Re: [PATCH 2/7] block: align the bio after building it

On 8/4/25 16:08, Keith Busch wrote:

On Mon, Aug 04, 2025 at 08:54:00AM +0200, Hannes Reinecke wrote:

quoted

On 8/2/25 01:47, Keith Busch wrote:

quoted

+static int bio_align_to_lbs(struct bio *bio, struct iov_iter *iter)
+{
+	struct block_device *bdev = bio->bi_bdev;
+	size_t nbytes;
+
+	if (!bdev)
+		return 0;
+
+	nbytes = bio->bi_iter.bi_size & (bdev_logical_block_size(bdev) - 1);
+	if (!nbytes)
+		return 0;
+
+	bio_revert(bio, nbytes);
+	iov_iter_revert(iter, nbytes);
+	if (!bio->bi_iter.bi_size)
+		return -EFAULT;
+
+	return 0;
+}
+
   /**
    * bio_iov_iter_get_pages - add user or kernel pages to a bio
    * @bio: bio to add pages to

@@ -1336,6 +1355,7 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
   		ret = __bio_iov_iter_get_pages(bio, iter);
   	} while (!ret && iov_iter_count(iter) && !bio_full(bio, 0));
+	ret = bio_align_to_lbs(bio, iter);
   	return bio->bi_vcnt ? 0 : ret;

Wouldn't that cause the error from bio_align_to_lba() to be ignored
if bio->bi_vcnt is greater than 0?

That returns an error only if the alignment reduces the size to 0, so
there would be a bug somewhere if bi_vcnt is not also 0 in that case.

It would, but we wouldn't be seeing it as 'ret' would be obscured
if 'bio->bi_vcnt' continues to be greater than zero and 'ret' is set.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich