[07/10] block: kill merge_bvec_fn() completely
diff mbox

Message ID 5547241B.1040903@kernel.org
State New
Headers show

Commit Message

Lin Ming May 4, 2015, 7:47 a.m. UTC
On 04/28/2015 03:09 PM, NeilBrown wrote:
> On Mon, 27 Apr 2015 23:48:34 -0700 Ming Lin <mlin@kernel.org> wrote:
> 
>> From: Kent Overstreet <kent.overstreet@gmail.com>
>>
>> As generic_make_request() is now able to handle arbitrarily sized bios,
>> it's no longer necessary for each individual block driver to define its
>> own ->merge_bvec_fn() callback. Remove every invocation completely.
> 
> This patch it just a little premature I think.
> 
> md/raid5 still assumes read requests will mostly fit within a single chunk
> (which merge_bvec_fn encourages) so they can be serviced without using the
> stripe-cache.
> You've just broken that assumption.
> 
> I think 'chunk_aligned_read' needs to get a loop using bio_split, a bit like
> raid0, first.

How about below?

 drivers/md/raid5.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

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Comments

Lin Ming May 6, 2015, 7:10 a.m. UTC | #1
On Mon, May 4, 2015 at 12:47 AM, Ming Lin <mlin@kernel.org> wrote:
> On 04/28/2015 03:09 PM, NeilBrown wrote:
>> On Mon, 27 Apr 2015 23:48:34 -0700 Ming Lin <mlin@kernel.org> wrote:
>>
>>> From: Kent Overstreet <kent.overstreet@gmail.com>
>>>
>>> As generic_make_request() is now able to handle arbitrarily sized bios,
>>> it's no longer necessary for each individual block driver to define its
>>> own ->merge_bvec_fn() callback. Remove every invocation completely.
>>
>> This patch it just a little premature I think.
>>
>> md/raid5 still assumes read requests will mostly fit within a single chunk
>> (which merge_bvec_fn encourages) so they can be serviced without using the
>> stripe-cache.
>> You've just broken that assumption.
>>
>> I think 'chunk_aligned_read' needs to get a loop using bio_split, a bit like
>> raid0, first.
>
> How about below?

Hi NeilBrown,

Are you OK with below fix?
Then I'll include it in the next version.

Thanks.

>
>  drivers/md/raid5.c | 35 ++++++++++++++++++++++++++++++++---
>  1 file changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index e42b624..2ddfa1e 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -4709,7 +4709,7 @@ static void raid5_align_endio(struct bio *bi, int error)
>         add_bio_to_retry(raid_bi, conf);
>  }
>
> -static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
> +static int __chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
>  {
>         struct r5conf *conf = mddev->private;
>         int dd_idx;
> @@ -4718,7 +4718,7 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
>         sector_t end_sector;
>
>         if (!in_chunk_boundary(mddev, raid_bio)) {
> -               pr_debug("chunk_aligned_read : non aligned\n");
> +               pr_debug("__chunk_aligned_read : non aligned\n");
>                 return 0;
>         }
>         /*
> @@ -4793,6 +4793,35 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
>         }
>  }
>
> +static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
> +{
> +       struct bio *split;
> +
> +       do {
> +               sector_t sector = raid_bio->bi_iter.bi_sector;
> +               unsigned chunk_sects = mddev->chunk_sectors;
> +
> +               unsigned sectors = chunk_sects -
> +                       (likely(is_power_of_2(chunk_sects))
> +                        ? (sector & (chunk_sects-1))
> +                        : sector_div(sector, chunk_sects));
> +
> +               if (sectors < bio_sectors(raid_bio)) {
> +                       split = bio_split(raid_bio, sectors, GFP_NOIO, fs_bio_set);
> +                       bio_chain(split, raid_bio);
> +               } else
> +                       split = raid_bio;
> +
> +               if (!__chunk_aligned_read(mddev, split)) {
> +                       if (split != raid_bio)
> +                               generic_make_request(raid_bio);
> +                       return split;
> +               }
> +       } while (split != raid_bio);
> +
> +       return NULL;
> +}
> +
>  /* __get_priority_stripe - get the next stripe to process
>   *
>   * Full stripe writes are allowed to pass preread active stripes up until
> @@ -5071,7 +5100,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
>          */
>         if (rw == READ && mddev->degraded == 0 &&
>              mddev->reshape_position == MaxSector &&
> -            chunk_aligned_read(mddev,bi))
> +            (!(bi = chunk_aligned_read(mddev, bi))))
>                 return;
>
>         if (unlikely(bi->bi_rw & REQ_DISCARD)) {
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Christoph Hellwig May 6, 2015, 7:26 a.m. UTC | #2
> -static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
> +static int __chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)

Call it raid5_read_one_chunk or something similar descriptive?

>  {
>  	struct r5conf *conf = mddev->private;
>  	int dd_idx;
> @@ -4718,7 +4718,7 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
>  	sector_t end_sector;
>  
>  	if (!in_chunk_boundary(mddev, raid_bio)) {
> -		pr_debug("chunk_aligned_read : non aligned\n");
> +		pr_debug("__chunk_aligned_read : non aligned\n");

Switch to __func__?

> +static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
> +{
> +	struct bio *split;
> +
> +	do {
> +		sector_t sector = raid_bio->bi_iter.bi_sector;
> +		unsigned chunk_sects = mddev->chunk_sectors;
> +
> +		unsigned sectors = chunk_sects -
> +			(likely(is_power_of_2(chunk_sects))
> +			 ? (sector & (chunk_sects-1))
> +			 : sector_div(sector, chunk_sects));

This would be a lot more readable with a good old if.

>  	if (rw == READ && mddev->degraded == 0 &&
>  	     mddev->reshape_position == MaxSector &&
> -	     chunk_aligned_read(mddev,bi))
> +	     (!(bi = chunk_aligned_read(mddev, bi))))
>  		return;

	if (rw == READ && mddev->degraded == 0 &&
	    mddev->reshape_position == MaxSector) {
		bi = chunk_aligned_read(mddev, bi);
		if (!bi)
			return;
	}
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Lin Ming May 6, 2015, 5:05 p.m. UTC | #3
On Wed, May 6, 2015 at 12:26 AM, Christoph Hellwig <hch@lst.de> wrote:
>> -static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
>> +static int __chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
>
> Call it raid5_read_one_chunk or something similar descriptive?
>
>>  {
>>       struct r5conf *conf = mddev->private;
>>       int dd_idx;
>> @@ -4718,7 +4718,7 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
>>       sector_t end_sector;
>>
>>       if (!in_chunk_boundary(mddev, raid_bio)) {
>> -             pr_debug("chunk_aligned_read : non aligned\n");
>> +             pr_debug("__chunk_aligned_read : non aligned\n");
>
> Switch to __func__?
>
>> +static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
>> +{
>> +     struct bio *split;
>> +
>> +     do {
>> +             sector_t sector = raid_bio->bi_iter.bi_sector;
>> +             unsigned chunk_sects = mddev->chunk_sectors;
>> +
>> +             unsigned sectors = chunk_sects -
>> +                     (likely(is_power_of_2(chunk_sects))
>> +                      ? (sector & (chunk_sects-1))
>> +                      : sector_div(sector, chunk_sects));
>
> This would be a lot more readable with a good old if.
>
>>       if (rw == READ && mddev->degraded == 0 &&
>>            mddev->reshape_position == MaxSector &&
>> -          chunk_aligned_read(mddev,bi))
>> +          (!(bi = chunk_aligned_read(mddev, bi))))
>>               return;
>
>         if (rw == READ && mddev->degraded == 0 &&
>             mddev->reshape_position == MaxSector) {
>                 bi = chunk_aligned_read(mddev, bi);
>                 if (!bi)
>                         return;
>         }

Will update all. Thanks.
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Patch
diff mbox

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e42b624..2ddfa1e 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4709,7 +4709,7 @@  static void raid5_align_endio(struct bio *bi, int error)
 	add_bio_to_retry(raid_bi, conf);
 }
 
-static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
+static int __chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
 {
 	struct r5conf *conf = mddev->private;
 	int dd_idx;
@@ -4718,7 +4718,7 @@  static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
 	sector_t end_sector;
 
 	if (!in_chunk_boundary(mddev, raid_bio)) {
-		pr_debug("chunk_aligned_read : non aligned\n");
+		pr_debug("__chunk_aligned_read : non aligned\n");
 		return 0;
 	}
 	/*
@@ -4793,6 +4793,35 @@  static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
 	}
 }
 
+static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
+{
+	struct bio *split;
+
+	do {
+		sector_t sector = raid_bio->bi_iter.bi_sector;
+		unsigned chunk_sects = mddev->chunk_sectors;
+
+		unsigned sectors = chunk_sects -
+			(likely(is_power_of_2(chunk_sects))
+			 ? (sector & (chunk_sects-1))
+			 : sector_div(sector, chunk_sects));
+
+		if (sectors < bio_sectors(raid_bio)) {
+			split = bio_split(raid_bio, sectors, GFP_NOIO, fs_bio_set);
+			bio_chain(split, raid_bio);
+		} else
+			split = raid_bio;
+
+		if (!__chunk_aligned_read(mddev, split)) {
+			if (split != raid_bio)
+				generic_make_request(raid_bio);
+			return split;
+		}
+	} while (split != raid_bio);
+
+	return NULL;
+}
+
 /* __get_priority_stripe - get the next stripe to process
  *
  * Full stripe writes are allowed to pass preread active stripes up until
@@ -5071,7 +5100,7 @@  static void make_request(struct mddev *mddev, struct bio * bi)
 	 */
 	if (rw == READ && mddev->degraded == 0 &&
 	     mddev->reshape_position == MaxSector &&
-	     chunk_aligned_read(mddev,bi))
+	     (!(bi = chunk_aligned_read(mddev, bi))))
 		return;
 
 	if (unlikely(bi->bi_rw & REQ_DISCARD)) {