Re: [PATCH 8/8] block: stop calling blk_queue_bounce for passthrough requests

[Christoph Hellwig <hch@lst.de>]

On Thu, Apr 08, 2021 at 02:45:06PM -0700, Guenter Roeck wrote:
> On Wed, Mar 31, 2021 at 09:30:01AM +0200, Christoph Hellwig wrote:
> > Instead of overloading the passthrough fast path with the deprecated
> > block layer bounce buffering let the users that combine an old
> > undermaintained driver with a highmem system pay the price by always
> > falling back to copies in that case.
> > 
> 
> Hmm, that price is pretty high. When trying to boot sh images from usb,
> it results in a traceback, followed by an i/o error, and the drive
> fails to open.

That's just because this warning is completely bogus, sorry.

Does this patch fix the boot for you?

diff --git a/block/blk-map.c b/block/blk-map.c
index dac78376acc899..3743158ddaeb76 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -485,9 +485,6 @@ int blk_rq_append_bio(struct request *rq, struct bio *bio)
 	struct bio_vec bv;
 	unsigned int nr_segs = 0;
 
-	if (WARN_ON_ONCE(rq->q->limits.bounce != BLK_BOUNCE_NONE))
-		return -EINVAL;
-
 	bio_for_each_bvec(bv, bio, iter)
 		nr_segs++;