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raid5: add a per-stripe lock
Add a per-stripe lock to protect stripe specific data. The purpose is to reduce lock contention of conf->device_lock. stripe ->toread, ->towrite are protected by per-stripe lock. Accessing bio list of the stripe is always serialized by this lock, so adding bio to the lists (add_stripe_bio()) and removing bio from the lists (like ops_run_biofill()) not race. If bio in ->read, ->written ... list are not shared by multiple stripes, we don't need any lock to protect ->read, ->written, because STRIPE_ACTIVE will protect them. If the bio are shared, there are two protections: 1. bi_phys_segments acts as a reference count 2. traverse the list uses r5_next_bio, which makes traverse never access bio not belonging to the stripe Let's have an example: | stripe1 | stripe2 | stripe3 | ...bio1......|bio2|bio3|....bio4..... stripe2 has 4 bios, when it's finished, it will decrement bi_phys_segments for all bios, but only end_bio for bio2 and bio3. bio1->bi_next still points to bio2, but this doesn't matter. When stripe1 is finished, it will not touch bio2 because of r5_next_bio check. Next time stripe1 will end_bio for bio1 and stripe3 will end_bio bio4. before add_stripe_bio() addes a bio to a stripe, we already increament the bio bi_phys_segments, so don't worry other stripes release the bio. Signed-off-by: Shaohua Li <shli@fusionio.com> Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
parent
7eaf7e8eb3
commit
b17459c050
2 changed files with 20 additions and 16 deletions
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@ -762,14 +762,12 @@ static void ops_complete_biofill(void *stripe_head_ref)
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{
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struct stripe_head *sh = stripe_head_ref;
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struct bio *return_bi = NULL;
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struct r5conf *conf = sh->raid_conf;
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int i;
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pr_debug("%s: stripe %llu\n", __func__,
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(unsigned long long)sh->sector);
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/* clear completed biofills */
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spin_lock_irq(&conf->device_lock);
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for (i = sh->disks; i--; ) {
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struct r5dev *dev = &sh->dev[i];
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@ -795,7 +793,6 @@ static void ops_complete_biofill(void *stripe_head_ref)
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}
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}
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}
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spin_unlock_irq(&conf->device_lock);
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clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
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return_io(return_bi);
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@ -807,7 +804,6 @@ static void ops_complete_biofill(void *stripe_head_ref)
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static void ops_run_biofill(struct stripe_head *sh)
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{
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struct dma_async_tx_descriptor *tx = NULL;
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struct r5conf *conf = sh->raid_conf;
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struct async_submit_ctl submit;
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int i;
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@ -818,10 +814,10 @@ static void ops_run_biofill(struct stripe_head *sh)
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struct r5dev *dev = &sh->dev[i];
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if (test_bit(R5_Wantfill, &dev->flags)) {
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struct bio *rbi;
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spin_lock_irq(&conf->device_lock);
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spin_lock_irq(&sh->stripe_lock);
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dev->read = rbi = dev->toread;
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dev->toread = NULL;
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spin_unlock_irq(&conf->device_lock);
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spin_unlock_irq(&sh->stripe_lock);
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while (rbi && rbi->bi_sector <
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dev->sector + STRIPE_SECTORS) {
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tx = async_copy_data(0, rbi, dev->page,
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@ -1157,12 +1153,12 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
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if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
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struct bio *wbi;
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spin_lock_irq(&sh->raid_conf->device_lock);
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spin_lock_irq(&sh->stripe_lock);
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chosen = dev->towrite;
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dev->towrite = NULL;
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BUG_ON(dev->written);
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wbi = dev->written = chosen;
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spin_unlock_irq(&sh->raid_conf->device_lock);
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spin_unlock_irq(&sh->stripe_lock);
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while (wbi && wbi->bi_sector <
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dev->sector + STRIPE_SECTORS) {
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@ -1467,6 +1463,8 @@ static int grow_one_stripe(struct r5conf *conf)
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init_waitqueue_head(&sh->ops.wait_for_ops);
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#endif
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spin_lock_init(&sh->stripe_lock);
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if (grow_buffers(sh)) {
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shrink_buffers(sh);
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kmem_cache_free(conf->slab_cache, sh);
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@ -2353,8 +2351,15 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
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(unsigned long long)bi->bi_sector,
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(unsigned long long)sh->sector);
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spin_lock_irq(&conf->device_lock);
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/*
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* If several bio share a stripe. The bio bi_phys_segments acts as a
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* reference count to avoid race. The reference count should already be
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* increased before this function is called (for example, in
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* make_request()), so other bio sharing this stripe will not free the
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* stripe. If a stripe is owned by one stripe, the stripe lock will
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* protect it.
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*/
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spin_lock_irq(&sh->stripe_lock);
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if (forwrite) {
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bip = &sh->dev[dd_idx].towrite;
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if (*bip == NULL)
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@ -2388,7 +2393,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
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if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
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set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
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}
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spin_unlock_irq(&conf->device_lock);
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spin_unlock_irq(&sh->stripe_lock);
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pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
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(unsigned long long)(*bip)->bi_sector,
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@ -2404,7 +2409,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
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overlap:
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set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
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spin_unlock_irq(&conf->device_lock);
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spin_unlock_irq(&sh->stripe_lock);
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return 0;
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}
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@ -2454,11 +2459,11 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
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rdev_dec_pending(rdev, conf->mddev);
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}
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}
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spin_lock_irq(&conf->device_lock);
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spin_lock_irq(&sh->stripe_lock);
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/* fail all writes first */
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bi = sh->dev[i].towrite;
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sh->dev[i].towrite = NULL;
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spin_unlock_irq(&conf->device_lock);
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spin_unlock_irq(&sh->stripe_lock);
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if (bi) {
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s->to_write--;
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bitmap_end = 1;
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@ -3192,7 +3197,6 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
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/* Now to look around and see what can be done */
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rcu_read_lock();
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spin_lock_irq(&conf->device_lock);
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for (i=disks; i--; ) {
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struct md_rdev *rdev;
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sector_t first_bad;
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@ -3338,7 +3342,6 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
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do_recovery = 1;
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}
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}
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spin_unlock_irq(&conf->device_lock);
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if (test_bit(STRIPE_SYNCING, &sh->state)) {
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/* If there is a failed device being replaced,
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* we must be recovering.
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@ -210,6 +210,7 @@ struct stripe_head {
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int disks; /* disks in stripe */
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enum check_states check_state;
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enum reconstruct_states reconstruct_state;
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spinlock_t stripe_lock;
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/**
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* struct stripe_operations
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* @target - STRIPE_OP_COMPUTE_BLK target
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