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Subject[PATCH v3 06/14] md/raid6: move the spare page to a percpu allocation
From
Date
In preparation for asynchronous handling of raid6 operations move the
spare page to a percpu allocation to allow multiple simultaneous
synchronous raid6 recovery operations.

Make this allocation cpu hotplug aware to maximize allocation
efficiency.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/md/raid5.c | 252 +++++++++++++++++++++++++++++++++++-----------------
drivers/md/raid5.h | 9 +-
2 files changed, 175 insertions(+), 86 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9411466..5359236 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -48,6 +48,7 @@
#include <linux/raid/pq.h>
#include <linux/async_tx.h>
#include <linux/seq_file.h>
+#include <linux/cpu.h>
#include "md.h"
#include "raid5.h"
#include "bitmap.h"
@@ -2565,14 +2566,15 @@ static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,


static void handle_parity_checks6(raid5_conf_t *conf, struct stripe_head *sh,
- struct stripe_head_state *s,
- struct r6_state *r6s, struct page *tmp_page,
- int disks)
+ struct stripe_head_state *s,
+ struct r6_state *r6s, int disks)
{
int update_p = 0, update_q = 0;
struct r5dev *dev;
int pd_idx = sh->pd_idx;
int qd_idx = sh->qd_idx;
+ unsigned long cpu;
+ struct page *tmp_page;

set_bit(STRIPE_HANDLE, &sh->state);

@@ -2583,78 +2585,75 @@ static void handle_parity_checks6(raid5_conf_t *conf, struct stripe_head *sh,
* case we can only check one of them, possibly using the
* other to generate missing data
*/
-
- /* If !tmp_page, we cannot do the calculations,
- * but as we have set STRIPE_HANDLE, we will soon be called
- * by stripe_handle with a tmp_page - just wait until then.
- */
- if (tmp_page) {
- if (s->failed == r6s->q_failed) {
- /* The only possible failed device holds 'Q', so it
- * makes sense to check P (If anything else were failed,
- * we would have used P to recreate it).
- */
- compute_block_1(sh, pd_idx, 1);
- if (!page_is_zero(sh->dev[pd_idx].page)) {
- compute_block_1(sh, pd_idx, 0);
- update_p = 1;
- }
- }
- if (!r6s->q_failed && s->failed < 2) {
- /* q is not failed, and we didn't use it to generate
- * anything, so it makes sense to check it
- */
- memcpy(page_address(tmp_page),
- page_address(sh->dev[qd_idx].page),
- STRIPE_SIZE);
- compute_parity6(sh, UPDATE_PARITY);
- if (memcmp(page_address(tmp_page),
- page_address(sh->dev[qd_idx].page),
- STRIPE_SIZE) != 0) {
- clear_bit(STRIPE_INSYNC, &sh->state);
- update_q = 1;
- }
+ cpu = get_cpu();
+ tmp_page = per_cpu_ptr(conf->percpu, cpu)->spare_page;
+ if (s->failed == r6s->q_failed) {
+ /* The only possible failed device holds 'Q', so it
+ * makes sense to check P (If anything else were failed,
+ * we would have used P to recreate it).
+ */
+ compute_block_1(sh, pd_idx, 1);
+ if (!page_is_zero(sh->dev[pd_idx].page)) {
+ compute_block_1(sh, pd_idx, 0);
+ update_p = 1;
}
- if (update_p || update_q) {
- conf->mddev->resync_mismatches += STRIPE_SECTORS;
- if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
- /* don't try to repair!! */
- update_p = update_q = 0;
+ }
+ if (!r6s->q_failed && s->failed < 2) {
+ /* q is not failed, and we didn't use it to generate
+ * anything, so it makes sense to check it
+ */
+ memcpy(page_address(tmp_page),
+ page_address(sh->dev[qd_idx].page),
+ STRIPE_SIZE);
+ compute_parity6(sh, UPDATE_PARITY);
+ if (memcmp(page_address(tmp_page),
+ page_address(sh->dev[qd_idx].page),
+ STRIPE_SIZE) != 0) {
+ clear_bit(STRIPE_INSYNC, &sh->state);
+ update_q = 1;
}
+ }
+ put_cpu();

