linux-kernel - Re: [GIT PULL] bcachefs fixes for 6.15-rc4

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Message-ID: <opsx7zniuyrf5uef3x4vbmbusu34ymdt5myyq47ajiefigrg4n@ky74wpog4gr4>
Date: Fri, 25 Apr 2025 23:59:46 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-bcachefs@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] bcachefs fixes for 6.15-rc4

On Fri, Apr 25, 2025 at 08:40:48PM -0700, Linus Torvalds wrote:
> On Fri, 25 Apr 2025 at 20:09, Kent Overstreet <kent.overstreet@...ux.dev> wrote:
> >
> > The subject is CI lookups, and I'll eat my shoe if you wrote that.
> 
> Start chomping. That nasty code with d_compare and d_hash goes way back.
> 
> From a quick look, it's from '97, and got merged in in 2.1.50. It was
> added (obviously) for FAT. Back then, that was the only case that
> wanted it.
> 
> I don't have any archives from that time, and I'm sure others were
> involved, but that whole init_name_hash / partial_name_hash /
> end_name_hash pattern in 2.1.50 looks like code I remember. So I was
> at least part of it.
> 
> The design, if you haven't figured it out yet, is that filesystems
> that have case-independent name comparisons can do their own hash
> functions and their own name comparison functions, exactly so that one
> dentry can match multiple different strings (and different strings can
> hash to the same bucket).
> 
> If you get dentry aliases, you may be doing something wrong.

Yeah, Al just pointed me at generic_set_sb_d_ops().

Which is a perverse way to hide an ops struct. Bloody hell...