linux-kernel - Re: [PATCH 1/7] fsdax: Output address in dax_iomap

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Date:   Mon, 22 Feb 2021 15:44:26 +0800
From:   Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>
To:     Shiyang Ruan <ruansy.fnst@...fujitsu.com>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org
Cc:     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, ocfs2-devel@....oracle.com,
        david@...morbit.com, hch@....de, rgoldwyn@...e.de
Subject: Re: [PATCH 1/7] fsdax: Output address in dax_iomap_pfn() and rename
 it

hi,

> 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@...fujitsu.com>
> ---
>   fs/dax.c | 20 +++++++++++++++-----
>   1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 5b47834f2e1b..b012b2db7ba2 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)
Should this be "if (!*pfnp)"?

Regards,
Xiaoguang Wang
> +		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;
> @@ -1348,7 +1356,8 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
>   			count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
>   			major = VM_FAULT_MAJOR;
>   		}
> -		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
> +		error = dax_iomap_direct_access(&iomap, pos, PAGE_SIZE,
> +						NULL, &pfn);
>   		if (error < 0)
>   			goto error_finish_iomap;
>   
> @@ -1566,7 +1575,8 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
>   
>   	switch (iomap.type) {
>   	case IOMAP_MAPPED:
> -		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
> +		error = dax_iomap_direct_access(&iomap, pos, PMD_SIZE,
> +						NULL, &pfn);
>   		if (error < 0)
>   			goto finish_iomap;
>   
>