[PATCH 4.17 49/56] dax: check for QUEUE_FLAG_DAX in bdev_dax_supported()

[Greg Kroah-Hartman]

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>

commit 15256f6cc4b44f2e70503758150267fd2a53c0d6 upstream.

Add an explicit check for QUEUE_FLAG_DAX to __bdev_dax_supported().  This
is needed for DM configurations where the first element in the dm-linear or
dm-stripe target supports DAX, but other elements do not.  Without this
check __bdev_dax_supported() will pass for such devices, letting a
filesystem on that device mount with the DAX option.

Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Suggested-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Fixes: commit 545ed20e6df6 ("dm: add infrastructure for DAX support")
Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Toshi Kani <toshi.kani@xxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>


---
 drivers/dax/super.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -85,6 +85,7 @@ EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
 bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
 {
 	struct dax_device *dax_dev;
+	struct request_queue *q;
 	pgoff_t pgoff;
 	int err, id;
 	void *kaddr;
@@ -97,6 +98,13 @@ bool __bdev_dax_supported(struct block_d
 				bdevname(bdev, buf));
 		return false;
 	}
+
+	q = bdev_get_queue(bdev);
+	if (!q || !blk_queue_dax(q)) {
+		pr_debug("%s: error: request queue doesn't support dax\n",
+				bdevname(bdev, buf));
+		return false;
+	}
 
 	err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff);
 	if (err) {