On Sat, Apr 27, 2024 at 02:40:22PM -0700, Linus Torvalds wrote:
> On Sat, 27 Apr 2024 at 14:11, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > ... eliminating the need to reopen block devices so they could be
> > exclusively held.
>
> This looks like a good change, but it raises the question of why we
> did it this odd way to begin with?
>
> Is it just because O_EXCL without O_CREAT is kind of odd, and only has
> meaning for block devices?
>
> Or is it just that before we used fiel pointers for block devices, the
> old model made more sense?
>
> Anyway, I like it, it just makes me go "why didn't we do it that way
> originally?"
Exclusion for swap partitions:
commit 75e9c9e1bffbe4a1767172855296b94ccba28f71
Author: Alexander Viro <viro@xxxxxxxxxxxx>
Date: Mon Mar 4 22:56:47 2002 -0800
[PATCH] death of is_mounted() and aother fixes
O_EXCL for block devices:
commit c366082d9ed0a0d3c46441d1b3fdf895d8e55ca9
Author: Andrew Morton <akpm@xxxxxxxx>
Date: Wed Aug 20 10:26:57 2003 -0700
[PATCH] Allow O_EXCL on a block device to claim exclusive use.
IOW, O_EXCL hadn't been available at the time - it had been implemented
on top of bd_claim()/bd_release() introduced in the same earlier commit.
Switching swap exclusion to O_EXCL could've been done back in 2003 or
at any later point; it's just that swapon(2)/swapoff(2) is something that
rarely gets a look...
