pmem, dax: disable dax in the presence of bad blocks

Longer term teach dax to punch "error" holes in mapping requests and
deliver SIGBUS to applications that consume a bad pmem page.  For now,
simply disable the dax performance optimization in the presence of known
errors.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

block/ioctl.c

@@ -4,6 +4,7 @@
 #include <linux/gfp.h>
 #include <linux/blkpg.h>
 #include <linux/hdreg.h>
+#include <linux/badblocks.h>
 #include <linux/backing-dev.h>
 #include <linux/fs.h>
 #include <linux/blktrace_api.h>
@@ -422,6 +423,15 @@ bool blkdev_dax_capable(struct block_device *bdev)
 			|| (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
 		return false;
 
+	/*
+	 * If the device has known bad blocks, force all I/O through the
+	 * driver / page cache.
+	 *
+	 * TODO: support finer grained dax error handling
+	 */
+	if (disk->bb && disk->bb->count)
+		return false;
+
 	return true;
 }
 

drivers/nvdimm/pmem.c

@@ -233,6 +233,7 @@ static int pmem_attach_disk(struct device *dev,
 		return -ENOMEM;
 	nvdimm_namespace_add_poison(ndns, &pmem->bb, pmem->data_offset);
 
+	disk->bb = &pmem->bb;
 	add_disk(disk);
 	revalidate_disk(disk);