Re: [PATCH v6 5/6] tracing: Show inode and device major:minor in deferred user space stacktrace

[Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>]

On August 28, 2025 3:39:35 PM GMT-03:00, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>On Thu, 28 Aug 2025 at 11:05, Steven Rostedt <rostedt@kernel.org> wrote:
>>
>> The deferred user space stacktrace event already does a lookup of the vma
>> for each address in the trace to get the file offset for those addresses,
>> it can also report the file itself.
>
>That sounds like a good idea..
>
>But the implementation absolutely sucks:
>
>> Add two more arrays to the user space stacktrace event. One for the inode
>> number, and the other to store the device major:minor number. Now the
>> output looks like this:
>
>WTF? Why are you back in the 1960's? What's next? The index into the
>paper card deck?
>
>Stop using inode numbers and device numbers already. It's the 21st
>century. No, cars still don't fly, but dammit, inode numbers were a
>great idea back in the days, but they are not acceptable any more.
>
>They *particularly* aren't acceptable when you apparently think that
>they are 'unsigned long'.  Yes, that's the internal representation we
>use for inode indexing, but for example on nfs the inode is actually
>bigger. It's exposed to user space as a u64 through
>
>        stat->ino = nfs_compat_user_ino64(NFS_FILEID(inode));
>
>so the inode that user space sees in 'struct stat' (a) doesn't
>actually match inode->i_ino, and (b) isn't even the full file ID that
>NFS actually uses.
>
>Let's not let that 60's thinking be any part of a new interface.
>
>Give the damn thing an actual filename or something *useful*, not a
>number that user space can't even necessarily match up to anything.
>

A build ID?

PERF_RECORD_MMAP went thru this, filename ->  inode -> Content based hash

- Arnaldo