On Mon, 25 Jun 2012 15:24:50 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> Add a per-stripe lock to protect stripe specific data, like dev->read,
> written, ... The purpose is to reduce lock contention of conf->device_lock.
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
I had hoped to avoid having a per-stripe lock again, but it does look like it
is needed.
However I don't like the way you have split up these three patches - it makes
them a little hard to review.
I would like to see one patch which converts the bi_phys_segments access to
be atomic and also removes all the spin_lock calls that were just for
protecting that.
Then another patch which adds the new stripe_lock, clearly documenting
exactly what is protects (not just "like dev->read" but an explicit list)
and also removes any spin_lock of device_lock that is no longer needed.
Then I could see what is being added and what is being removed all in the one
patch and I can be sure that they balance.
Thanks,
NeilBrown
> ---
> drivers/md/raid5.c | 17 +++++++++++++++++
> drivers/md/raid5.h | 1 +
> 2 files changed, 18 insertions(+)
>
> Index: linux/drivers/md/raid5.c
> ===================================================================
> --- linux.orig/drivers/md/raid5.c 2012-06-25 14:36:57.280096788 +0800
> +++ linux/drivers/md/raid5.c 2012-06-25 14:37:13.651888057 +0800
> @@ -751,6 +751,7 @@ static void ops_complete_biofill(void *s
>
> /* clear completed biofills */
> spin_lock_irq(&conf->device_lock);
> + spin_lock(&sh->stripe_lock);
> for (i = sh->disks; i--; ) {
> struct r5dev *dev = &sh->dev[i];
>
> @@ -776,6 +777,7 @@ static void ops_complete_biofill(void *s
> }
> }
> }
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&conf->device_lock);
> clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
>
> @@ -800,8 +802,10 @@ static void ops_run_biofill(struct strip
> if (test_bit(R5_Wantfill, &dev->flags)) {
> struct bio *rbi;
> spin_lock_irq(&conf->device_lock);
> + spin_lock(&sh->stripe_lock);
> dev->read = rbi = dev->toread;
> dev->toread = NULL;
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&conf->device_lock);
> while (rbi && rbi->bi_sector <
> dev->sector + STRIPE_SECTORS) {
> @@ -1139,10 +1143,12 @@ ops_run_biodrain(struct stripe_head *sh,
> struct bio *wbi;
>
> spin_lock_irq(&sh->raid_conf->device_lock);
> + spin_lock(&sh->stripe_lock);
> chosen = dev->towrite;
> dev->towrite = NULL;
> BUG_ON(dev->written);
> wbi = dev->written = chosen;
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&sh->raid_conf->device_lock);
>
> while (wbi && wbi->bi_sector <
> @@ -1448,6 +1454,8 @@ static int grow_one_stripe(struct r5conf
> init_waitqueue_head(&sh->ops.wait_for_ops);
> #endif
>
> + spin_lock_init(&sh->stripe_lock);
> +
> if (grow_buffers(sh)) {
> shrink_buffers(sh);
> kmem_cache_free(conf->slab_cache, sh);
> @@ -2329,6 +2337,7 @@ static int add_stripe_bio(struct stripe_
>
>
> spin_lock_irq(&conf->device_lock);
> + spin_lock(&sh->stripe_lock);
> if (forwrite) {
> bip = &sh->dev[dd_idx].towrite;
> if (*bip == NULL && sh->dev[dd_idx].written == NULL)
> @@ -2362,6 +2371,7 @@ static int add_stripe_bio(struct stripe_
> if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
> set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
> }
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&conf->device_lock);
>
> pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
> @@ -2378,6 +2388,7 @@ static int add_stripe_bio(struct stripe_
>
> overlap:
> set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&conf->device_lock);
> return 0;
> }
> @@ -2429,6 +2440,7 @@ handle_failed_stripe(struct r5conf *conf
> }
> }
> spin_lock_irq(&conf->device_lock);
> + spin_lock(&sh->stripe_lock);
> /* fail all writes first */
> bi = sh->dev[i].towrite;
> sh->dev[i].towrite = NULL;
> @@ -2490,6 +2502,7 @@ handle_failed_stripe(struct r5conf *conf
> bi = nextbi;
> }
> }
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&conf->device_lock);
> if (bitmap_end)
> bitmap_endwrite(conf->mddev->bitmap, sh->sector,
> @@ -2697,6 +2710,7 @@ static void handle_stripe_clean_event(st
> int bitmap_end = 0;
> pr_debug("Return write for disc %d\n", i);
> spin_lock_irq(&conf->device_lock);
> + spin_lock(&sh->stripe_lock);
> wbi = dev->written;
> dev->written = NULL;
> while (wbi && wbi->bi_sector <
> @@ -2711,6 +2725,7 @@ static void handle_stripe_clean_event(st
> }
> if (dev->towrite == NULL)
> bitmap_end = 1;
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&conf->device_lock);
> if (bitmap_end)
> bitmap_endwrite(conf->mddev->bitmap,
> @@ -3170,6 +3185,7 @@ static void analyse_stripe(struct stripe
> /* Now to look around and see what can be done */
> rcu_read_lock();
> spin_lock_irq(&conf->device_lock);
> + spin_lock(&sh->stripe_lock);
> for (i=disks; i--; ) {
> struct md_rdev *rdev;
> sector_t first_bad;
> @@ -3315,6 +3331,7 @@ static void analyse_stripe(struct stripe
> do_recovery = 1;
> }
> }
> + spin_unlock(&sh->stripe_lock);
> spin_unlock_irq(&conf->device_lock);
> if (test_bit(STRIPE_SYNCING, &sh->state)) {
> /* If there is a failed device being replaced,
> Index: linux/drivers/md/raid5.h
> ===================================================================
> --- linux.orig/drivers/md/raid5.h 2012-06-25 14:36:13.940638627 +0800
> +++ linux/drivers/md/raid5.h 2012-06-25 14:37:13.651888057 +0800
> @@ -210,6 +210,7 @@ struct stripe_head {
> int disks; /* disks in stripe */
> enum check_states check_state;
> enum reconstruct_states reconstruct_state;
> + spinlock_t stripe_lock;
> /**
> * struct stripe_operations
> * @target - STRIPE_OP_COMPUTE_BLK target
Attachment:
signature.asc
Description: PGP signature
