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From: "Winkler, Tomas" <tomas.winkler@intel.com>
To: Richard Weinberger <richard@nod.at>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
	linux-mtd <linux-mtd@lists.infradead.org>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>
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

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

WARNING: multiple messages have this Message-ID (diff)
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


  reply	other threads:[~2021-01-28  6:34 UTC|newest]

Thread overview: 25+ 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 20:03 ` Tomas Winkler
2021-01-27 20:46 ` Richard Weinberger
2021-01-27 20:46   ` Richard Weinberger
2021-01-27 20:55   ` Winkler, Tomas
2021-01-27 20:55     ` Winkler, Tomas
2021-01-27 21:17     ` Richard Weinberger
2021-01-27 21:17       ` Richard Weinberger
2021-01-28  6:33       ` Winkler, Tomas [this message]
2021-01-28  6:33         ` Winkler, Tomas
2021-01-28  7:47         ` Richard Weinberger
2021-01-28  7:47           ` Richard Weinberger
2021-01-28  8:53           ` Winkler, Tomas
2021-01-28  8:53             ` Winkler, Tomas
2021-01-28  9:00             ` Miquel Raynal
2021-01-28  9:00               ` Miquel Raynal
2021-01-28 17:57               ` Winkler, Tomas
2021-01-28 17:57                 ` Winkler, Tomas
2021-01-28 20:23                 ` Richard Weinberger
2021-01-28 20:23                   ` Richard Weinberger
2021-01-29 16:12                   ` Winkler, Tomas
2021-02-13 17:09                   ` Winkler, Tomas
2021-02-13 17:09                     ` Winkler, Tomas
2021-02-15 13:43                     ` Richard Weinberger
2021-02-15 13:43                       ` Richard Weinberger

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