linux-kernel - Re: [PATCH v3 3/3] fsdax: Output address in dax_iomap

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Date:   Tue, 25 May 2021 16:12:54 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc:     linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
        darrick.wong@...cle.com, dan.j.williams@...el.com,
        willy@...radead.org, jack@...e.cz, viro@...iv.linux.org.uk,
        linux-btrfs@...r.kernel.org, david@...morbit.com, hch@....de,
        rgoldwyn@...e.de, Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: Re: [PATCH v3 3/3] fsdax: Output address in dax_iomap_pfn() and
 rename it

On Thu, Apr 22, 2021 at 09:45:01PM +0800, Shiyang Ruan wrote:
> Add address output in dax_iomap_pfn() in order to perform a memcpy() in
> CoW case.  Since this function both output address and pfn, rename it to
> dax_iomap_direct_access().
> 
> Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Ritesh Harjani <riteshh@...ux.ibm.com>

Looks pretty simple to me,
Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D

> ---
>  fs/dax.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index f99e33de2036..48a97905c0c3 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -998,8 +998,8 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
>  	return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
>  }
>  
> -static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
> -			 pfn_t *pfnp)
> +static int dax_iomap_direct_access(struct iomap *iomap, loff_t pos, size_t size,
> +		void **kaddr, pfn_t *pfnp)
>  {
>  	const sector_t sector = dax_iomap_sector(iomap, pos);
>  	pgoff_t pgoff;
> @@ -1011,11 +1011,13 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
>  		return rc;
>  	id = dax_read_lock();
>  	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
> -				   NULL, pfnp);
> +				   kaddr, pfnp);
>  	if (length < 0) {
>  		rc = length;
>  		goto out;
>  	}
> +	if (!pfnp)
> +		goto out_check_addr;
>  	rc = -EINVAL;
>  	if (PFN_PHYS(length) < size)
>  		goto out;
> @@ -1025,6 +1027,12 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
>  	if (length > 1 && !pfn_t_devmap(*pfnp))
>  		goto out;
>  	rc = 0;
> +
> +out_check_addr:
> +	if (!kaddr)
> +		goto out;
> +	if (!*kaddr)
> +		rc = -EFAULT;
>  out:
>  	dax_read_unlock(id);
>  	return rc;
> @@ -1389,7 +1397,7 @@ static vm_fault_t dax_fault_actor(struct vm_fault *vmf, pfn_t *pfnp,
>  		return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS;
>  	}
>  
> -	err = dax_iomap_pfn(iomap, pos, size, &pfn);
> +	err = dax_iomap_direct_access(iomap, pos, size, NULL, &pfn);
>  	if (err)
>  		return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err);
>  
> -- 
> 2.31.1
> 
> 
>