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Subject[PATCH v3 07/14] md/raid5, 6: add percpu scribble region for buffer lists
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Date
Use percpu memory rather than stack for storing the buffer lists used in
parity calculations. Include space for dma address conversions and pass
that to async_tx via the async_submit_ctl.scribble pointer.

[ Impact: move memory pressure from stack to heap ]

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/md/raid5.c | 132 ++++++++++++++++++++++++++++++++++++++++------------
drivers/md/raid5.h | 8 +++
2 files changed, 110 insertions(+), 30 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5359236..7727954 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -642,11 +642,18 @@ static void ops_complete_compute5(void *stripe_head_ref)
release_stripe(sh);
}

-static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
+/* return a pointer to the address conversion region of the scribble buffer */
+static addr_conv_t *to_addr_conv(struct stripe_head *sh,
+ struct raid5_percpu *percpu)
+{
+ return percpu->scribble + sizeof(struct page *) * (sh->disks + 2);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute5(struct stripe_head *sh, struct raid5_percpu *percpu)
{
- /* kernel stack size limits the total number of disks */
int disks = sh->disks;
- struct page *xor_srcs[disks];
+ struct page **xor_srcs = percpu->scribble;
int target = sh->ops.target;
struct r5dev *tgt = &sh->dev[target];
struct page *xor_dest = tgt->page;
@@ -666,7 +673,7 @@ static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
atomic_inc(&sh->count);

init_async_submit(&submit, ASYNC_TX_XOR_ZERO_DST, NULL,
- ops_complete_compute5, sh, NULL);
+ ops_complete_compute5, sh, to_addr_conv(sh, percpu));
if (unlikely(count == 1))
tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE, &submit);
else
@@ -684,11 +691,11 @@ static void ops_complete_prexor(void *stripe_head_ref)
}

static struct dma_async_tx_descriptor *
-ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+ops_run_prexor(struct stripe_head *sh, struct raid5_percpu *percpu,
+ struct dma_async_tx_descriptor *tx)
{
- /* kernel stack size limits the total number of disks */
int disks = sh->disks;
- struct page *xor_srcs[disks];
+ struct page **xor_srcs = percpu->scribble;
int count = 0, pd_idx = sh->pd_idx, i;
struct async_submit_ctl submit;

@@ -706,7 +713,7 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
}

init_async_submit(&submit, ASYNC_TX_XOR_DROP_DST, tx,
- ops_complete_prexor, sh, NULL);
+ ops_complete_prexor, sh, to_addr_conv(sh, percpu));
tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE, &submit);

return tx;
@@ -775,11 +782,11 @@ static void ops_complete_postxor(void *stripe_head_ref)
}

static void
-ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+ops_run_postxor(struct stripe_head *sh, struct raid5_percpu *percpu,
+ struct dma_async_tx_descriptor *tx)
{
- /* kernel stack size limits the total number of disks */
int disks = sh->disks;
- struct page *xor_srcs[disks];
+ struct page **xor_srcs = percpu->scribble;
struct async_submit_ctl submit;
int count = 0, pd_idx = sh->pd_idx, i;
struct page *xor_dest;
@@ -819,7 +826,8 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)

atomic_inc(&sh->count);

- init_async_submit(&submit, flags, tx, ops_complete_postxor, sh, NULL);
+ init_async_submit(&submit, flags, tx, ops_complete_postxor, sh,
+ to_addr_conv(sh, percpu));
if (unlikely(count == 1))
tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE, &submit);
else
@@ -838,11 +846,10 @@ static void ops_complete_check(void *stripe_head_ref)
release_stripe(sh);
}

-static void ops_run_check(struct stripe_head *sh)
+static void ops_run_check(struct stripe_head *sh, struct raid5_percpu *percpu)
{
- /* kernel stack size limits the total number of disks */
int disks = sh->disks;
- struct page *xor_srcs[disks];
+ struct page **xor_srcs = percpu->scribble;
struct dma_async_tx_descriptor *tx;
struct async_submit_ctl submit;

@@ -858,7 +865,8 @@ static void ops_run_check(struct stripe_head *sh)
xor_srcs[count++] = dev->page;
}

