diff options
author | NeilBrown <neilb@suse.de> | 2015-05-27 08:43:45 +1000 |
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committer | NeilBrown <neilb@suse.de> | 2015-05-28 11:34:40 +1000 |
commit | d0852df543e5aa7db34c1ad26d053782bcbf48f1 (patch) | |
tree | 0276829b09beb6d16a4349afe2c75b3eaed80d47 /drivers/md/raid5.c | |
parent | 2b6b24574256c05be145936f1493aec74c6904e5 (diff) | |
download | op-kernel-dev-d0852df543e5aa7db34c1ad26d053782bcbf48f1.zip op-kernel-dev-d0852df543e5aa7db34c1ad26d053782bcbf48f1.tar.gz |
md/raid5: close race between STRIPE_BIT_DELAY and batching.
When we add a write to a stripe we need to make sure the bitmap
bit is set. While doing that the stripe is not locked so it could
be added to a batch after which further changes to STRIPE_BIT_DELAY
and ->bm_seq are ineffective.
So we need to hold off adding to a stripe until bitmap_startwrite has
completed at least once, and we need to avoid further changes to
STRIPE_BIT_DELAY once the stripe has been added to a batch.
If a bitmap_startwrite() completes after the stripe was added to a
batch, it will not have set the bit, only incremented a counter, so no
extra delay of the stripe is needed.
Reported-by: Shaohua Li <shli@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'drivers/md/raid5.c')
-rw-r--r-- | drivers/md/raid5.c | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index c55a68f..42d0ea6 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -749,6 +749,7 @@ static void unlock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2) static bool stripe_can_batch(struct stripe_head *sh) { return test_bit(STRIPE_BATCH_READY, &sh->state) && + !test_bit(STRIPE_BITMAP_PENDING, &sh->state) && is_full_stripe_write(sh); } @@ -2996,14 +2997,32 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n", (unsigned long long)(*bip)->bi_iter.bi_sector, (unsigned long long)sh->sector, dd_idx); - spin_unlock_irq(&sh->stripe_lock); if (conf->mddev->bitmap && firstwrite) { + /* Cannot hold spinlock over bitmap_startwrite, + * but must ensure this isn't added to a batch until + * we have added to the bitmap and set bm_seq. + * So set STRIPE_BITMAP_PENDING to prevent + * batching. + * If multiple add_stripe_bio() calls race here they + * much all set STRIPE_BITMAP_PENDING. So only the first one + * to complete "bitmap_startwrite" gets to set + * STRIPE_BIT_DELAY. This is important as once a stripe + * 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); bitmap_startwrite(conf->mddev->bitmap, sh->sector, STRIPE_SECTORS, 0); - sh->bm_seq = conf->seq_flush+1; - set_bit(STRIPE_BIT_DELAY, &sh->state); + 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); + } } + spin_unlock_irq(&sh->stripe_lock); if (stripe_can_batch(sh)) stripe_add_to_batch_list(conf, sh); |