[RFC PATCH V1] raid5: Add R5_ReadNoMerge flag which prevent bio from merging at block layer

[RFC PATCH V1] raid5: Add R5_ReadNoMerge flag which prevent bio from merging at block layer

[majianpeng]

Because bios will merge at block-layer,so bios-error may caused by other
bio which be merged into to the same request.
Using this flag,it will find exactly error-sector and not do redundant
operation like re-write and re-read.

V0->V1:Using REQ_FLUSH instead REQ_NOMERGE avoid bio merging at block
layer.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
---
 drivers/md/raid5.c |   14 ++++++++++++--
 drivers/md/raid5.h |    1 +
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 04348d7..059989f6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -640,6 +640,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 			else
 				bi->bi_sector = (sh->sector
 						 + rdev->data_offset);
+			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
+				bi->bi_rw |= REQ_FLUSH;
+
 			bi->bi_flags = 1 << BIO_UPTODATE;
 			bi->bi_idx = 0;
 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
@@ -1739,7 +1742,9 @@ static void raid5_end_read_request(struct bio * bi, int error)
 			atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
 			clear_bit(R5_ReadError, &sh->dev[i].flags);
 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
-		}
+		} else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
+			clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
+
 		if (atomic_read(&rdev->read_errors))
 			atomic_set(&rdev->read_errors, 0);
 	} else {
@@ -1784,7 +1789,11 @@ static void raid5_end_read_request(struct bio * bi, int error)
 		else
 			retry = 1;
 		if (retry)
-			set_bit(R5_ReadError, &sh->dev[i].flags);
+			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags)) {
+				set_bit(R5_ReadError, &sh->dev[i].flags);
+				clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
+			} else
+				set_bit(R5_ReadNoMerge, &sh->dev[i].flags);
 		else {
 			clear_bit(R5_ReadError, &sh->dev[i].flags);
 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
@@ -4504,6 +4513,7 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
 			return handled;
 		}
 
+		set_bit(R5_ReadNoMerge, &sh->dev[dd_idx].flags);
 		handle_stripe(sh);
 		release_stripe(sh);
 		handled++;
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 2164021..6767d07 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -273,6 +273,7 @@ enum r5dev_flags {
 	R5_Wantwrite,
 	R5_Overlap,	/* There is a pending overlapping request
 			 * on this block */
+	R5_ReadNoMerge, /* prevent bio from merging in block-layer */
 	R5_ReadError,	/* seen a read error here recently */
 	R5_ReWrite,	/* have tried to over-write the readerror */
 
-- 
1.7.5.4

Re: [RFC PATCH V1] raid5: Add R5_ReadNoMerge flag which prevent bio from merging at block layer

[NeilBrown]

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On Fri, 13 Jul 2012 19:13:35 +0800 majianpeng <majianpeng@gmail.com> wrote:

