diff mbox series

[v4,11/13] blk-mq: Refactor and rename blk_mq_free_map_and_{requests->rqs}()

Message ID 1632472110-244938-12-git-send-email-john.garry@huawei.com (mailing list archive)
State New, archived
Headers show
Series blk-mq: Reduce static requests memory footprint for shared sbitmap | expand

Commit Message

John Garry Sept. 24, 2021, 8:28 a.m. UTC 
Refactor blk_mq_free_map_and_requests() such that it can be used at many
sites at which the tag map and rqs are freed.

Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the
alloc equivalent.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
 block/blk-mq-tag.c |  3 +--
 block/blk-mq.c     | 40 ++++++++++++++++++++++++----------------
 block/blk-mq.h     |  4 +++-
 3 files changed, 28 insertions(+), 19 deletions(-)

Comments

Ming Lei Sept. 26, 2021, 2:05 a.m. UTC | #1 
On Fri, Sep 24, 2021 at 04:28:28PM +0800, John Garry wrote:
> Refactor blk_mq_free_map_and_requests() such that it can be used at many
> sites at which the tag map and rqs are freed.
> 
> Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the
> alloc equivalent.
> 
> Suggested-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> ---
>  block/blk-mq-tag.c |  3 +--
>  block/blk-mq.c     | 40 ++++++++++++++++++++++++----------------
>  block/blk-mq.h     |  4 +++-
>  3 files changed, 28 insertions(+), 19 deletions(-)
> 
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index db99f1246795..a0ecc6d88f84 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -607,8 +607,7 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
>  		if (!new)
>  			return -ENOMEM;
>  
> -		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
> -		blk_mq_free_rq_map(*tagsptr, set->flags);
> +		blk_mq_free_map_and_rqs(set, *tagsptr, hctx->queue_num);
>  		*tagsptr = new;
>  	} else {
>  		/*
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 46772773b9c4..464ea20b9bcb 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2878,15 +2878,15 @@ static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
>  	return set->tags[hctx_idx];
>  }
>  
> -static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
> -					 unsigned int hctx_idx)
> +void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
> +			     struct blk_mq_tags *tags,
> +			     unsigned int hctx_idx)
>  {
>  	unsigned int flags = set->flags;
>  
> -	if (set->tags && set->tags[hctx_idx]) {
> -		blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
> -		blk_mq_free_rq_map(set->tags[hctx_idx], flags);
> -		set->tags[hctx_idx] = NULL;
> +	if (tags) {
> +		blk_mq_free_rqs(set, tags, hctx_idx);
> +		blk_mq_free_rq_map(tags, flags);
>  	}
>  }
>  
> @@ -2967,8 +2967,10 @@ static void blk_mq_map_swqueue(struct request_queue *q)
>  			 * fallback in case of a new remap fails
>  			 * allocation
>  			 */
> -			if (i && set->tags[i])
> -				blk_mq_free_map_and_requests(set, i);
> +			if (i && set->tags[i]) {
> +				blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +				set->tags[i] = NULL;
> +			}
>  
>  			hctx->tags = NULL;
>  			continue;
> @@ -3264,8 +3266,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
>  		struct blk_mq_hw_ctx *hctx = hctxs[j];
>  
>  		if (hctx) {
> -			if (hctx->tags)
> -				blk_mq_free_map_and_requests(set, j);
> +			blk_mq_free_map_and_rqs(set, set->tags[j], j);
> +			set->tags[j] = NULL;
>  			blk_mq_exit_hctx(q, set, hctx, j);
>  			hctxs[j] = NULL;
>  		}
> @@ -3361,8 +3363,10 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
>  	return 0;
>  
>  out_unwind:
> -	while (--i >= 0)
> -		blk_mq_free_map_and_requests(set, i);
> +	while (--i >= 0) {
> +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +		set->tags[i] = NULL;
> +	}
>  
>  	return -ENOMEM;
>  }
> @@ -3557,8 +3561,10 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
>  	return 0;
>  
>  out_free_mq_rq_maps:
> -	for (i = 0; i < set->nr_hw_queues; i++)
> -		blk_mq_free_map_and_requests(set, i);
> +	for (i = 0; i < set->nr_hw_queues; i++) {
> +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +		set->tags[i] = NULL;
> +	}
>  out_free_mq_map:
>  	for (i = 0; i < set->nr_maps; i++) {
>  		kfree(set->map[i].mq_map);
> @@ -3590,8 +3596,10 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
>  {
>  	int i, j;
>  
> -	for (i = 0; i < set->nr_hw_queues; i++)
> -		blk_mq_free_map_and_requests(set, i);
> +	for (i = 0; i < set->nr_hw_queues; i++) {
> +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +		set->tags[i] = NULL;
> +	}

There are 5 callers in which 'set->tags[i]' is cleared, so just
wondering why you don't clear set->tags[i] at default in
blk_mq_free_map_and_rqs(). And just call __blk_mq_free_map_and_rqs()
for the only other user?


