Messages in this thread | | | Date | Wed, 31 Jan 2024 22:21:27 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH v2 4/7] tracefs: dentry lookup crapectomy |
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On Thu, 1 Feb 2024 03:02:05 +0000 Al Viro <viro@zeniv.linux.org.uk> wrote:
> > 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?
We (Linus and I) got it wrong. It originally had:
d_add(dentry, NULL); [..] return NULL;
and it caused the:
# ls events/kprobes/sched/ ls: cannot access 'events/kprobes/sched/': No such file or directory
# echo 'p:sched schedule' >> /sys/kernel/tracing/kprobe_events # ls events/kprobes/sched/ ls: cannot access 'events/kprobes/sched/': No such file or directory
I just changed the code to simply return NULL, and it had no issues:
# ls events/kprobes/sched/ ls: cannot access 'events/kprobes/sched/': No such file or directory
# echo 'p:sched schedule' >> /sys/kernel/tracing/kprobe_events # ls events/kprobes/sched/ enable filter format hist hist_debug id inject trigger
But then I added the: d_add(dentry, NULL); that we originally had, and then it caused the issue again.
So it wasn't the returning NULL that was causing a problem, it was calling the d_add(dentry, NULL); that was.
I'll update the patch.
-- Steve
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