On Mon, Nov 18, 2024 at 7:44 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > > From: Yu Kuai <yukuai3@xxxxxxxxxx> > > There are two BUG reports that raid5 will hang at > bitmap_startwrite([1],[2]), root cause is that bitmap start write and end > write is unbalanced, and while reviewing raid5 code, it's found that Hi Kuai It's better to describe more about "unbalanced" in the patch. For raid5, bitmap is set and cleared based on stripe->dev[] now. It looks like the set operation matches the clear operation already. > bitmap operations can be optimized. For example, for a 4 disks raid5, with > chunksize=8k, if user issue a IO (0 + 48k) to the array: > > ┌────────────────────────────────────────────────────────────┐ > │chunk 0 │ > │ ┌────────────┬─────────────┬─────────────┬────────────┼ > │ sh0 │A0: 0 + 4k │A1: 8k + 4k │A2: 16k + 4k │A3: P │ > │ ┼────────────┼─────────────┼─────────────┼────────────┼ > │ sh1 │B0: 4k + 4k │B1: 12k + 4k │B2: 20k + 4k │B3: P │ > ┼──────┴────────────┴─────────────┴─────────────┴────────────┼ > │chunk 1 │ > │ ┌────────────┬─────────────┬─────────────┬────────────┤ > │ sh2 │C0: 24k + 4k│C1: 32k + 4k │C2: P │C3: 40k + 4k│ > │ ┼────────────┼─────────────┼─────────────┼────────────┼ > │ sh3 │D0: 28k + 4k│D1: 36k + 4k │D2: P │D3: 44k + 4k│ > └──────┴────────────┴─────────────┴─────────────┴────────────┘ > > Before this patch, 4 stripe head will be used, and each sh will attach > bio for 3 disks, and each attached bio will trigger > bitmap_startwrite() once, which means total 12 times. > - 3 times (0 + 4k), for (A0, A1 and A2) > - 3 times (4 + 4k), for (B0, B1 and B2) > - 3 times (8 + 4k), for (C0, C1 and C3) > - 3 times (12 + 4k), for (D0, D1 and D3) > > After this patch, md upper layer will calculate that IO range (0 + 48k) > is corresponding to the bitmap (0 + 16k), and call bitmap_startwrite() > just once. > > Noted that this patch will align bitmap ranges to the chunks, for example, > if user issue a IO (0 + 4k) to array: > > - Before this patch, 1 time (0 + 4k), for A0; > - After this patch, 1 time (0 + 8k) for chunk 0; > > Usually, one bitmap bit will represent more than one disk chunk, and this > doesn't have any difference. And even if user really created a array > that one chunk contain multiple bits, the overhead is that more data > will be recovered after power failure. > > [1] https://lore.kernel.org/all/CAJpMwyjmHQLvm6zg1cmQErttNNQPDAAXPKM3xgTjMhbfts986Q@xxxxxxxxxxxxxx/ > [2] https://lore.kernel.org/all/ADF7D720-5764-4AF3-B68E-1845988737AA@xxxxxxxxxxxxxxx/ > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> > --- > drivers/md/md.c | 29 +++++++++++++++++++++++++++++ > drivers/md/md.h | 2 ++ > drivers/md/raid1.c | 4 ---- > drivers/md/raid10.c | 3 --- > drivers/md/raid5-cache.c | 2 -- > drivers/md/raid5.c | 24 +----------------------- > 6 files changed, 32 insertions(+), 32 deletions(-) > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index bbe002ebd584..ab37c9939ac6 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -8723,12 +8723,32 @@ void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev, > } > EXPORT_SYMBOL_GPL(md_submit_discard_bio); > > +static void md_bitmap_start(struct mddev *mddev, > + struct md_io_clone *md_io_clone) > +{ > + if (mddev->pers->bitmap_sector) > + mddev->pers->bitmap_sector(mddev, &md_io_clone->offset, > + &md_io_clone->sectors); > + > + mddev->bitmap_ops->startwrite(mddev, md_io_clone->offset, > + md_io_clone->sectors); > +} > + > +static