linux-kernel - Re: [PATCH v2 0/6] kaddr and pfn can be NULL to ->direct

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Message-ID: <20180725172316.GA12896@linux.intel.com>
Date:   Wed, 25 Jul 2018 11:23:16 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Huaisheng Ye <yehs2007@...o.com>
Cc:     linux-nvdimm@...ts.01.org, dan.j.williams@...el.com,
        ross.zwisler@...ux.intel.com, willy@...radead.org,
        vishal.l.verma@...el.com, dave.jiang@...el.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        viro@...iv.linux.org.uk, martin.petersen@...cle.com,
        axboe@...nel.dk, gregkh@...uxfoundation.org,
        bart.vanassche@....com, jack@...e.cz, agk@...hat.com,
        snitzer@...hat.com, dm-devel@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, chengnt@...ovo.com, colyli@...e.de,
        Huaisheng Ye <yehs1@...ovo.com>
Subject: Re: [PATCH v2 0/6] kaddr and pfn can be NULL to ->direct_access()

On Thu, Jul 26, 2018 at 12:28:43AM +0800, Huaisheng Ye wrote:
> From: Huaisheng Ye <yehs1@...ovo.com>
> 
> Changes since v1 [1]:
> * Involve the previous patches for pfn can be NULL.
> * Reword the patch descriptions according to Christian's comment.
> * According to Ross's suggestion, replace local pointer dummy_addr
>   with NULL within md/dm-writecache for direct_access.
> 
> [1]: https://lkml.org/lkml/2018/7/24/199
> 
> Some functions within fs/dax, dax/super and md/dm-writecache don't
> need to get local pointer kaddr or variable pfn from direct_access.
> Assigning NULL to kaddr or pfn to ->direct_access() is more
> straightforward and simple than offering a useless local pointer or
> variable.
> 
> So all ->direct_access() need to check the validity of pointer kaddr
> and pfn for NULL assignment. If either of them is equal to NULL, that
> is to say callers may have no need for kaddr or pfn, so this series of
> patch are prepared for allowing them to pass in NULL instead of having
> to pass in a local pointer or variable that they then just throw away.

Looks good.  For the series:

Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>