linux-ext4 - Re: [PATCH 13/29] fsdax: use a saner calling convention for copy_cow_page

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Date:   Tue, 23 Nov 2021 14:33:52 -0800
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Ira Weiny <ira.weiny@...el.com>, dm-devel@...hat.com,
        linux-xfs@...r.kernel.org, nvdimm@...ts.linux.dev,
        linux-s390@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-erofs@...ts.ozlabs.org, linux-ext4@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 13/29] fsdax: use a saner calling convention for
 copy_cow_page_dax

On Tue, Nov 09, 2021 at 09:32:53AM +0100, Christoph Hellwig wrote:
> Just pass the vm_fault and iomap_iter structures, and figure out the rest
> locally.  Note that this requires moving dax_iomap_sector up in the file.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Yes, nice cleanup!
Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D

> ---
>  fs/dax.c | 29 +++++++++++++----------------
>  1 file changed, 13 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 73bd1439d8089..e51b4129d1b65 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -709,26 +709,31 @@ int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
>  	return __dax_invalidate_entry(mapping, index, false);
>  }
>  
> -static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_dev,
> -			     sector_t sector, struct page *to, unsigned long vaddr)
> +static sector_t dax_iomap_sector(const struct iomap *iomap, loff_t pos)
>  {
> +	return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
> +}
> +
> +static int copy_cow_page_dax(struct vm_fault *vmf, const struct iomap_iter *iter)
> +{
> +	sector_t sector = dax_iomap_sector(&iter->iomap, iter->pos);
>  	void *vto, *kaddr;
>  	pgoff_t pgoff;
>  	long rc;
>  	int id;
>  
> -	rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
> +	rc = bdev_dax_pgoff(iter->iomap.bdev, sector, PAGE_SIZE, &pgoff);
>  	if (rc)
>  		return rc;
>  
>  	id = dax_read_lock();
> -	rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
> +	rc = dax_direct_access(iter->iomap.dax_dev, pgoff, 1, &kaddr, NULL);
>  	if (rc < 0) {
>  		dax_read_unlock(id);
>  		return rc;
>  	}
> -	vto = kmap_atomic(to);
> -	copy_user_page(vto, kaddr, vaddr, to);
> +	vto = kmap_atomic(vmf->cow_page);
> +	copy_user_page(vto, kaddr, vmf->address, vmf->cow_page);
>  	kunmap_atomic(vto);
>  	dax_read_unlock(id);
>  	return 0;
> @@ -1005,11 +1010,6 @@ int dax_writeback_mapping_range(struct address_space *mapping,
>  }
>  EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
>  
> -static sector_t dax_iomap_sector(const struct iomap *iomap, loff_t pos)
> -{
> -	return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
> -}
> -
>  static int dax_iomap_pfn(const struct iomap *iomap, loff_t pos, size_t size,
>  			 pfn_t *pfnp)
>  {
> @@ -1332,19 +1332,16 @@ static vm_fault_t dax_fault_synchronous_pfnp(pfn_t *pfnp, pfn_t pfn)
>  static vm_fault_t dax_fault_cow_page(struct vm_fault *vmf,
>  		const struct iomap_iter *iter)
>  {
> -	sector_t sector = dax_iomap_sector(&iter->iomap, iter->pos);
> -	unsigned long vaddr = vmf->address;
>  	vm_fault_t ret;
>  	int error = 0;
>  
>  	switch (iter->iomap.type) {
>  	case IOMAP_HOLE:
>  	case IOMAP_UNWRITTEN:
> -		clear_user_highpage(vmf->cow_page, vaddr);
> +		clear_user_highpage(vmf->cow_page, vmf->address);
>  		break;
>  	case IOMAP_MAPPED:
> -		error = copy_cow_page_dax(iter->iomap.bdev, iter->iomap.dax_dev,
> -					  sector, vmf->cow_page, vaddr);
> +		error = copy_cow_page_dax(vmf, iter);
>  		break;
>  	default:
>  		WARN_ON_ONCE(1);
> -- 
> 2.30.2
>