linux-kernel - Re: [PATCH v4 2/9] x86: support kmap_atomic_pfn

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Message-ID: <20150610121202.GA9190@lst.de>
Date:	Wed, 10 Jun 2015 14:12:02 +0200
From:	Christoph Hellwig <hch@....de>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	linux-kernel@...r.kernel.org, axboe@...nel.dk, boaz@...xistor.com,
	david@...morbit.com, linux-arch@...r.kernel.org, arnd@...db.de,
	ross.zwisler@...ux.intel.com, linux-nvdimm@...ts.01.org,
	benh@...nel.crashing.org, linux-fsdevel@...r.kernel.org,
	heiko.carstens@...ibm.com, hch@....de, tj@...nel.org,
	paulus@...ba.org, hpa@...or.com, schwidefsky@...ibm.com,
	willy@...ux.intel.com, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, mingo@...nel.org
Subject: Re: [PATCH v4 2/9] x86: support kmap_atomic_pfn_t() for persistent
	memory

Btw, I don't think this actually is safe without refcounting your kmap
structure.

The driver model ->remove callback can be called at any time, which
will ioremap the memory and remap the kmap structure.  But at this
point a user might still be using it.
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