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Date:   Wed, 25 Jul 2018 11:23:16 -0600
From:   Ross Zwisler <ross.zwisler@linux.intel.com>
To:     Huaisheng Ye <yehs2007@zoho.com>
Cc:     linux-nvdimm@lists.01.org, dan.j.williams@intel.com,
        ross.zwisler@linux.intel.com, willy@infradead.org,
        vishal.l.verma@intel.com, dave.jiang@intel.com,
        schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
        viro@zeniv.linux.org.uk, martin.petersen@oracle.com,
        axboe@kernel.dk, gregkh@linuxfoundation.org,
        bart.vanassche@wdc.com, jack@suse.cz, agk@redhat.com,
        snitzer@redhat.com, dm-devel@redhat.com,
        linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, chengnt@lenovo.com, colyli@suse.de,
        Huaisheng Ye <yehs1@lenovo.com>
Subject: Re: [PATCH v2 0/6] kaddr and pfn can be NULL to ->direct_access()
Message-ID: <20180725172316.GA12896@linux.intel.com>
Mail-Followup-To: Ross Zwisler <ross.zwisler@linux.intel.com>,
        Huaisheng Ye <yehs2007@zoho.com>, linux-nvdimm@lists.01.org,
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        vishal.l.verma@intel.com, dave.jiang@intel.com,
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        axboe@kernel.dk, gregkh@linuxfoundation.org, bart.vanassche@wdc.com,
        jack@suse.cz, agk@redhat.com, snitzer@redhat.com,
        dm-devel@redhat.com, linux-kernel@vger.kernel.org,
        linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        chengnt@lenovo.com, colyli@suse.de, Huaisheng Ye <yehs1@lenovo.com>
References: <20180725162849.8320-1-yehs2007@zoho.com>
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On Thu, Jul 26, 2018 at 12:28:43AM +0800, Huaisheng Ye wrote:
> From: Huaisheng Ye <yehs1@lenovo.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@linux.intel.com>