linux-ext4 - Re: [PATCH 05/11] dax: move the partition alignment check into fs_dax_get_by

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Message-ID: <CAPcyv4iqkLQWEyqRYZPaBmA=bXyJy5DR699ch+wfBanY-MKu9g@mail.gmail.com>
Date:   Wed, 27 Oct 2021 16:07:07 -0700
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 05/11] dax: move the partition alignment check into fs_dax_get_by_bdev

On Sun, Oct 17, 2021 at 9:41 PM Christoph Hellwig <hch@....de> wrote:
>
> fs_dax_get_by_bdev is the primary interface to find a dax device for a
> block device, so move the partition alignment check there instead of
> wiring it up through ->dax_supported.

Looks good.

>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  drivers/dax/super.c | 23 ++++++-----------------
>  1 file changed, 6 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 04fc680542e8d..482fe775324a4 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -93,6 +93,12 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
>         if (!blk_queue_dax(bdev->bd_disk->queue))
>                 return NULL;
>
> +       if ((get_start_sect(bdev) * SECTOR_SIZE) % PAGE_SIZE ||
> +           (bdev_nr_sectors(bdev) * SECTOR_SIZE) % PAGE_SIZE) {
> +               pr_info("%pg: error: unaligned partition for dax\n", bdev);
> +               return NULL;
> +       }
> +
>         id = dax_read_lock();
>         dax_dev = xa_load(&dax_hosts, (unsigned long)bdev->bd_disk);
>         if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
> @@ -107,10 +113,6 @@ bool generic_fsdax_supported(struct dax_device *dax_dev,
>                 struct block_device *bdev, int blocksize, sector_t start,
>                 sector_t sectors)
>  {
> -       pgoff_t pgoff, pgoff_end;
> -       sector_t last_page;
> -       int err;
> -
>         if (blocksize != PAGE_SIZE) {
>                 pr_info("%pg: error: unsupported blocksize for dax\n", bdev);
>                 return false;
> @@ -121,19 +123,6 @@ bool generic_fsdax_supported(struct dax_device *dax_dev,
>                 return false;
>         }
>
> -       err = bdev_dax_pgoff(bdev, start, PAGE_SIZE, &pgoff);
> -       if (err) {
> -               pr_info("%pg: error: unaligned partition for dax\n", bdev);
> -               return false;
> -       }
> -
> -       last_page = PFN_DOWN((start + sectors - 1) * 512) * PAGE_SIZE / 512;
> -       err = bdev_dax_pgoff(bdev, last_page, PAGE_SIZE, &pgoff_end);
> -       if (err) {
> -               pr_info("%pg: error: unaligned partition for dax\n", bdev);
> -               return false;
> -       }
> -
>         return true;
>  }
>  EXPORT_SYMBOL_GPL(generic_fsdax_supported);
> --
> 2.30.2
>