Thanks,
Ming
John Garry Sept. 27, 2021, 9:02 a.m. UTC | #2 
On 26/09/2021 03:05, Ming Lei wrote:
> On Fri, Sep 24, 2021 at 04:28:28PM +0800, John Garry wrote:
>> Refactor blk_mq_free_map_and_requests() such that it can be used at many
>> sites at which the tag map and rqs are freed.
>>
>> Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the
>> alloc equivalent.
>>
>> Suggested-by: Ming Lei<ming.lei@redhat.com>
>> Signed-off-by: John Garry<john.garry@huawei.com>
>> Reviewed-by: Hannes Reinecke<hare@suse.de>
>> ---
>>   block/blk-mq-tag.c |  3 +--
>>   block/blk-mq.c     | 40 ++++++++++++++++++++++++----------------
>>   block/blk-mq.h     |  4 +++-
>>   3 files changed, 28 insertions(+), 19 deletions(-)
>>
>> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
>> index db99f1246795..a0ecc6d88f84 100644
>> --- a/block/blk-mq-tag.c
>> +++ b/block/blk-mq-tag.c
>> @@ -607,8 +607,7 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
>>   		if (!new)
>>   			return -ENOMEM;
>>   
>> -		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
>> -		blk_mq_free_rq_map(*tagsptr, set->flags);
>> +		blk_mq_free_map_and_rqs(set, *tagsptr, hctx->queue_num);
>>   		*tagsptr = new;
>>   	} else {
>>   		/*
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 46772773b9c4..464ea20b9bcb 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -2878,15 +2878,15 @@ static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
>>   	return set->tags[hctx_idx];
>>   }
>>   
>> -static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
>> -					 unsigned int hctx_idx)
>> +void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
>> +			     struct blk_mq_tags *tags,
>> +			     unsigned int hctx_idx)
>>   {
>>   	unsigned int flags = set->flags;
>>   
>> -	if (set->tags && set->tags[hctx_idx]) {
>> -		blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
>> -		blk_mq_free_rq_map(set->tags[hctx_idx], flags);
>> -		set->tags[hctx_idx] = NULL;
>> +	if (tags) {
>> +		blk_mq_free_rqs(set, tags, hctx_idx);
>> +		blk_mq_free_rq_map(tags, flags);
>>   	}
>>   }
>>   
>> @@ -2967,8 +2967,10 @@ static void blk_mq_map_swqueue(struct request_queue *q)
>>   			 * fallback in case of a new remap fails
>>   			 * allocation
>>   			 */
>> -			if (i && set->tags[i])
>> -				blk_mq_free_map_and_requests(set, i);
>> +			if (i && set->tags[i]) {
>> +				blk_mq_free_map_and_rqs(set, set->tags[i], i);
>> +				set->tags[i] = NULL;
>> +			}
>>   
>>   			hctx->tags = NULL;
>>   			continue;
>> @@ -3264,8 +3266,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
>>   		struct blk_mq_hw_ctx *hctx = hctxs[j];
>>   
>>   		if (hctx) {
>> -			if (hctx->tags)
>> -				blk_mq_free_map_and_requests(set, j);
>> +			blk_mq_free_map_and_rqs(set, set->tags[j], j);
>> +			set->tags[j] = NULL;
>>   			blk_mq_exit_hctx(q, set, hctx, j);
>>   			hctxs[j] = NULL;
>>   		}
>> @@ -3361,8 +3363,10 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
>>   	return 0;
>>   
>>   out_unwind:
>> -	while (--i >= 0)
>> -		blk_mq_free_map_and_requests(set, i);
>> +	while (--i >= 0) {
>> +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
>> +		set->tags[i] = NULL;
>> +	}
>>   
>>   	return -ENOMEM;
>>   }
>> @@ -3557,8 +3561,10 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
>>   	return 0;
>>   
>>   out_free_mq_rq_maps:
>> -	for (i = 0; i < set->nr_hw_queues; i++)
>> -		blk_mq_free_map_and_requests(set, i);
>> +	for (i = 0; i < set->nr_hw_queues; i++) {
>> +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
>> +		set->tags[i] = NULL;
>> +	}
>>   out_free_mq_map:
>>   	for (i = 0; i < set->nr_maps; i++) {
>>   		kfree(set->map[i].mq_map);
>> @@ -3590,8 +3596,10 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
>>   {
>>   	int i, j;
>>   
>> -	for (i = 0; i < set->nr_hw_queues; i++)
>> -		blk_mq_free_map_and_requests(set, i);
>> +	for (i = 0; i < set->nr_hw_queues; i++) {
>> +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
>> +		set->tags[i] = NULL;
>> +	}
> There are 5 callers in which 'set->tags[i]' is cleared, so just
> wondering why you don't clear set->tags[i] at default in
> blk_mq_free_map_and_rqs(). And just call __blk_mq_free_map_and_rqs()
> for the only other user?

