linux-kernel - RE: [PATCH] eventfs: Have inodes have unique inode numbers

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Message-ID: <9b34c04465ff46dba90c81b4240fbbd1@AcuMS.aculab.com>
Date: Sat, 27 Jan 2024 15:26:51 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Linus Torvalds' <torvalds@...ux-foundation.org>, Steven Rostedt
	<rostedt@...dmis.org>
CC: LKML <linux-kernel@...r.kernel.org>, Linux Trace Devel
	<linux-trace-devel@...r.kernel.org>, Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Christian Brauner
	<brauner@...nel.org>, Ajay Kaher <ajay.kaher@...adcom.com>, "Geert
 Uytterhoeven" <geert@...ux-m68k.org>, linux-fsdevel
	<linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH] eventfs: Have inodes have unique inode numbers

From: Linus Torvalds
> Sent: 26 January 2024 21:36
> 
> On Fri, 26 Jan 2024 at 13:26, Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > I'd be happy to change that patch to what I originally did before deciding
> > to copy get_next_ino():
> >
> > unsigned int tracefs_get_next_ino(int files)
> > {
> >         static atomic_t next_inode;
> >         unsigned int res;
> >
> >         do {
> >                 res = atomic_add_return(files + 1, &next_inode);
> >
> >                 /* Check for overflow */
> >         } while (unlikely(res < files + 1));
> >
> >         return res - files;
> 
> Still entirely pointless.
> 
> If you have more than 4 billion inodes, something is really really wrong.
> 
> So why is it ten lines instead of one?

Doesn't Linux support 64bit inode numbers?
They solve the wrap problem...

I also don't know what filesystems like NTFS use - they don't have
the concept of inode.

IIRC NFS used to use the inode number for its 'file handle'.
Rather a pain when trying to write code to export a layered FS
(especially if a layer might be an NFS mount!).

	David

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