- init_async_submit(&submit, 0, NULL, NULL, NULL, NULL);
+ init_async_submit(&submit, 0, NULL, NULL, NULL,
+ to_addr_conv(sh, percpu));
tx = async_xor_val(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
&sh->ops.zero_sum_result, &submit);

@@ -871,21 +879,26 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
{
int overlap_clear = 0, i, disks = sh->disks;
struct dma_async_tx_descriptor *tx = NULL;
+ raid5_conf_t *conf = sh->raid_conf;
+ struct raid5_percpu *percpu;
+ unsigned long cpu;

+ cpu = get_cpu();
+ percpu = per_cpu_ptr(conf->percpu, cpu);
if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
ops_run_biofill(sh);
overlap_clear++;
}

if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request)) {
- tx = ops_run_compute5(sh);
+ tx = ops_run_compute5(sh, percpu);
/* terminate the chain if postxor is not set to be run */
if (tx && !test_bit(STRIPE_OP_POSTXOR, &ops_request))
async_tx_ack(tx);
}

if (test_bit(STRIPE_OP_PREXOR, &ops_request))
- tx = ops_run_prexor(sh, tx);
+ tx = ops_run_prexor(sh, percpu, tx);

if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
tx = ops_run_biodrain(sh, tx);
@@ -893,10 +906,10 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
}

if (test_bit(STRIPE_OP_POSTXOR, &ops_request))
- ops_run_postxor(sh, tx);
+ ops_run_postxor(sh, percpu, tx);

if (test_bit(STRIPE_OP_CHECK, &ops_request))
- ops_run_check(sh);
+ ops_run_check(sh, percpu);

if (overlap_clear)
for (i = disks; i--; ) {
@@ -904,6 +917,7 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
if (test_and_clear_bit(R5_Overlap, &dev->flags))
wake_up(&sh->raid_conf->wait_for_overlap);
}
+ put_cpu();
}

static int grow_one_stripe(raid5_conf_t *conf)
@@ -953,6 +967,28 @@ static int grow_stripes(raid5_conf_t *conf, int num)
return 0;
}

+/**
+ * scribble_len - return the required size of the scribble region
+ * @num - total number of disks in the array
+ *
+ * The size must be enough to contain:
+ * 1/ a struct page pointer for each device in the array +2
+ * 2/ room to convert each entry in (1) to its corresponding dma
+ * (dma_map_page()) or page (page_address()) address.
+ *
+ * Note: the +2 is for the destination buffers of the ddf/raid6 case where we
+ * calculate over all devices (not just the data blocks), using zeros in place
+ * of the P and Q blocks.
+ */
+static size_t scribble_len(int num)
+{
+ size_t len;
+
+ len = sizeof(struct page *) * (num+2) + sizeof(addr_conv_t) * (num+2);
+
+ return len;
+}
+
static int resize_stripes(raid5_conf_t *conf, int newsize)
{
/* Make all the stripes able to hold 'newsize' devices.
@@ -981,6 +1017,7 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
struct stripe_head *osh, *nsh;
LIST_HEAD(newstripes);
struct disk_info *ndisks;
+ unsigned long cpu;
int err;
struct kmem_cache *sc;
int i;
@@ -1046,7 +1083,7 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
/* Step 3.
* At this point, we are holding all the stripes so the array
* is completely stalled, so now is a good time to resize
- * conf->disks.
+ * conf->disks and the scribble region
*/
ndisks = kzalloc(newsize * sizeof(struct disk_info), GFP_NOIO);
if (ndisks) {
@@ -1057,10 +1094,30 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
} else
err = -ENOMEM;