blk_mq_free_map_and_rqs() is not always passed set->tags[i]:

- blk_mq_tag_update_depth() calls blk_mq_free_map_and_rqs() for sched tags

- __blk_mq_alloc_rq_maps() calls blk_mq_free_map_and_rqs() for 
shared_sbitmap_tags

Function __blk_mq_free_map_and_rqs() is not public and really only 
intended for set->tags[i]

So I did consider passing the address of the tags pointer to
blk_mq_free_map_and_rqs(), like:

void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
			struct blk_mq_tag **tags,
			unsigned int hctx_idx)

{
	...
	*tags = NULL;
}

But then the API becomes a bit asymmetric, as we deal with tags pointer 
normally:

struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
					     unsigned int hctx_idx,
					     unsigned int depth);


However, apart from this, I can change __blk_mq_free_map_and_rqs() to 
NULLify set->tags[i], as it is always passed set->tags[i].

Do you have a preference?

Thanks,
John
Ming Lei Sept. 27, 2021, 9:19 a.m. UTC | #3 
On Mon, Sep 27, 2021 at 10:02:40AM +0100, John Garry wrote:
> On 26/09/2021 03:05, Ming Lei wrote:
> > On Fri, Sep 24, 2021 at 04:28:28PM +0800, John Garry wrote:
> > > Refactor blk_mq_free_map_and_requests() such that it can be used at many
> > > sites at which the tag map and rqs are freed.
> > > 
> > > Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the
> > > alloc equivalent.
> > > 
> > > Suggested-by: Ming Lei<ming.lei@redhat.com>
> > > Signed-off-by: John Garry<john.garry@huawei.com>
> > > Reviewed-by: Hannes Reinecke<hare@suse.de>
> > > ---
> > >   block/blk-mq-tag.c |  3 +--
> > >   block/blk-mq.c     | 40 ++++++++++++++++++++++++----------------
> > >   block/blk-mq.h     |  4 +++-
> > >   3 files changed, 28 insertions(+), 19 deletions(-)
> > > 
> > > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> > > index db99f1246795..a0ecc6d88f84 100644
> > > --- a/block/blk-mq-tag.c
> > > +++ b/block/blk-mq-tag.c
> > > @@ -607,8 +607,7 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
> > >   		if (!new)
> > >   			return -ENOMEM;
> > > -		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
> > > -		blk_mq_free_rq_map(*tagsptr, set->flags);
> > > +		blk_mq_free_map_and_rqs(set, *tagsptr, hctx->queue_num);
> > >   		*tagsptr = new;
> > >   	} else {
> > >   		/*
> > > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > > index 46772773b9c4..464ea20b9bcb 100644
> > > --- a/block/blk-mq.c
> > > +++ b/block/blk-mq.c
> > > @@ -2878,15 +2878,15 @@ static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
> > >   	return set->tags[hctx_idx];
> > >   }
> > > -static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
> > > -					 unsigned int hctx_idx)
> > > +void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
> > > +			     struct blk_mq_tags *tags,
> > > +			     unsigned int hctx_idx)
> > >   {
> > >   	unsigned int flags = set->flags;
> > > -	if (set->tags && set->tags[hctx_idx]) {
> > > -		blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
> > > -		blk_mq_free_rq_map(set->tags[hctx_idx], flags);
> > > -		set->tags[hctx_idx] = NULL;
> > > +	if (tags) {
> > > +		blk_mq_free_rqs(set, tags, hctx_idx);
> > > +		blk_mq_free_rq_map(tags, flags);
> > >   	}
> > >   }
