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SubjectRe: [PATCH 1/2] md/raid5: avoid duplicate code
On Wed,  6 May 2015 17:45:49 +0800 Yuanhan Liu <yuanhan.liu@linux.intel.com>
wrote:

> Move the code that put one idle sh(hot in cache, but happens to be
> zero referenced) back to active stage to __find_stripe(). Because
> that's what need to do every time you invoke __find_stripe().
>
> Moving it there avoids duplicate code, as well as makes a bit more
> sense, IMO, as it tells a whole story now.

Thanks for this. It is a good cleanup.

However I don't want to make any new changes to the RAID5 code until I find a
couple of bugs that I'm hunting. So I won't apply it just yet.
Remind me in a couple of weeks if I seem to have forgotten.

Thanks,
NeilBrown


>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
> drivers/md/raid5.c | 50 ++++++++++++++++++--------------------------------
> 1 file changed, 18 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 77dfd72..e7fa818 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -567,8 +567,25 @@ static struct stripe_head *__find_stripe(struct r5conf *conf, sector_t sector,
>
> pr_debug("__find_stripe, sector %llu\n", (unsigned long long)sector);
> hlist_for_each_entry(sh, stripe_hash(conf, sector), hash)
> - if (sh->sector == sector && sh->generation == generation)
> + if (sh->sector == sector && sh->generation == generation) {
> + if (!atomic_inc_not_zero(&sh->count)) {
> + spin_lock(&conf->device_lock);
> + if (!atomic_read(&sh->count)) {
> + if (!test_bit(STRIPE_HANDLE, &sh->state))
> + atomic_inc(&conf->active_stripes);
> + BUG_ON(list_empty(&sh->lru) &&
> + !test_bit(STRIPE_EXPANDING, &sh->state));
> + list_del_init(&sh->lru);
> + if (sh->group) {
> + sh->group->stripes_cnt--;
> + sh->group = NULL;
> + }
> + }
> + atomic_inc(&sh->count);
> + spin_unlock(&conf->device_lock);
> + }
> return sh;
> + }
> pr_debug("__stripe %llu not in cache\n", (unsigned long long)sector);
> return NULL;
> }
> @@ -698,21 +715,6 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
> init_stripe(sh, sector, previous);
> atomic_inc(&sh->count);
> }
> - } else if (!atomic_inc_not_zero(&sh->count)) {
> - spin_lock(&conf->device_lock);
> - if (!atomic_read(&sh->count)) {
> - if (!test_bit(STRIPE_HANDLE, &sh->state))
> - atomic_inc(&conf->active_stripes);
> - BUG_ON(list_empty(&sh->lru) &&
> - !test_bit(STRIPE_EXPANDING, &sh->state));
> - list_del_init(&sh->lru);
> - if (sh->group) {
> - sh->group->stripes_cnt--;
> - sh->group = NULL;
> - }
> - }
> - atomic_inc(&sh->count);
> - spin_unlock(&conf->device_lock);
> }
> } while (sh == NULL);
>
> @@ -771,22 +773,6 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh
> hash = stripe_hash_locks_hash(head_sector);
> spin_lock_irq(conf->hash_locks + hash);
> head = __find_stripe(conf, head_sector, conf->generation);
> - if (head && !atomic_inc_not_zero(&head->count)) {
> - spin_lock(&conf->device_lock);
> - if (!atomic_read(&head->count)) {
> - if (!test_bit(STRIPE_HANDLE, &head->state))
> - atomic_inc(&conf->active_stripes);
> - BUG_ON(list_empty(&head->lru) &&
> - !test_bit(STRIPE_EXPANDING, &head->state));
> - list_del_init(&head->lru);
> - if (head->group) {
> - head->group->stripes_cnt--;
> - head->group = NULL;
> - }
> - }
> - atomic_inc(&head->count);
> - spin_unlock(&conf->device_lock);
> - }
> spin_unlock_irq(conf->hash_locks + hash);
>
> if (!head)

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