Re: [PATCH 06/29] dax: move the partition alignment check into fs_dax_get_by_bdev

Darrick J. Wong
2021-11-23T22:26:00Z

On Tue, Nov 09, 2021 at 09:32:46AM +0100, Christoph Hellwig 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.
>
> Signed-off-by: Christoph Hellwig <hch@lst.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) {

Do we have to be careful about 64-bit division here, or do we not
support DAX on 32-bit?

> + pr_info("%pg: error: unaligned partition for dax\n", bdev);

I also wonder if this should be ratelimited...?

--D

> + 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
>