From: "Winkler, Tomas" <tomas.winkler@intel.com>
To: Richard Weinberger <richard@nod.at>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-mtd <linux-mtd@lists.infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] mtd: use refcount to prevent corruption
Date: Thu, 28 Jan 2021 06:33:47 +0000 [thread overview]
Message-ID: <a6cb6eb10bbb48989d3a9e087951e50e@intel.com> (raw)
In-Reply-To: <1776363776.325713.1611782270873.JavaMail.zimbra@nod.at>
>
> ----- Ursprüngliche Mail -----
> >> > When underlying device is removed mtd core will crash in case user
> >> > space is still holding an open handle to a mtd device node.
> >> > A proper refcounting is needed so device is release only when a
> >> > partition has no active users. The current simple counter is not
> >> > sufficient.
> >>
> >> Can you please explain a little more what devices are involved?
> >> Does it implement _get_device() and _put_device()?
> > No this is not connected to those handlers of the underlying device
> > and those won't help.
> > I have a spi device provided by MFD framework so it can go away anytime.
>
> Can it go away physically or just in software?
Software, but since this is mfd it's basically hotplug. The kernel is crashing when I simulate hardware failure.
>
> Usually the pattern is that you make sure in the device driver that nobody can
> orphan the MTD while it is in use.
> e.g. drivers/mtd/ubi/gluebi.c does so. In _get_device() it grabs a reference on
> the underlying UBI volume to make sure it cannot go away while the MTD (on
> top of UBI) is in use.
I can try that if it helps, because we are simulating possible lower level crash.
In an case I believe that the proper refcouting is much more robust solution, than the current one.
I'd appreciate if someone can review the actual implementation.
Thanks
Tomas
next prev parent reply other threads:[~2021-01-28 6:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-27 20:03 [PATCH] mtd: use refcount to prevent corruption Tomas Winkler
2021-01-27 20:46 ` Richard Weinberger
2021-01-27 20:55 ` Winkler, Tomas
2021-01-27 21:17 ` Richard Weinberger
2021-01-28 6:33 ` Winkler, Tomas [this message]
2021-01-28 7:47 ` Richard Weinberger
2021-01-28 8:53 ` Winkler, Tomas
2021-01-28 9:00 ` Miquel Raynal
2021-01-28 17:57 ` Winkler, Tomas
2021-01-28 20:23 ` Richard Weinberger
2021-02-13 17:09 ` Winkler, Tomas
2021-02-15 13:43 ` Richard Weinberger
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