- /* now write out any block on a failed drive,
- * or P or Q if they need it
- */
+ if (update_p || update_q) {
+ conf->mddev->resync_mismatches += STRIPE_SECTORS;
+ if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
+ /* don't try to repair!! */
+ update_p = update_q = 0;
+ }

- if (s->failed == 2) {
- dev = &sh->dev[r6s->failed_num[1]];
- s->locked++;
- set_bit(R5_LOCKED, &dev->flags);
- set_bit(R5_Wantwrite, &dev->flags);
- }
- if (s->failed >= 1) {
- dev = &sh->dev[r6s->failed_num[0]];
- s->locked++;
- set_bit(R5_LOCKED, &dev->flags);
- set_bit(R5_Wantwrite, &dev->flags);
- }
+ /* now write out any block on a failed drive,
+ * or P or Q if they need it
+ */

- if (update_p) {
- dev = &sh->dev[pd_idx];
- s->locked++;
- set_bit(R5_LOCKED, &dev->flags);
- set_bit(R5_Wantwrite, &dev->flags);
- }
- if (update_q) {
- dev = &sh->dev[qd_idx];
- s->locked++;
- set_bit(R5_LOCKED, &dev->flags);
- set_bit(R5_Wantwrite, &dev->flags);
- }
- clear_bit(STRIPE_DEGRADED, &sh->state);
+ if (s->failed == 2) {
+ dev = &sh->dev[r6s->failed_num[1]];
+ s->locked++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
+ }
+ if (s->failed >= 1) {
+ dev = &sh->dev[r6s->failed_num[0]];
+ s->locked++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
+ }

- set_bit(STRIPE_INSYNC, &sh->state);
+ if (update_p) {
+ dev = &sh->dev[pd_idx];
+ s->locked++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
+ }
+ if (update_q) {
+ dev = &sh->dev[qd_idx];
+ s->locked++;
+ set_bit(R5_LOCKED, &dev->flags);
+ set_bit(R5_Wantwrite, &dev->flags);
}
+ clear_bit(STRIPE_DEGRADED, &sh->state);
+
+ set_bit(STRIPE_INSYNC, &sh->state);
}

static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
@@ -3009,7 +3008,7 @@ static bool handle_stripe5(struct stripe_head *sh)
return blocked_rdev == NULL;
}

-static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
+static bool handle_stripe6(struct stripe_head *sh)
{
raid5_conf_t *conf = sh->raid_conf;
int disks = sh->disks;
@@ -3164,7 +3163,7 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
* data is available
*/
if (s.syncing && s.locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state))
- handle_parity_checks6(conf, sh, &s, &r6s, tmp_page, disks);
+ handle_parity_checks6(conf, sh, &s, &r6s, disks);

if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
md_done_sync(conf->mddev, STRIPE_SECTORS,1);
@@ -3247,16 +3246,14 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
}

/* returns true if the stripe was handled */
-static bool handle_stripe(struct stripe_head *sh, struct page *tmp_page)
+static bool handle_stripe(struct stripe_head *sh)
{
if (sh->raid_conf->level == 6)
- return handle_stripe6(sh, tmp_page);
+ return handle_stripe6(sh);
else
return handle_stripe5(sh);
}

-
-
static void raid5_activate_delayed(raid5_conf_t *conf)
{
if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
@@ -4047,7 +4044,7 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski
spin_unlock(&sh->lock);

/* wait for any blocked device to be handled */
- while(unlikely(!handle_stripe(sh, NULL)))
+ while (unlikely(!handle_stripe(sh)))
;
release_stripe(sh);

@@ -4104,7 +4101,7 @@ static int retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
return handled;
}

- handle_stripe(sh, NULL);
+ handle_stripe(sh);
release_stripe(sh);
handled++;
}
@@ -4168,7 +4165,7 @@ static void raid5d(mddev_t *mddev)
spin_unlock_irq(&conf->device_lock);

handled++;
- handle_stripe(sh, conf->spare_page);
+ handle_stripe(sh);
release_stripe(sh);

spin_lock_irq(&conf->device_lock);
@@ -4309,15 +4306,104 @@ raid5_size(mddev_t *mddev, sector_t sectors, int raid_disks)
return sectors * (raid_disks - conf->max_degraded);
}