+ get_online_cpus();
+ conf->scribble_len = scribble_len(newsize);
+ for_each_present_cpu(cpu) {
+ struct raid5_percpu *percpu;
+ void *scribble;
+
+ percpu = per_cpu_ptr(conf->percpu, cpu);
+ scribble = kmalloc(conf->scribble_len, GFP_NOIO);
+
+ if (scribble) {
+ kfree(percpu->scribble);
+ percpu->scribble = scribble;
+ } else {
+ err = -ENOMEM;
+ break;
+ }
+ }
+ put_online_cpus();
+
/* Step 4, return new stripes to service */
while(!list_empty(&newstripes)) {
nsh = list_entry(newstripes.next, struct stripe_head, lru);
list_del_init(&nsh->lru);
+
for (i=conf->raid_disks; i < newsize; i++)
if (nsh->dev[i].page == NULL) {
struct page *p = alloc_page(GFP_NOIO);
@@ -4318,6 +4375,7 @@ static void raid5_free_percpu(raid5_conf_t *conf)
for_each_possible_cpu(cpu) {
percpu = per_cpu_ptr(conf->percpu, cpu);
safe_put_page(percpu->spare_page);
+ kfree(percpu->scribble);
}
#ifdef CONFIG_HOTPLUG_CPU
unregister_cpu_notifier(&conf->cpu_notify);
@@ -4347,9 +4405,15 @@ static int raid456_cpu_notify(struct notifier_block *nfb, unsigned long action,
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- if (!percpu->spare_page)
+ if (conf->level == 6 && !percpu->spare_page)
percpu->spare_page = alloc_page(GFP_KERNEL);
- if (!percpu->spare_page) {
+ if (!percpu->scribble)
+ percpu->scribble = kmalloc(conf->scribble_len, GFP_KERNEL);
+
+ if (!percpu->scribble ||
+ (conf->level == 6 && !percpu->spare_page)) {
+ safe_put_page(percpu->spare_page);
+ kfree(percpu->scribble);
pr_err("%s: failed memory allocation for cpu%ld\n",
__func__, cpu);
return NOTIFY_BAD;
@@ -4358,7 +4422,9 @@ static int raid456_cpu_notify(struct notifier_block *nfb, unsigned long action,
case CPU_DEAD:
case CPU_DEAD_FROZEN:
safe_put_page(percpu->spare_page);
+ kfree(percpu->scribble);
percpu->spare_page = NULL;
+ percpu->scribble = NULL;
break;
default:
break;
@@ -4372,12 +4438,9 @@ static int raid5_alloc_percpu(raid5_conf_t *conf)
unsigned long cpu;
struct page *spare_page;
struct raid5_percpu *allcpus;
+ void *scribble;
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;
@@ -4386,12 +4449,20 @@ static int raid5_alloc_percpu(raid5_conf_t *conf)
get_online_cpus();
err = 0;
for_each_present_cpu(cpu) {
- spare_page = alloc_page(GFP_KERNEL);
- if (!spare_page) {
+ if (conf->level == 6) {
+ spare_page = alloc_page(GFP_KERNEL);
+ if (!spare_page) {
+ err = -ENOMEM;
+ break;
+ }
+ per_cpu_ptr(conf->percpu, cpu)->spare_page = spare_page;
+ }
+ scribble = kmalloc(scribble_len(conf->raid_disks), GFP_KERNEL);
+ if (!scribble) {
err = -ENOMEM;
break;
}
- per_cpu_ptr(conf->percpu, cpu)->spare_page = spare_page;
+ per_cpu_ptr(conf->percpu, cpu)->scribble = scribble;
}
#ifdef CONFIG_HOTPLUG_CPU
conf->cpu_notify.notifier_call = raid456_cpu_notify;
@@ -4443,6 +4514,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
goto abort;

conf->raid_disks = mddev->raid_disks;
+ conf->scribble_len = scribble_len(conf->raid_disks);
if (mddev->reshape_position == MaxSector)
conf->previous_raid_disks = mddev->raid_disks;
else
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 07a7a41..e7baabf 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -386,7 +386,15 @@ struct raid5_private_data {
/* per cpu variables */
struct raid5_percpu {
struct page *spare_page; /* Used when checking P/Q in raid6 */
+ void *scribble; /* space for constructing buffer
+ * lists and performing address
+ * conversions
+ */
} *percpu;
+ size_t scribble_len; /* size of scribble region must be
+ * associated with conf to handle
+ * cpu hotplug while reshaping
+ */
#ifdef CONFIG_HOTPLUG_CPU
struct notifier_block cpu_notify;
#endif


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