Re: [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast()

From: "Javier González" <jg@lightnvm.io>
To: NeilBrown <neilb@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Ming Lei <tom.leiming@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast()
Date: Tue, 2 May 2017 13:22:54 +0200	[thread overview]
Message-ID: <FC7673E1-94A3-4C93-960F-EF05A0BF09B0@lightnvm.io> (raw)
In-Reply-To: <149369654558.5146.13818001419050826182.stgit@noble>

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> On 2 May 2017, at 05.42, NeilBrown <neilb@suse.com> wrote:
> 
> pblk_submit_read() uses bio_clone_bioset() but doesn't change the
> io_vec, so bio_clone_fast() is a better choice.
> 
> It also uses fs_bio_set which is intended for filesystems.  Using it
> in a device driver can deadlock.
> So allocate a new bioset, and and use bio_clone_fast().
> 
> Signed-off-by: NeilBrown <neilb@suse.com>
> ---
> drivers/lightnvm/pblk-init.c |   12 +++++++++++-
> drivers/lightnvm/pblk-read.c |    2 +-
> drivers/lightnvm/pblk.h      |    1 +
> 3 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
> index b3fec8ec55b8..aaefbccce30e 100644
> --- a/drivers/lightnvm/pblk-init.c
> +++ b/drivers/lightnvm/pblk-init.c
> @@ -23,6 +23,7 @@
> static struct kmem_cache *pblk_blk_ws_cache, *pblk_rec_cache, *pblk_r_rq_cache,
> 					*pblk_w_rq_cache, *pblk_line_meta_cache;
> static DECLARE_RWSEM(pblk_lock);
> +struct bio_set *pblk_bio_set;
> 
> static int pblk_rw_io(struct request_queue *q, struct pblk *pblk,
> 			  struct bio *bio)
> @@ -946,11 +947,20 @@ static struct nvm_tgt_type tt_pblk = {
> 
> static int __init pblk_module_init(void)
> {
> -	return nvm_register_tgt_type(&tt_pblk);
> +	int ret;
> +
> +	pblk_bio_set = bioset_create(BIO_POOL_SIZE, 0, 0);
> +	if (!pblk_bio_set)
> +		return -ENOMEM;
> +	ret = nvm_register_tgt_type(&tt_pblk);
> +	if (ret)
> +		bioset_free(pblk_bio_set);
> +	return ret;
> }
> 
> static void pblk_module_exit(void)
> {
> +	bioset_free(pblk_bio_set);
> 	nvm_unregister_tgt_type(&tt_pblk);
> }
> 
> diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
> index 4a12f14d78c6..8ee0c50a7a71 100644
> --- a/drivers/lightnvm/pblk-read.c
> +++ b/drivers/lightnvm/pblk-read.c
> @@ -342,7 +342,7 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
> 		struct pblk_r_ctx *r_ctx = nvm_rq_to_pdu(rqd);
> 
> 		/* Clone read bio to deal with read errors internally */
> -		int_bio = bio_clone_bioset(bio, GFP_KERNEL, fs_bio_set);
> +		int_bio = bio_clone_fast(bio, GFP_KERNEL, pblk_bio_set);
> 		if (!int_bio) {
> 			pr_err("pblk: could not clone read bio\n");
> 			return NVM_IO_ERR;
> diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
> index 99f3186b5288..95b665f23925 100644
> --- a/drivers/lightnvm/pblk.h
> +++ b/drivers/lightnvm/pblk.h
> @@ -702,6 +702,7 @@ void pblk_write_should_kick(struct pblk *pblk);
> /*
>  * pblk read path
>  */
> +extern struct bio_set *pblk_bio_set;
> int pblk_submit_read(struct pblk *pblk, struct bio *bio);
> int pblk_submit_read_gc(struct pblk *pblk, u64 *lba_list, void *data,
> 			unsigned int nr_secs, unsigned int *secs_to_gc,

Hi Neil,

Looks good. Thanks for fixing this. I did not know that bio_clone_bioset
was not supposed to be used on drivers.

Reviewed-by: Javier González <javier@cnexlabs.com>
Tested-by: Javier González <javier@cnexlabs.com>

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