linux-kernel - Re: [PATCH] [RFC] kernfs: Allow vm_ops->close() if VMA is never split

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Date:   Mon, 13 Jul 2020 09:42:51 +0200 (CEST)
From:   Richard Weinberger <richard@....at>
To:     linux-kernel <linux-kernel@...r.kernel.org>
Cc:     tj@...nel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        ebiederm@...ssion.com, dan j williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] [RFC] kernfs: Allow vm_ops->close() if VMA is never
 split

----- Ursprüngliche Mail -----
> Von: "richard" <richard@....at>
> An: "linux-kernel" <linux-kernel@...r.kernel.org>
> CC: tj@...nel.org, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, ebiederm@...ssion.com, "dan j williams"
> <dan.j.williams@...el.com>, "richard" <richard@....at>
> Gesendet: Samstag, 4. Juli 2020 22:56:19
> Betreff: [PATCH] [RFC] kernfs: Allow vm_ops->close() if VMA is never split

> 10 years ago commit a6849fa1f7d7 ("sysfs: Fail bin file mmap if vma close is
> implemented.")
> removed support for vm_ops->close() for mmap on sysfs.
> As far I understand the reason is that due to the wrapping in kernfs
> every VMA split operation needs to be tracked to call vm_ops->close()
> for all fragments. This is not feasible with reasonable effort.
> 
> Since commit 31383c6865a5 ("mm, hugetlbfs: introduce ->split() to
> vm_operations_struct")
> we can get notified as soon a VMA is split, this can help to relax the
> restriction.
> So I propose to allow having a custom close under the condition that a
> VMA cannot get split.
> 
> Signed-off-by: Richard Weinberger <richard@....at>

*friendly ping*

Thanks,
//richard