[dm-devel] [PATCH 1/2] dm thin metadata: Add support for a pre-commit callback

[Nikos Tsironis]

On 12/5/19 9:40 PM, Mike Snitzer wrote:
> On Wed, Dec 04 2019 at  9:07P -0500,
> Nikos Tsironis <ntsironis at arrikto.com> wrote:
> 
>> Add support for one pre-commit callback which is run right before the
>> metadata are committed.
>>
>> This allows the thin provisioning target to run a callback before the
>> metadata are committed and is required by the next commit.
>>
>> Cc: stable at vger.kernel.org
>> Signed-off-by: Nikos Tsironis <ntsironis at arrikto.com>
>> ---
>>   drivers/md/dm-thin-metadata.c | 29 +++++++++++++++++++++++++++++
>>   drivers/md/dm-thin-metadata.h |  7 +++++++
>>   2 files changed, 36 insertions(+)
>>
>> diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
>> index 4c68a7b93d5e..b88d6d701f5b 100644
>> --- a/drivers/md/dm-thin-metadata.c
>> +++ b/drivers/md/dm-thin-metadata.c
>> @@ -189,6 +189,15 @@ struct dm_pool_metadata {
>>   	sector_t data_block_size;
>>   
>>   	/*
>> +	 * Pre-commit callback.
>> +	 *
>> +	 * This allows the thin provisioning target to run a callback before
>> +	 * the metadata are committed.
>> +	 */
>> +	dm_pool_pre_commit_fn pre_commit_fn;
>> +	void *pre_commit_context;
>> +
>> +	/*
>>   	 * We reserve a section of the metadata for commit overhead.
>>   	 * All reported space does *not* include this.
>>   	 */
>> @@ -826,6 +835,14 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
>>   	if (unlikely(!pmd->in_service))
>>   		return 0;
>>   
>> +	if (pmd->pre_commit_fn) {
>> +		r = pmd->pre_commit_fn(pmd->pre_commit_context);
>> +		if (r < 0) {
>> +			DMERR("pre-commit callback failed");
>> +			return r;
>> +		}
>> +	}
>> +
>>   	r = __write_changed_details(pmd);
>>   	if (r < 0)
>>   		return r;
>> @@ -892,6 +909,8 @@ struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
>>   	pmd->in_service = false;
>>   	pmd->bdev = bdev;
>>   	pmd->data_block_size = data_block_size;
>> +	pmd->pre_commit_fn = NULL;
>> +	pmd->pre_commit_context = NULL;
>>   
>>   	r = __create_persistent_data_objects(pmd, format_device);
>>   	if (r) {
>> @@ -2044,6 +2063,16 @@ int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
>>   	return r;
>>   }
>>   
>> +void dm_pool_register_pre_commit_callback(struct dm_pool_metadata *pmd,
>> +					  dm_pool_pre_commit_fn fn,
>> +					  void *context)
>> +{
>> +	pmd_write_lock_in_core(pmd);
>> +	pmd->pre_commit_fn = fn;
>> +	pmd->pre_commit_context = context;
>> +	pmd_write_unlock(pmd);
>> +}
>> +
>>   int dm_pool_metadata_set_needs_check(struct dm_pool_metadata *pmd)
>>   {
>>   	int r = -EINVAL;
>> diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
>> index f6be0d733c20..7ef56bd2a7e3 100644
>> --- a/drivers/md/dm-thin-metadata.h
>> +++ b/drivers/md/dm-thin-metadata.h
>> @@ -230,6 +230,13 @@ bool dm_pool_metadata_needs_check(struct dm_pool_metadata *pmd);
>>    */
>>   void dm_pool_issue_prefetches(struct dm_pool_metadata *pmd);
>>   
>> +/* Pre-commit callback */
>> +typedef int (*dm_pool_pre_commit_fn)(void *context);
>> +
>> +void dm_pool_register_pre_commit_callback(struct dm_pool_metadata *pmd,
>> +					  dm_pool_pre_commit_fn fn,
>> +					  void *context);
>> +
>>   /*----------------------------------------------------------------*/
>>   
>>   #endif
>> -- 
>> 2.11.0
>>
> 
> I have this incremental, not seeing need to avoid using blkdev_issue_flush
>

Ack,

Nikos.
  
> ---
>   drivers/md/dm-thin.c | 12 +-----------
>   1 file changed, 1 insertion(+), 11 deletions(-)
> 
> diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
> index 9c9a323c0c30..255a52f7bbf0 100644
> --- a/drivers/md/dm-thin.c
> +++ b/drivers/md/dm-thin.c
> @@ -3203,18 +3203,8 @@ static void metadata_low_callback(void *context)
>   static int metadata_pre_commit_callback(void *context)
>   {
>   	struct pool_c *pt = context;
> -	struct bio bio;
> -	int r;
> -
> -	bio_init(&bio, NULL, 0);
> -	bio_set_dev(&bio, pt->data_dev->bdev);
> -	bio.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
> -
> -	r = submit_bio_wait(&bio);
>   
> -	bio_uninit(&bio);
> -
> -	return r;
> +	return blkdev_issue_flush(pt->data_dev->bdev, GFP_NOIO, NULL);
>   }
>   
>   static sector_t get_dev_size(struct block_device *bdev)
>