+static void raid5_free_percpu(raid5_conf_t *conf)
+{
+ struct raid5_percpu *percpu;
+ unsigned long cpu;
+
+ if (!conf->percpu)
+ return;
+
+ get_online_cpus();
+ for_each_possible_cpu(cpu) {
+ percpu = per_cpu_ptr(conf->percpu, cpu);
+ safe_put_page(percpu->spare_page);
+ }
+#ifdef CONFIG_HOTPLUG_CPU
+ unregister_cpu_notifier(&conf->cpu_notify);
+#endif
+ put_online_cpus();
+
+ free_percpu(conf->percpu);
+}
+
static void free_conf(raid5_conf_t *conf)
{
shrink_stripes(conf);
- safe_put_page(conf->spare_page);
+ raid5_free_percpu(conf);
kfree(conf->disks);
kfree(conf->stripe_hashtbl);
kfree(conf);
}

+#ifdef CONFIG_HOTPLUG_CPU
+static int raid456_cpu_notify(struct notifier_block *nfb, unsigned long action,
+ void *hcpu)
+{
+ raid5_conf_t *conf = container_of(nfb, raid5_conf_t, cpu_notify);
+ long cpu = (long)hcpu;
+ struct raid5_percpu *percpu = per_cpu_ptr(conf->percpu, cpu);
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ case CPU_UP_PREPARE_FROZEN:
+ if (!percpu->spare_page)
+ percpu->spare_page = alloc_page(GFP_KERNEL);
+ if (!percpu->spare_page) {
+ pr_err("%s: failed memory allocation for cpu%ld\n",
+ __func__, cpu);
+ return NOTIFY_BAD;
+ }
+ break;
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ safe_put_page(percpu->spare_page);
+ percpu->spare_page = NULL;
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+#endif
+
+static int raid5_alloc_percpu(raid5_conf_t *conf)
+{
+ unsigned long cpu;
+ struct page *spare_page;
+ struct raid5_percpu *allcpus;
+ int err;
+
+ /* the only percpu data is the raid6 spare page */
+ if (conf->level != 6)
+ return 0;
+
+ allcpus = alloc_percpu(struct raid5_percpu);
+ if (!allcpus)
+ return -ENOMEM;
+ conf->percpu = allcpus;
+
+ get_online_cpus();
+ err = 0;
+ for_each_present_cpu(cpu) {
+ spare_page = alloc_page(GFP_KERNEL);
+ if (!spare_page) {
+ err = -ENOMEM;
+ break;
+ }
+ per_cpu_ptr(conf->percpu, cpu)->spare_page = spare_page;
+ }
+#ifdef CONFIG_HOTPLUG_CPU
+ conf->cpu_notify.notifier_call = raid456_cpu_notify;
+ conf->cpu_notify.priority = 0;
+ if (err == 0)
+ err = register_cpu_notifier(&conf->cpu_notify);
+#endif
+ put_online_cpus();
+
+ return err;
+}
+
static raid5_conf_t *setup_conf(mddev_t *mddev)
{
raid5_conf_t *conf;
@@ -4372,11 +4458,10 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
goto abort;

- if (mddev->new_level == 6) {
- conf->spare_page = alloc_page(GFP_KERNEL);
- if (!conf->spare_page)
- goto abort;
- }
+ conf->level = mddev->new_level;
+ if (raid5_alloc_percpu(conf) != 0)
+ goto abort;
+
spin_lock_init(&conf->device_lock);
init_waitqueue_head(&conf->wait_for_stripe);
init_waitqueue_head(&conf->wait_for_overlap);
@@ -4412,7 +4497,6 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
}

conf->chunk_size = mddev->new_chunk;
- conf->level = mddev->new_level;
if (conf->level == 6)
conf->max_degraded = 2;
else
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 52ba999..07a7a41 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -383,8 +383,13 @@ struct raid5_private_data {
* (fresh device added).
* Cleared when a sync completes.
*/
-
- struct page *spare_page; /* Used when checking P/Q in raid6 */
+ /* per cpu variables */
+ struct raid5_percpu {
+ struct page *spare_page; /* Used when checking P/Q in raid6 */
+ } *percpu;
+#ifdef CONFIG_HOTPLUG_CPU
+ struct notifier_block cpu_notify;
+#endif

/*
* Free stripes pool


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