void md_bitmap_end(struct mddev *mddev, struct md_io_clone *md_io_clone) > +{ > + mddev->bitmap_ops->endwrite(mddev, md_io_clone->offset, > + md_io_clone->sectors); > +} > + > static void md_end_clone_io(struct bio *bio) > { > struct md_io_clone *md_io_clone = bio->bi_private; > struct bio *orig_bio = md_io_clone->orig_bio; > struct mddev *mddev = md_io_clone->mddev; > > + if (bio_data_dir(orig_bio) == WRITE && mddev->bitmap) > + md_bitmap_end(mddev, md_io_clone); > + > if (bio->bi_status && !orig_bio->bi_status) > orig_bio->bi_status = bio->bi_status; > > @@ -8753,6 +8773,12 @@ static void md_clone_bio(struct mddev *mddev, struct bio **bio) > if (blk_queue_io_stat(bdev->bd_disk->queue)) > md_io_clone->start_time = bio_start_io_acct(*bio); > > + if (bio_data_dir(*bio) == WRITE && mddev->bitmap) { > + md_io_clone->offset = (*bio)->bi_iter.bi_sector; > + md_io_clone->sectors = bio_sectors(*bio); > + md_bitmap_start(mddev, md_io_clone); > + } > + > clone->bi_end_io = md_end_clone_io; > clone->bi_private = md_io_clone; > *bio = clone; > @@ -8771,6 +8797,9 @@ void md_free_cloned_bio(struct bio *bio) > struct bio *orig_bio = md_io_clone->orig_bio; > struct mddev *mddev = md_io_clone->mddev; > > + if (bio_data_dir(orig_bio) == WRITE && mddev->bitmap) > + md_bitmap_end(mddev, md_io_clone); > + > if (bio->bi_status && !orig_bio->bi_status) > orig_bio->bi_status = bio->bi_status; > > diff --git a/drivers/md/md.h b/drivers/md/md.h > index de6dadb9a40b..def808064ad8 100644 > --- a/drivers/md/md.h > +++ b/drivers/md/md.h > @@ -831,6 +831,8 @@ struct md_io_clone { > struct mddev *mddev; > struct bio *orig_bio; > unsigned long start_time; > + sector_t offset; > + unsigned long sectors; > struct bio bio_clone; > }; > > diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c > index b9819f9c8ed2..e2adfeff5ae6 100644 > --- a/drivers/md/raid1.c > +++ b/drivers/md/raid1.c > @@ -422,8 +422,6 @@ static void close_write(struct r1bio *r1_bio) > > if (test_bit(R1BIO_BehindIO, &r1_bio->state)) > mddev->bitmap_ops->end_behind_write(mddev); > - /* clear the bitmap if all writes complete successfully */ > - mddev->bitmap_ops->endwrite(mddev, r1_bio->sector, r1_bio->sectors); > md_write_end(mddev); > } > > @@ -1616,8 +1614,6 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, > > if (test_bit(R1BIO_BehindIO, &r1_bio->state)) > mddev->bitmap_ops->start_behind_write(mddev); > - mddev->bitmap_ops->startwrite(mddev, r1_bio->sector, > - r1_bio->sectors); > first_clone = 0; > } > > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c > index efbc0bd92479..79a209236c9f 100644 > --- a/drivers/md/raid10.c > +++ b/drivers/md/raid10.c > @@ -428,8 +428,6 @@ static void close_write(struct r10bio *r10_bio) > { > struct mddev *mddev = r10_bio->mddev; > > - /* clear the bitmap if all writes complete successfully */ > - mddev->bitmap_ops->endwrite(mddev, r10_bio->sector, r10_bio->sectors); > md_write_end(mddev); > } > > @@ -1487,7 +1485,6 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio, > md_account_bio(mddev, &bio); > r10_bio->master_bio = bio; > atomic_set(&r10_bio->remaining, 1); > - mddev->bitmap_ops->startwrite(mddev, r10_bio->sector, r10_bio->sectors); > > for (i = 0; i < conf->copies; i++) { > if (r10_bio->devs[i].bio) > diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c > index ba4f9577c737..011246e16a99 100644 > --- a/drivers/md/raid5-cache.c > +++ b/drivers/md/raid5-cache.c > @@ -313,8 +313,6 @@ void r5c_handle_cached_data_endio(struct r5conf *conf, > if (sh->dev[i].written) { > set_bit(R5_UPTODATE, &sh->dev[i].flags); > r5c_return_dev_pending_writes(conf, &sh->dev[i]); > - conf->mddev->bitmap_ops->endwrite(conf->mddev, > - sh->sector, RAID5_STRIPE_SECTORS(conf)); > } > } > } > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index 95caed41654c..976788138a6e 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -3578,12 +3578,6 @@ static void __add_stripe_bio(struct stripe_head *sh, struct bio *bi, > * is added to a batch, STRIPE_BIT_DELAY cannot be changed > * any more. > */ > - set_bit(STRIPE_BITMAP_PENDING, &sh->state); > - spin_unlock_irq(&sh->stripe_lock); > - conf->mddev->bitmap_ops->startwrite(conf->mddev, sh->sector, > - RAID5_STRIPE_SECTORS(conf)); > - spin_lock_irq(&sh->stripe_lock); > - clear_bit(STRIPE_BITMAP_PENDING, &sh->state); > if (!sh->batch_head) { > sh->bm_seq = conf->seq_flush+1; > set_bit(STRIPE_BIT_DELAY, &sh->state); > @@ -3638,7 +3632,6 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, > BUG_ON(sh->batch_head); > for (i = disks; i--; ) { > struct bio *bi; > - int bitmap_end = 0; > > if (test_bit(R5_ReadError, &sh->dev[i].flags)) { > struct md_rdev *rdev = conf->disks[i].rdev; > @@ -3663,8 +3656,6 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, > sh->dev[i].towrite = NULL; > sh->overwrite_disks = 0; > spin_unlock_irq(&sh->stripe_lock); > - if (bi) > - bitmap_end = 1; > > log_stripe_write_finished(sh); > > @@ -3679,10 +3670,6 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, > bio_io_error(bi); > bi = nextbi; > } > - if (bitmap_end) > - conf->mddev->bitmap_ops->endwrite(conf->mddev, > - sh->sector, RAID5_STRIPE_SECTORS(conf)); > - bitmap_end = 0; > /* and fail all 'written' */ > bi = sh->dev[i].written; > sh->dev[i].written = NULL; > @@ -3691,7 +3678,6 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, > sh->dev[i].page = sh->dev[i].orig_page; > } > > - if (bi) bitmap_end = 1; > while (bi && bi->bi_iter.bi_sector < > sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) { > struct bio *bi2 = r5_next_bio(conf, bi, sh->dev[i].sector); > @@ -3725,9 +3711,6 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, > bi = nextbi; > } > } > - if (bitmap_end) > - conf->mddev->bitmap_ops->endwrite(conf->mddev, > - sh->sector, RAID5_STRIPE_SECTORS(conf)); > /* If we were in the middle of a write the parity block might > * still be locked - so just clear all R5_LOCKED flags > */ > @@ -4076,8 +4059,7 @@ static void handle_stripe_clean_event(struct r5conf *conf, > bio_endio(wbi); > wbi = wbi2; > } > - conf->mddev->bitmap_ops->endwrite(conf->mddev, > - sh->sector, RAID5_STRIPE_SECTORS(conf)); > + > if (head_sh->batch_head) { > sh = list_first_entry(&sh->batch_list, > struct stripe_head, > @@ -5797,10 +5779,6 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi) > } > spin_unlock_irq(&sh->stripe_lock); > if (conf->mddev->bitmap) { > - for (d = 0; d < conf->raid_disks - conf->max_degraded; > - d++) > - mddev->bitmap_ops->startwrite(mddev, sh->sector, > - RAID5_STRIPE_SECTORS(conf)); > sh->bm_seq = conf->seq_flush + 1; > set_bit(STRIPE_BIT_DELAY, &sh->state); > } > -- > 2.39.2 > This patch looks good to me. Reviewd-by: Xiao Ni <xni@xxxxxxxxxx>
