linux-kernel - Re: [REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing crash shortly after bootup

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Date:   Tue, 23 Feb 2021 07:21:34 +0000
From:   Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>
To:     Christoph Hellwig <hch@....de>
CC:     John Stultz <john.stultz@...aro.org>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Jens Axboe <axboe@...nel.dk>,
        David Anderson <dvander@...gle.com>,
        Alistair Delva <adelva@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Amit Pundir <amit.pundir@...aro.org>,
        YongQin Liu <yongqin.liu@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing
 crash shortly after bootup

On 2/22/21 23:10, Christoph Hellwig wrote:
> Well, that is a somewhat odd calling convention.  What about the patch below
> instead?  That being we really need to kill this bouncing code off..
If we can kill it off soon it will be great.
>
> diff --git a/block/bounce.c b/block/bounce.c
> index fc55314aa4269a..789fbcacb1e92a 100644
> --- a/block/bounce.c
> +++ b/block/bounce.c
> @@ -214,9 +214,9 @@ static void bounce_end_io_read_isa(struct bio *bio)
>  	__bounce_end_io_read(bio, &isa_page_pool);
>  }
>  
> -static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
> -		struct bio_set *bs)
> +static struct bio *bounce_clone_bio(struct bio *bio_src, bool passthrough)
>  {
> +	unsigned int nr_vecs = bio_segments(bio_src);
>  	struct bvec_iter iter;
>  	struct bio_vec bv;
>  	struct bio *bio;
> @@ -242,8 +242,10 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
>  	 *    asking for trouble and would force extra work on
>  	 *    __bio_clone_fast() anyways.
>  	 */
> -
> -	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
> +	if (passthrough)
> +		bio = bio_kmalloc(GFP_NOIO, nr_vecs);
> +	else
> +		bio = bio_alloc_bioset(GFP_NOIO, nr_vecs, &bounce_bio_set);
>  	if (!bio)
>  		return NULL;
>  	bio->bi_bdev		= bio_src->bi_bdev;
> @@ -269,11 +271,11 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
>  		break;
>  	}
>  
> -	if (bio_crypt_clone(bio, bio_src, gfp_mask) < 0)
> +	if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
>  		goto err_put;
>  
>  	if (bio_integrity(bio_src) &&
> -	    bio_integrity_clone(bio, bio_src, gfp_mask) < 0)
> +	    bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
>  		goto err_put;
>  
>  	bio_clone_blkg_association(bio, bio_src);
> @@ -313,8 +315,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
>  		submit_bio_noacct(*bio_orig);
>  		*bio_orig = bio;
>  	}
> -	bio = bounce_clone_bio(*bio_orig, GFP_NOIO, passthrough ? NULL :
> -			&bounce_bio_set);
> +	bio = bounce_clone_bio(*bio_orig, passthrough);
>  
>  	/*
>  	 * Bvec table can't be updated by bio_for_each_segment_all(),
>
Seems like this fixes the issue and does the cleanup in one patch, looks
good.