> Because bios will merge at block-layer,so bios-error may caused by other
> bio which be merged into to the same request.
> Using this flag,it will find exactly error-sector and not do redundant
> operation like re-write and re-read.
> 
> V0->V1:Using REQ_FLUSH instead REQ_NOMERGE avoid bio merging at block
> layer.
> 
> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
> ---
>  drivers/md/raid5.c |   14 ++++++++++++--
>  drivers/md/raid5.h |    1 +
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 04348d7..059989f6 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -640,6 +640,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
>  			else
>  				bi->bi_sector = (sh->sector
>  						 + rdev->data_offset);
> +			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
> +				bi->bi_rw |= REQ_FLUSH;
> +
>  			bi->bi_flags = 1 << BIO_UPTODATE;
>  			bi->bi_idx = 0;
>  			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
> @@ -1739,7 +1742,9 @@ static void raid5_end_read_request(struct bio * bi, int error)
>  			atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
>  			clear_bit(R5_ReadError, &sh->dev[i].flags);
>  			clear_bit(R5_ReWrite, &sh->dev[i].flags);
> -		}
> +		} else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
> +			clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
> +
>  		if (atomic_read(&rdev->read_errors))
>  			atomic_set(&rdev->read_errors, 0);
>  	} else {
> @@ -1784,7 +1789,11 @@ static void raid5_end_read_request(struct bio * bi, int error)
>  		else
>  			retry = 1;
>  		if (retry)
> -			set_bit(R5_ReadError, &sh->dev[i].flags);
> +			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags)) {
> +				set_bit(R5_ReadError, &sh->dev[i].flags);
> +				clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
> +			} else
> +				set_bit(R5_ReadNoMerge, &sh->dev[i].flags);
>  		else {
>  			clear_bit(R5_ReadError, &sh->dev[i].flags);
>  			clear_bit(R5_ReWrite, &sh->dev[i].flags);
> @@ -4504,6 +4513,7 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
>  			return handled;
>  		}
>  
> +		set_bit(R5_ReadNoMerge, &sh->dev[dd_idx].flags);
>  		handle_stripe(sh);
>  		release_stripe(sh);
>  		handled++;
> diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
> index 2164021..6767d07 100644
> --- a/drivers/md/raid5.h
> +++ b/drivers/md/raid5.h
> @@ -273,6 +273,7 @@ enum r5dev_flags {
>  	R5_Wantwrite,
>  	R5_Overlap,	/* There is a pending overlapping request
>  			 * on this block */
> +	R5_ReadNoMerge, /* prevent bio from merging in block-layer */
>  	R5_ReadError,	/* seen a read error here recently */
>  	R5_ReWrite,	/* have tried to over-write the readerror */
>  


Thanks, I've applied this.

We should probably do a similar thing in fix_read_error and
fix_sync_read_error in RAID1 and RAID10...

Thanks,
NeilBrown


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Re: Re: [RFC PATCH V1] raid5: Add R5_ReadNoMerge flag which prevent bio from merging at block layer

[majianpeng]

On 2012-07-16 13:48 NeilBrown <neilb@suse.de> Wrote:
>On Fri, 13 Jul 2012 19:13:35 +0800 majianpeng <majianpeng@gmail.com> wrote:
>
>> Because bios will merge at block-layer,so bios-error may caused by other
>> bio which be merged into to the same request.
>> Using this flag,it will find exactly error-sector and not do redundant
>> operation like re-write and re-read.
>> 
>> V0->V1:Using REQ_FLUSH instead REQ_NOMERGE avoid bio merging at block
>> layer.
>> 
>> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
>> ---
>>  drivers/md/raid5.c |   14 ++++++++++++--
>>  drivers/md/raid5.h |    1 +
>>  2 files changed, 13 insertions(+), 2 deletions(-)
>> 
[snip]
>
>Thanks, I've applied this.
>
>We should probably do a similar thing in fix_read_error and
>fix_sync_read_error in RAID1 and RAID10...
>
Thanks, I'll do it.
>Thanks,
>NeilBrown
>
>

Re: Re: [RFC PATCH V1] raid5: Add R5_ReadNoMerge flag which prevent bio from merging at block layer

[majianpeng]

On 2012-07-16 13:48 NeilBrown <neilb@suse.de> Wrote:
>On Fri, 13 Jul 2012 19:13:35 +0800 majianpeng <majianpeng@gmail.com> wrote:
>
>> Because bios will merge at block-layer,so bios-error may caused by other
>> bio which be merged into to the same request.
>> Using this flag,it will find exactly error-sector and not do redundant
>> operation like re-write and re-read.
>> 
>> V0->V1:Using REQ_FLUSH instead REQ_NOMERGE avoid bio merging at block
>> layer.
>> 
>> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>

[snip]
>
>
>Thanks, I've applied this.
>
>We should probably do a similar thing in fix_read_error and
>fix_sync_read_error in RAID1 and RAID10...
>
I reviewed the code about fix_read_error/fix_sync_read_error.
It already do the similar thing.
>Thanks,
>NeilBrown
>
>