Re: [PATCH] nvmet: fix the use of ZERO_PAGE in nvme_execute_identify_ns_nvm()

[Keith Busch <kbusch@kernel.org>]

On Fri, Nov 22, 2024 at 01:08:28PM +0100, Christoph Hellwig wrote:
> On Fri, Nov 22, 2024 at 02:20:36PM +0530, Nilay Shroff wrote:
> > The nvme_execute_identify_ns_nvm function uses ZERO_PAGE
> > for copying SG list with all zeros. As ZERO_PAGE would not
> > necessarily return the virtual-address of the zero page, we
> > need to first convert the page address to kernel virtual-
> > address and then use it as source address for copying the
> > data to SG list with all zeros.
> > 
> > Using return address of ZERO_PAGE(0) as source address for
> > copying data to SG list would fill the target buffer with
> > random value and causes the undesired side effect. This patch
> > implements the fix ensuring that we use virtual-address of the
> > zero page for copying all zeros to the SG list buffers.
> 
> I wonder if using ZERO_PAGE() is simply a little too smart for it's
> own sake and it should just use kzalloc like a bunch of other identify
> implementation..

Sure. That'll make it easier to report non-zero values if we decide to
implement a non-stubbed version of this identification later.