On Fri, 13 Jul 2012 19:13:35 +0800 majianpeng <majianpeng@xxxxxxxxx> 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@xxxxxxxxx>
> ---
> 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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