linux-kernel - Re: [PATCH 2/2] i915: do not leak module ref counter

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Message-ID: <20190802133503.GA18318@tigerII.localdomain>
Date:   Fri, 2 Aug 2019 22:35:03 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH 2/2] i915: do not leak module ref counter

On (08/02/19 22:15), Sergey Senozhatsky wrote:
[..]
> > > Looking around, it looks like we always need to drop type after
> > > mounting. Should the
> > >         put_filesystem(type);
> > > be here instead?
> > > 
> > > Anyway, nice catch.
> > 
> > Sigh. put_filesystem() is part of fs internals. I'd be tempted to add
> 
> Good catch!
> 
> So we can switch to vfs_kern_mount(), I guess, but pass different options,
> depending on has_transparent_hugepage().

Hmm. This doesn't look exactly right. It appears that vfs_kern_mount()
has a slightly different purpose. It's for drivers which register their
own fstype and fs_context/sb callbacks. A typical usage would be

	static struct file_system_type nfsd_fs_type = {
		.owner→ →       = THIS_MODULE,
		.name→  →       = "nfsd",
		.init_fs_context = nfsd_init_fs_context,
		.kill_sb→       = nfsd_umount,
	};
	MODULE_ALIAS_FS("nfsd");

	vfs_kern_mount(&nfsd_fs_type, SB_KERNMOUNT, "nfsd", NULL);

i915 is a different beast, it just wants to mount fs and reconfigure
it, it doesn't want to be an fs. So it seems that current kern_mount()
is actually right.

Maybe we need to export put_filesystem() instead.

	-ss