[PATCH] md/raid10: fix FailFast test for wrong device

[PATCH] md/raid10: fix FailFast test for wrong device

[Guoqing Jiang]

We need to test FailFast flag for replacement device here
since the set up for writing is for the replacement, so we
need fix it like:

- if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
+ if (test_bit(FailFast, &conf->mirrors[d].replacement->flags))

Since commit f90145f317ef ("md/raid10: add rcu protection
to rdev access in raid10_sync_request.") had added the rcu
protection for the part, so let's extend the range protected
by rcu and use rdev directly.

Fixes: 1919cbb ("md/raid10: add failfast handling for writes.")
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
---
 drivers/md/raid10.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 3273887..f25a2ae 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3294,7 +3294,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			biolist = bio;
 			bio->bi_end_io = end_sync_read;
 			bio_set_op_attrs(bio, REQ_OP_READ, 0);
-			if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
+			if (test_bit(FailFast, &rdev->flags))
 				bio->bi_opf |= MD_FAILFAST;
 			bio->bi_iter.bi_sector = sector + rdev->data_offset;
 			bio->bi_bdev = rdev->bdev;
@@ -3306,7 +3306,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 				continue;
 			}
 			atomic_inc(&rdev->nr_pending);
-			rcu_read_unlock();
 
 			/* Need to set up for writing to the replacement */
 			bio = r10_bio->devs[i].repl_bio;
@@ -3317,11 +3316,12 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			biolist = bio;
 			bio->bi_end_io = end_sync_write;
 			bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
-			if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
+			if (test_bit(FailFast, &rdev->flags))
 				bio->bi_opf |= MD_FAILFAST;
 			bio->bi_iter.bi_sector = sector + rdev->data_offset;
 			bio->bi_bdev = rdev->bdev;
 			count++;
+			rcu_read_unlock();
 		}
 
 		if (count < 2) {
-- 
2.10.0

Re: [PATCH] md/raid10: fix FailFast test for wrong device

[Shaohua Li]

On Tue, Jun 13, 2017 at 11:16:08AM +0800, Guoqing Jiang wrote:
> We need to test FailFast flag for replacement device here
> since the set up for writing is for the replacement, so we
> need fix it like:
> 
> - if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
> + if (test_bit(FailFast, &conf->mirrors[d].replacement->flags))

good catch!
 
> Since commit f90145f317ef ("md/raid10: add rcu protection
> to rdev access in raid10_sync_request.") had added the rcu
> protection for the part, so let's extend the range protected
> by rcu and use rdev directly.

it's unnecessary, since we already increase the nr_pending for the rdev, but
this isn't harmful either.

Applied, thanks!
> Fixes: 1919cbb ("md/raid10: add failfast handling for writes.")
> Reviewed-by: NeilBrown <neilb@suse.com>
> Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
> ---
>  drivers/md/raid10.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 3273887..f25a2ae 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -3294,7 +3294,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>  			biolist = bio;
>  			bio->bi_end_io = end_sync_read;
>  			bio_set_op_attrs(bio, REQ_OP_READ, 0);
> -			if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
> +			if (test_bit(FailFast, &rdev->flags))
>  				bio->bi_opf |= MD_FAILFAST;
>  			bio->bi_iter.bi_sector = sector + rdev->data_offset;
>  			bio->bi_bdev = rdev->bdev;
> @@ -3306,7 +3306,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>  				continue;
>  			}
>  			atomic_inc(&rdev->nr_pending);
> -			rcu_read_unlock();
>  
>  			/* Need to set up for writing to the replacement */
>  			bio = r10_bio->devs[i].repl_bio;
> @@ -3317,11 +3316,12 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>  			biolist = bio;
>  			bio->bi_end_io = end_sync_write;
>  			bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
> -			if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
> +			if (test_bit(FailFast, &rdev->flags))
>  				bio->bi_opf |= MD_FAILFAST;
>  			bio->bi_iter.bi_sector = sector + rdev->data_offset;
>  			bio->bi_bdev = rdev->bdev;
>  			count++;
> +			rcu_read_unlock();
>  		}
>  
>  		if (count < 2) {
> -- 
> 2.10.0
> 
> --
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