Re: [PATCH] btrfs: test create a bunch of files with name hash collision

[Christoph Hellwig <hch@infradead.org>]

On Fri, Mar 06, 2026 at 02:55:23PM +0000, Filipe Manana wrote:
> > Umm, file systems must handle an unlimited number of name collisions.
> > While going read-only is of course really bad, just rejecting them
> > can also pretty easily break things.
> 
> I don't think in practice we get a large enough number of names with a
> crc32c hash collision in btrfs.

That's not the point.  Posix and Linux file systems don't have an
error code or defined condition for adding this file name would cause
a hash collision and we were to lazy to deal with it.

> Adding support for an unlimited number of collisions is simply not
> easily doable, it would require an on-disk format change (new key
> type, item, etc, update btrfs-progs, etc).
> The motivation for that is very low, as I'm not aware of users ever complaining.

Well, how would they know this happened?  The users only sees the file
system acting weird in completely unpredictable ways.