group->as = NULL; > >>> + > >>> + if (smmu->debugfs_mappings) { > >> Do we really need this check? > >> > >> Looks like all debugfs_create_dir() usages in this driver are incorrect, > >> that function never returns NULL. Please fix this. > > debugfs_create_dir returns ERR_PTR on failure. So here should be > > to check !IS_ERR. Thanks for pointing it out! > > > > All debugfs functions handle IS_ERR(). GregKH removes all such checks > all over the kernel. So the check shouldn't be needed at all, please > remove it if it's unneeded or prove that it's needed. debugfs_create_file can handle a NULL parent, but not ERR_PTR one, and then it puts the new node under the root. So either passing an ERR_PTR parent or creating orphan nodes here doesn't sound good...