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 11:35:43 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Mike Snitzer <snitzer@...hat.com>, Ira Weiny <ira.weiny@...el.com>,
        device-mapper development <dm-devel@...hat.com>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        Linux NVDIMM <nvdimm@...ts.linux.dev>,
        linux-s390 <linux-s390@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-erofs@...ts.ozlabs.org,
        linux-ext4 <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 9, 2021 at 12:33 AM Christoph Hellwig <hch@....de> 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.

Looks good,

Reviewed-by: Dan Williams <dan.j.williams@...el.com>

>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  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
>