linux-ext4 - Re: [PATCH 22/29] iomap: add a IOMAP

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Date:   Tue, 23 Nov 2021 18:47:10 -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 22/29] iomap: add a IOMAP_DAX flag

On Tue, Nov 9, 2021 at 12:34 AM Christoph Hellwig <hch@....de> wrote:
>
> Add a flag so that the file system can easily detect DAX operations.

Looks ok, but I would have preferred a quick note about the rationale
here before needing to read other patches to figure that out.

If you add that you can add:

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

>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/dax.c              | 7 ++++---
>  include/linux/iomap.h | 1 +
>  2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 5b52b878124ac..0bd6cdcbacfc4 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1180,7 +1180,7 @@ int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
>                 .inode          = inode,
>                 .pos            = pos,
>                 .len            = len,
> -               .flags          = IOMAP_ZERO,
> +               .flags          = IOMAP_DAX | IOMAP_ZERO,
>         };
>         int ret;
>
> @@ -1308,6 +1308,7 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
>                 .inode          = iocb->ki_filp->f_mapping->host,
>                 .pos            = iocb->ki_pos,
>                 .len            = iov_iter_count(iter),
> +               .flags          = IOMAP_DAX,
>         };
>         loff_t done = 0;
>         int ret;
> @@ -1461,7 +1462,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
>                 .inode          = mapping->host,
>                 .pos            = (loff_t)vmf->pgoff << PAGE_SHIFT,
>                 .len            = PAGE_SIZE,
> -               .flags          = IOMAP_FAULT,
> +               .flags          = IOMAP_DAX | IOMAP_FAULT,
>         };
>         vm_fault_t ret = 0;
>         void *entry;
> @@ -1570,7 +1571,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
>         struct iomap_iter iter = {
>                 .inode          = mapping->host,
>                 .len            = PMD_SIZE,
> -               .flags          = IOMAP_FAULT,
> +               .flags          = IOMAP_DAX | IOMAP_FAULT,
>         };
>         vm_fault_t ret = VM_FAULT_FALLBACK;
>         pgoff_t max_pgoff;
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 6d1b08d0ae930..146a7e3e3ea11 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -141,6 +141,7 @@ struct iomap_page_ops {
>  #define IOMAP_NOWAIT           (1 << 5) /* do not block */
>  #define IOMAP_OVERWRITE_ONLY   (1 << 6) /* only pure overwrites allowed */
>  #define IOMAP_UNSHARE          (1 << 7) /* unshare_file_range */
> +#define IOMAP_DAX              (1 << 8) /* DAX mapping */
>
>  struct iomap_ops {
>         /*
> --
> 2.30.2
>