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

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  [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast() NeilBrown <neilb@suse.com> - 2017-05-02 05:50 +0200
    Re: [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast() Christoph Hellwig <hch@infradead.org> - 2017-05-02 10:20 +0200
    Re: [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast() Javier González <jg@lightnvm.io> - 2017-05-02 13:30 +0200
      Re: [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast() NeilBrown <neilb@suse.com> - 2017-05-03 00:00 +0200
        Re: [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast() Javier González <jg@lightnvm.io> - 2017-05-03 08:50 +0200

#1634108 — [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast()

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,

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#1634227

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

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#1634350

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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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#1634639

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On Tue, May 02 2017, Javier González wrote:

>> 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.

Prior to my patchset, using bio_clone_bioset() wasn't wrong in drivers,
though it was a waste when bio_clone_fast() would to just as well as is
more efficient.
After my patchset, using it can be problematic.  I'm wondering what I
should do to encourage those problems to be more visible so that if
people to us it, they'll get a warning or something.

Thanks,
NeilBrown


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

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#1634773

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> On 2 May 2017, at 23.51, NeilBrown <neilb@suse.com> wrote:
> 
>> 
>> Hi Neil,
>> 
>> Looks good. Thanks for fixing this. I did not know that bio_clone_bioset
>> was not supposed to be used on drivers.
> 
> Prior to my patchset, using bio_clone_bioset() wasn't wrong in drivers,
> though it was a waste when bio_clone_fast() would to just as well as is
> more efficient.
> After my patchset, using it can be problematic.  I'm wondering what I
> should do to encourage those problems to be more visible so that if
> people to us it, they'll get a warning or something.
> 
> Thanks,
> NeilBrown
> 

Thanks for the explanation Neil. In my opinion a comment on top of
bio_clone_bioset() would be hellful, as Ming suggested. But a warning
might make sense too.

Javier

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