md/raid5,6: add percpu scribble region for buffer lists

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>

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