linux-kernel - Re: [PATCH 00/20] filelock: split struct file_lock into file_lock and file

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Date: Thu, 18 Jan 2024 05:59:04 +1100
From: "NeilBrown" <neilb@...e.de>
To: "Chuck Lever" <chuck.lever@...cle.com>
Cc: "Jeff Layton" <jlayton@...nel.org>,
 "Christian Brauner" <brauner@...nel.org>,
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Subject: Re: [PATCH 00/20] filelock: split struct file_lock into file_lock and
 file_lease structs

On Thu, 18 Jan 2024, Chuck Lever wrote:
> On Tue, Jan 16, 2024 at 02:45:56PM -0500, Jeff Layton wrote:
> > Long ago, file locks used to hang off of a singly-linked list in struct
> > inode. Because of this, when leases were added, they were added to the
> > same list and so they had to be tracked using the same sort of
> > structure.
> > 
> > Several years ago, we added struct file_lock_context, which allowed us
> > to use separate lists to track different types of file locks. Given
> > that, leases no longer need to be tracked using struct file_lock.
> > 
> > That said, a lot of the underlying infrastructure _is_ the same between
> > file leases and locks, so we can't completely separate everything.
> 
> Naive question: locks and leases are similar. Why do they need to be
> split apart? The cover letter doesn't address that, and I'm new
> enough at this that I don't have that context.

For me, the big win was in the last patch where we got separate
lock_manager_operations and lease_manager_operations.  There is zero
overlap between the two.  This highlights that one one level these are
different things with different behaviours.

NeilBrown