> > > @@ -2967,8 +2967,10 @@ static void blk_mq_map_swqueue(struct request_queue *q)
> > >   			 * fallback in case of a new remap fails
> > >   			 * allocation
> > >   			 */
> > > -			if (i && set->tags[i])
> > > -				blk_mq_free_map_and_requests(set, i);
> > > +			if (i && set->tags[i]) {
> > > +				blk_mq_free_map_and_rqs(set, set->tags[i], i);
> > > +				set->tags[i] = NULL;
> > > +			}
> > >   			hctx->tags = NULL;
> > >   			continue;
> > > @@ -3264,8 +3266,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
> > >   		struct blk_mq_hw_ctx *hctx = hctxs[j];
> > >   		if (hctx) {
> > > -			if (hctx->tags)
> > > -				blk_mq_free_map_and_requests(set, j);
> > > +			blk_mq_free_map_and_rqs(set, set->tags[j], j);
> > > +			set->tags[j] = NULL;
> > >   			blk_mq_exit_hctx(q, set, hctx, j);
> > >   			hctxs[j] = NULL;
> > >   		}
> > > @@ -3361,8 +3363,10 @@ static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
> > >   	return 0;
> > >   out_unwind:
> > > -	while (--i >= 0)
> > > -		blk_mq_free_map_and_requests(set, i);
> > > +	while (--i >= 0) {
> > > +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> > > +		set->tags[i] = NULL;
> > > +	}
> > >   	return -ENOMEM;
> > >   }
> > > @@ -3557,8 +3561,10 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
> > >   	return 0;
> > >   out_free_mq_rq_maps:
> > > -	for (i = 0; i < set->nr_hw_queues; i++)
> > > -		blk_mq_free_map_and_requests(set, i);
> > > +	for (i = 0; i < set->nr_hw_queues; i++) {
> > > +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> > > +		set->tags[i] = NULL;
> > > +	}
> > >   out_free_mq_map:
> > >   	for (i = 0; i < set->nr_maps; i++) {
> > >   		kfree(set->map[i].mq_map);
> > > @@ -3590,8 +3596,10 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
> > >   {
> > >   	int i, j;
> > > -	for (i = 0; i < set->nr_hw_queues; i++)
> > > -		blk_mq_free_map_and_requests(set, i);
> > > +	for (i = 0; i < set->nr_hw_queues; i++) {
> > > +		blk_mq_free_map_and_rqs(set, set->tags[i], i);
> > > +		set->tags[i] = NULL;
> > > +	}
> > There are 5 callers in which 'set->tags[i]' is cleared, so just
> > wondering why you don't clear set->tags[i] at default in
> > blk_mq_free_map_and_rqs(). And just call __blk_mq_free_map_and_rqs()
> > for the only other user?
> 
> blk_mq_free_map_and_rqs() is not always passed set->tags[i]:
> 
> - blk_mq_tag_update_depth() calls blk_mq_free_map_and_rqs() for sched tags
> 
> - __blk_mq_alloc_rq_maps() calls blk_mq_free_map_and_rqs() for
> shared_sbitmap_tags
> 
> Function __blk_mq_free_map_and_rqs() is not public and really only intended
> for set->tags[i]
> 
> So I did consider passing the address of the tags pointer to
> blk_mq_free_map_and_rqs(), like:
> 
> void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
> 			struct blk_mq_tag **tags,
> 			unsigned int hctx_idx)
> 
> {
> 	...
> 	*tags = NULL;
> }
> 
> But then the API becomes a bit asymmetric, as we deal with tags pointer
> normally:
> 
> struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
> 					     unsigned int hctx_idx,
> 					     unsigned int depth);
> 
> 
> However, apart from this, I can change __blk_mq_free_map_and_rqs() to
> NULLify set->tags[i], as it is always passed set->tags[i].
> 
> Do you have a preference?

