[05/29] dax: remove the pgmap sanity checks in generic_fsdax_supported

Commit Message

Christoph Hellwig Nov. 9, 2021, 8:32 a.m. UTC

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 <[e-mail]>
---
 drivers/dax/super.c | 49 +--------------------------------------------
 1 file changed, 1 insertion(+), 48 deletions(-)

Comments

Dan Williams Nov. 23, 2021, 3:35 a.m. UTC | #1

On Tue, Nov 9, 2021 at 12:33 AM Christoph Hellwig <[e-mail]> wrote:
>
> Drivers that register a dax_dev should make sure it works, no need
> to double check from the file system.

Reviewed-by: Dan Williams <[e-mail]>

...with a self-reminder to migrate this validation to a unit test to
backstop any future refactoring of the memmap reservation code.

Patch

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)))
-			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);