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

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Message-ID: <3689520a-4a49-4e1f-6ee9-2ff4a9796b9f@intel.com>
Date:   Wed, 25 Jul 2018 14:35:32 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Huaisheng Ye <yehs2007@...o.com>, linux-nvdimm@...ts.01.org,
        dan.j.williams@...el.com
Cc:     ross.zwisler@...ux.intel.com, willy@...radead.org,
        vishal.l.verma@...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()

Pretty straight forward series. Huaisheng, I can apply the whole series
to libnvdimm if we can get ack's from maintainer of dcssblk and
dm-writecache for the respective bits.

On 07/25/2018 09:28 AM, 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.
> 
> Huaisheng Ye (6):
>   libnvdimm, pmem: kaddr and pfn can be NULL to ->direct_access()
>   s390, dcssblk: kaddr and pfn can be NULL to ->direct_access()
>   tools/testing/nvdimm: kaddr and pfn can be NULL to ->direct_access()
>   dax/super: Do not request a pointer kaddr when not required
>   md/dm-writecache: Don't request pointer dummy_addr when not required
>   filesystem-dax: Do not request kaddr and pfn when not required
> 
>  drivers/dax/super.c             |  3 +--
>  drivers/md/dm-writecache.c      |  3 +--
>  drivers/nvdimm/pmem.c           |  7 +++++--
>  drivers/s390/block/dcssblk.c    |  8 +++++---
>  fs/dax.c                        | 13 ++++---------
>  tools/testing/nvdimm/pmem-dax.c | 12 ++++++++----
>  6 files changed, 24 insertions(+), 22 deletions(-)
>