On Wed, Jan 31, 2024 at 09:26:42PM -0500, Steven Rostedt wrote: > > Huh? Just return NULL and be done with that - you'll get an > > unhashed negative dentry and let the caller turn that into > > -ENOENT... > > We had a problem here with just returning NULL. It leaves the negative > dentry around and doesn't get refreshed. Why would that dentry stick around? And how would anyone find it, anyway, when it's not hashed? > I did this: > > # cd /sys/kernel/tracing > # ls events/kprobes/sched/ > ls: cannot access 'events/kprobes/sched/': No such file or directory > # echo 'p:sched schedule' >> kprobe_events > # ls events/kprobes/sched/ > ls: cannot access 'events/kprobes/sched/': No such file or directory > > When it should have been: > > # ls events/kprobes/sched/ > enable filter format hist hist_debug id inject trigger > > Leaving the negative dentry there will have it fail when the directory > exists the next time. Then you have something very deeply fucked up. NULL or ERR_PTR(-ENOENT) from ->lookup() in the last component of open() would do exactly the same thing: dput() whatever had been passed to ->lookup() and fail open(2) with -ENOENT.
