On Sun, Oct 17, 2021 at 9:41 PM Christoph Hellwig <hch@xxxxxx> wrote:
>
> Drivers that register a dax_dev should make sure it works, no need
> to double check from the file system.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> drivers/dax/super.c | 49 +--------------------------------------------
> 1 file changed, 1 insertion(+), 48 deletions(-)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 9383c11b21853..04fc680542e8d 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -107,13 +107,9 @@ bool generic_fsdax_supported(struct dax_device *dax_dev,
> struct block_device *bdev, int blocksize, sector_t start,
> sector_t sectors)
> {
> - bool dax_enabled = false;
> pgoff_t pgoff, pgoff_end;
> - void *kaddr, *end_kaddr;
> - pfn_t pfn, end_pfn;
> sector_t last_page;
> - long len, len2;
> - int err, id;
> + int err;
>
> if (blocksize != PAGE_SIZE) {
> pr_info("%pg: error: unsupported blocksize for dax\n", bdev);
> @@ -138,49 +134,6 @@ bool generic_fsdax_supported(struct dax_device *dax_dev,
> return false;
> }
>
> - id = dax_read_lock();
> - len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);
> - len2 = dax_direct_access(dax_dev, pgoff_end, 1, &end_kaddr, &end_pfn);
> -
> - if (len < 1 || len2 < 1) {
> - pr_info("%pg: error: dax access failed (%ld)\n",
> - bdev, len < 1 ? len : len2);
> - dax_read_unlock(id);
> - return false;
> - }
> -
> - if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) {
> - /*
> - * An arch that has enabled the pmem api should also
> - * have its drivers support pfn_t_devmap()
> - *
> - * This is a developer warning and should not trigger in
> - * production. dax_flush() will crash since it depends
> - * on being able to do (page_address(pfn_to_page())).
> - */
> - WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));
> - dax_enabled = true;
> - } else if (pfn_t_devmap(pfn) && pfn_t_devmap(end_pfn)) {
> - struct dev_pagemap *pgmap, *end_pgmap;
> -
> - pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn), NULL);
> - end_pgmap = get_dev_pagemap(pfn_t_to_pfn(end_pfn), NULL);
> - if (pgmap && pgmap == end_pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX
> - && pfn_t_to_page(pfn)->pgmap == pgmap
> - && pfn_t_to_page(end_pfn)->pgmap == pgmap
> - && pfn_t_to_pfn(pfn) == PHYS_PFN(__pa(kaddr))
> - && pfn_t_to_pfn(end_pfn) == PHYS_PFN(__pa(end_kaddr)))
This is effectively a self-test for a regression that was found while
manipulating the 'struct page' memmap metadata reservation for PMEM
namespaces.
I guess it's just serving as a security-blanket now and I should find
a way to move it out to a self-test. I'll take a look.
> - dax_enabled = true;
> - put_dev_pagemap(pgmap);
> - put_dev_pagemap(end_pgmap);
> -
> - }
> - dax_read_unlock(id);
> -
> - if (!dax_enabled) {
> - pr_info("%pg: error: dax support not enabled\n", bdev);
> - return false;
> - }
> return true;
> }
> EXPORT_SYMBOL_GPL(generic_fsdax_supported);
> --
> 2.30.2
>
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