Patchwork [42/41,v2] dm: convey that all flushes are processed as empty

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Submitter Mike Snitzer
Date Sept. 8, 2010, 2:04 a.m.
Message ID <20100908020429.GA24635@redhat.com>
Download mbox | patch
Permalink /patch/64085/
State Not Applicable
Delegated to: David Miller
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Comments

Mike Snitzer - Sept. 8, 2010, 2:04 a.m.
Rename __clone_and_map_flush to __clone_and_map_empty_flush for added
clarity.

Simplify logic associated with REQ_FLUSH conditionals.

Introduce a BUG_ON() and add a few more helpful comments to the code
so that it is clear that all flushes are empty.

Cleanup __split_and_process_bio() so that an empty flush isn't processed
by a 'sector_count' focused while loop.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
 drivers/md/dm.c |   34 +++++++++++++++-------------------
 1 files changed, 15 insertions(+), 19 deletions(-)

Tejun, please feel free to fold this patch into (or insert after)
0025-dm-relax-ordering-of-bio-based-flush-implementation.patch

v2: Simplify logic associated with REQ_FLUSH conditionals

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Tejun Heo - Sept. 8, 2010, 4:09 p.m.
On 09/08/2010 04:04 AM, Mike Snitzer wrote:
> Rename __clone_and_map_flush to __clone_and_map_empty_flush for added
> clarity.
> 
> Simplify logic associated with REQ_FLUSH conditionals.
> 
> Introduce a BUG_ON() and add a few more helpful comments to the code
> so that it is clear that all flushes are empty.
> 
> Cleanup __split_and_process_bio() so that an empty flush isn't processed
> by a 'sector_count' focused while loop.
> 
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> ---
>  drivers/md/dm.c |   34 +++++++++++++++-------------------
>  1 files changed, 15 insertions(+), 19 deletions(-)
> 
> Tejun, please feel free to fold this patch into (or insert after)
> 0025-dm-relax-ordering-of-bio-based-flush-implementation.patch
> 
> v2: Simplify logic associated with REQ_FLUSH conditionals
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index cd2f7e7..f934e98 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -621,16 +621,17 @@ static void dec_pending(struct dm_io *io, int error)
>  		if (io_error == DM_ENDIO_REQUEUE)
>  			return;
>  
> -		if (!(bio->bi_rw & REQ_FLUSH) || !bio->bi_size) {
> -			trace_block_bio_complete(md->queue, bio);
> -			bio_endio(bio, io_error);
> -		} else {
> +		if ((bio->bi_rw & REQ_FLUSH) && bio->bi_size) {
>  			/*
>  			 * Preflush done for flush with data, reissue
>  			 * without REQ_FLUSH.
>  			 */
>  			bio->bi_rw &= ~REQ_FLUSH;
>  			queue_io(md, bio);
> +		} else {
> +			/* done with normal IO or empty flush */
> +			trace_block_bio_complete(md->queue, bio);
> +			bio_endio(bio, io_error);
>  		}
>  	}
>  }
> @@ -1132,16 +1133,15 @@ static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti,
>  		__issue_target_request(ci, ti, request_nr, len);
>  }
>  
> -static int __clone_and_map_flush(struct clone_info *ci)
> +static int __clone_and_map_empty_flush(struct clone_info *ci)
>  {
>  	unsigned target_nr = 0;
>  	struct dm_target *ti;
>  
> +	BUG_ON(bio_has_data(ci->bio));
>  	while ((ti = dm_table_get_target(ci->map, target_nr++)))
>  		__issue_target_requests(ci, ti, ti->num_flush_requests, 0);
>  
> -	ci->sector_count = 0;
> -
>  	return 0;
>  }
>  
> @@ -1282,7 +1282,6 @@ static int __clone_and_map(struct clone_info *ci)
>   */
>  static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
>  {
> -	bool is_flush = bio->bi_rw & REQ_FLUSH;
>  	struct clone_info ci;
>  	int error = 0;
>  
> @@ -1302,20 +1301,17 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
>  	ci.sector = bio->bi_sector;
>  	ci.idx = bio->bi_idx;
>  
> -	if (!is_flush) {
> +	start_io_acct(ci.io);
> +	if (bio->bi_rw & REQ_FLUSH) {
> +		ci.bio = &ci.md->flush_bio;
> +		ci.sector_count = 0;
> +		error = __clone_and_map_empty_flush(&ci);
> +		/* dec_pending submits any data associated with flush */
> +	} else {
>  		ci.bio = bio;
>  		ci.sector_count = bio_sectors(bio);
> -	} else {
> -		ci.bio = &ci.md->flush_bio;
> -		ci.sector_count = 1;
> -	}
> -
> -	start_io_acct(ci.io);
> -	while (ci.sector_count && !error) {
> -		if (!is_flush)
> +		while (ci.sector_count && !error)
>  			error = __clone_and_map(&ci);
> -		else
> -			error = __clone_and_map_flush(&ci);
>  	}
>  
>  	/* drop the extra reference count */
Tejun Heo - Sept. 8, 2010, 4:09 p.m.
On 09/08/2010 04:04 AM, Mike Snitzer wrote:
> Rename __clone_and_map_flush to __clone_and_map_empty_flush for added
> clarity.
> 
> Simplify logic associated with REQ_FLUSH conditionals.
> 
> Introduce a BUG_ON() and add a few more helpful comments to the code
> so that it is clear that all flushes are empty.
> 
> Cleanup __split_and_process_bio() so that an empty flush isn't processed
> by a 'sector_count' focused while loop.
> 
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> ---
>  drivers/md/dm.c |   34 +++++++++++++++-------------------
>  1 files changed, 15 insertions(+), 19 deletions(-)
> 
> Tejun, please feel free to fold this patch into (or insert after)
> 0025-dm-relax-ordering-of-bio-based-flush-implementation.patch