I meant there are 5 following uses in your patch:

+                               blk_mq_free_map_and_rqs(set, set->tags[i], i);
+                               set->tags[i] = NULL;

and one new helper(blk_mq_free_set_map_and_rqs(set, i)?) can be added for just
doing that, 

Thanks,
Ming
John Garry Sept. 27, 2021, 9:40 a.m. UTC | #4 
On 27/09/2021 10:19, Ming Lei wrote:
>> However, apart from this, I can change __blk_mq_free_map_and_rqs() to
>> NULLify set->tags[i], as it is always passed set->tags[i].
>>
>> Do you have a preference?
> I meant there are 5 following uses in your patch:
> 
> +                               blk_mq_free_map_and_rqs(set, set->tags[i], i);
> +                               set->tags[i] = NULL;
> 
> and one new helper(blk_mq_free_set_map_and_rqs(set, i)?) can be added for just
> doing that,

Ah, ok, but in the next patch we replace these blk_mq_free_map_and_rqs() 
calls with __blk_mq_free_map_and_rqs(), and __blk_mq_free_map_and_rqs() 
is always passed set->tags[i], so we do as you request there, i.e. 
NULLify set->tags[i] in __blk_mq_free_map_and_rqs().

Thanks,
John
diff mbox series

Patch

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index db99f1246795..a0ecc6d88f84 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -607,8 +607,7 @@  int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 		if (!new)
 			return -ENOMEM;
 
-		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
-		blk_mq_free_rq_map(*tagsptr, set->flags);
+		blk_mq_free_map_and_rqs(set, *tagsptr, hctx->queue_num);
 		*tagsptr = new;
 	} else {
 		/*
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 46772773b9c4..464ea20b9bcb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2878,15 +2878,15 @@  static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 	return set->tags[hctx_idx];
 }
 
-static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
-					 unsigned int hctx_idx)
+void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
+			     struct blk_mq_tags *tags,
+			     unsigned int hctx_idx)
 {
 	unsigned int flags = set->flags;
 
-	if (set->tags && set->tags[hctx_idx]) {
-		blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
-		blk_mq_free_rq_map(set->tags[hctx_idx], flags);
-		set->tags[hctx_idx] = NULL;
+	if (tags) {
+		blk_mq_free_rqs(set, tags, hctx_idx);
+		blk_mq_free_rq_map(tags, flags);
 	}
 }
 
@@ -2967,8 +2967,10 @@  static void blk_mq_map_swqueue(struct request_queue *q)
 			 * fallback in case of a new remap fails
 			 * allocation
 			 */
-			if (i && set->tags[i])
-				blk_mq_free_map_and_requests(set, i);
+			if (i && set->tags[i]) {
+				blk_mq_free_map_and_rqs(set, set->tags[i], i);
+				set->tags[i] = NULL;
+			}
 
 			hctx->tags = NULL;
 			continue;
@@ -3264,8 +3266,8 @@  static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 		struct blk_mq_hw_ctx *hctx = hctxs[j];
 
 		if (hctx) {
-			if (hctx->tags)
-				blk_mq_free_map_and_requests(set, j);
+			blk_mq_free_map_and_rqs(set, set->tags[j], j);
+			set->tags[j] = NULL;
 			blk_mq_exit_hctx(q, set, hctx, j);
 			hctxs[j] = NULL;
 		}
@@ -3361,8 +3363,10 @@  static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 	return 0;
 
 out_unwind:
-	while (--i >= 0)
-		blk_mq_free_map_and_requests(set, i);
+	while (--i >= 0) {
+		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		set->tags[i] = NULL;
+	}
 
 	return -ENOMEM;
 }
@@ -3557,8 +3561,10 @@  int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 	return 0;
 
 out_free_mq_rq_maps:
-	for (i = 0; i < set->nr_hw_queues; i++)
-		blk_mq_free_map_and_requests(set, i);
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		set->tags[i] = NULL;
+	}
 out_free_mq_map:
 	for (i = 0; i < set->nr_maps; i++) {
 		kfree(set->map[i].mq_map);
@@ -3590,8 +3596,10 @@  void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
 {
 	int i, j;
 
-	for (i = 0; i < set->nr_hw_queues; i++)
-		blk_mq_free_map_and_requests(set, i);
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		blk_mq_free_map_and_rqs(set, set->tags[i], i);
+		set->tags[i] = NULL;
+	}
 
 	if (blk_mq_is_sbitmap_shared(set->flags))
 		blk_mq_exit_shared_sbitmap(set);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 83585a344568..bcb0ca89d37a 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -57,7 +57,9 @@  void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags);
 struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
 				unsigned int hctx_idx, unsigned int depth);
-
+void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
+			     struct blk_mq_tags *tags,
+			     unsigned int hctx_idx);
 /*
  * Internal helpers for request insertion into sw queues
  */