Re: [PATCH v5 2/5] allow mapping page-less memremaped areas into KVA

From: Christoph Hellwig
Date: Thu Aug 13 2015 - 10:41:39 EST

On Thu, Aug 13, 2015 at 04:23:38PM +0300, Boaz Harrosh wrote:
> > DAX as is is races against pmem unbind. A synchronization cost must
> > be paid somewhere to make sure the memremap() mapping is still valid.
> Sorry for being so slow, is what I asked. what is exactly "pmem unbind" ?
> Currently in my 4.1 Kernel the ioremap is done on modprobe time and
> released modprobe --remove time. the --remove can not happen with a mounted
> FS dax or not. So what is exactly "pmem unbind". And if there is a new knob
> then make it refuse with a raised refcount.

Surprise removal of a PCIe card which is mapped to provide non-volatile
memory for example. Or memory hot swap.
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