I added it after 26 and updated flush-fua branch accordingly.

Thank you.

Patch

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index cd2f7e7..f934e98 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -621,16 +621,17 @@  static void dec_pending(struct dm_io *io, int error)
 		if (io_error == DM_ENDIO_REQUEUE)
 			return;
 
-		if (!(bio->bi_rw & REQ_FLUSH) || !bio->bi_size) {
-			trace_block_bio_complete(md->queue, bio);
-			bio_endio(bio, io_error);
-		} else {
+		if ((bio->bi_rw & REQ_FLUSH) && bio->bi_size) {
 			/*
 			 * Preflush done for flush with data, reissue
 			 * without REQ_FLUSH.
 			 */
 			bio->bi_rw &= ~REQ_FLUSH;
 			queue_io(md, bio);
+		} else {
+			/* done with normal IO or empty flush */
+			trace_block_bio_complete(md->queue, bio);
+			bio_endio(bio, io_error);
 		}
 	}
 }
@@ -1132,16 +1133,15 @@  static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti,
 		__issue_target_request(ci, ti, request_nr, len);
 }
 
-static int __clone_and_map_flush(struct clone_info *ci)
+static int __clone_and_map_empty_flush(struct clone_info *ci)
 {
 	unsigned target_nr = 0;
 	struct dm_target *ti;
 
+	BUG_ON(bio_has_data(ci->bio));
 	while ((ti = dm_table_get_target(ci->map, target_nr++)))
 		__issue_target_requests(ci, ti, ti->num_flush_requests, 0);
 
-	ci->sector_count = 0;
-
 	return 0;
 }
 
@@ -1282,7 +1282,6 @@  static int __clone_and_map(struct clone_info *ci)
  */
 static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
 {
-	bool is_flush = bio->bi_rw & REQ_FLUSH;
 	struct clone_info ci;
 	int error = 0;
 
@@ -1302,20 +1301,17 @@  static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
 	ci.sector = bio->bi_sector;
 	ci.idx = bio->bi_idx;
 
-	if (!is_flush) {
+	start_io_acct(ci.io);
+	if (bio->bi_rw & REQ_FLUSH) {
+		ci.bio = &ci.md->flush_bio;
+		ci.sector_count = 0;
+		error = __clone_and_map_empty_flush(&ci);
+		/* dec_pending submits any data associated with flush */
+	} else {
 		ci.bio = bio;
 		ci.sector_count = bio_sectors(bio);
-	} else {
-		ci.bio = &ci.md->flush_bio;
-		ci.sector_count = 1;
-	}
-
-	start_io_acct(ci.io);
-	while (ci.sector_count && !error) {
-		if (!is_flush)
+		while (ci.sector_count && !error)
 			error = __clone_and_map(&ci);
-		else
-			error = __clone_and_map_flush(&ci);
 	}
 
 	/* drop the extra reference count */