s390/scm_block: force cluster writes

Force writes to Storage Class Memory (SCM) to be in done in clusters.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

5 files changed, 310 insertions, 3 deletions

diff --git a/drivers/s390/block/Kconfig b/drivers/s390/block/Kconfig
index 18178b64e89a..4a3b62326183 100644
--- a/drivers/s390/block/Kconfig
+++ b/drivers/s390/block/Kconfig
@@ -81,3 +81,10 @@ config SCM_BLOCK
 
           To compile this driver as a module, choose M here: the
           module will be called scm_block.
+
+config SCM_BLOCK_CLUSTER_WRITE
+        def_bool y
+        prompt "SCM force cluster writes"
+        depends on SCM_BLOCK
+        help
+          Force writes to Storage Class Memory (SCM) to be in done in clusters.
diff --git a/drivers/s390/block/Makefile b/drivers/s390/block/Makefile
index b64e2b32c753..c2f4e673e031 100644
--- a/drivers/s390/block/Makefile
+++ b/drivers/s390/block/Makefile
@@ -19,4 +19,7 @@ obj-$(CONFIG_BLK_DEV_XPRAM) += xpram.o
 obj-$(CONFIG_DCSSBLK) += dcssblk.o
 
 scm_block-objs := scm_drv.o scm_blk.o
+ifdef CONFIG_SCM_BLOCK_CLUSTER_WRITE
+scm_block-objs += scm_blk_cluster.o
+endif
 obj-$(CONFIG_SCM_BLOCK) += scm_block.o
diff --git a/drivers/s390/block/scm_blk.c b/drivers/s390/block/scm_blk.c
index 634ad58cbef6..9978ad4433cb 100644
--- a/drivers/s390/block/scm_blk.c
+++ b/drivers/s390/block/scm_blk.c
@@ -37,6 +37,7 @@ static void __scm_free_rq(struct scm_request *scmrq)
 
         free_page((unsigned long) scmrq->aob);
         free_page((unsigned long) scmrq->aidaw);
+        __scm_free_rq_cluster(scmrq);
         kfree(aobrq);
 }
 
@@ -70,6 +71,12 @@ static int __scm_alloc_rq(void)
                 __scm_free_rq(scmrq);
                 return -ENOMEM;
         }
+
+        if (__scm_alloc_rq_cluster(scmrq)) {
+                __scm_free_rq(scmrq);
+                return -ENOMEM;
+        }
+
         INIT_LIST_HEAD(&scmrq->list);
         spin_lock_irq(&list_lock);
         list_add(&scmrq->list, &inactive_requests);
@@ -170,6 +177,7 @@ static inline void scm_request_init(struct scm_blk_dev *bdev,
         scmrq->bdev = bdev;
         scmrq->retries = 4;
         scmrq->error = 0;
+        scm_request_cluster_init(scmrq);
 }
 
 static void scm_ensure_queue_restart(struct scm_blk_dev *bdev)
@@ -181,17 +189,19 @@ static void scm_ensure_queue_restart(struct scm_blk_dev *bdev)
         blk_delay_queue(bdev->rq, SCM_QUEUE_DELAY);
 }
 
-static void scm_request_requeue(struct scm_request *scmrq)
+void scm_request_requeue(struct scm_request *scmrq)
 {
         struct scm_blk_dev *bdev = scmrq->bdev;
 
+        scm_release_cluster(scmrq);
         blk_requeue_request(bdev->rq, scmrq->request);
         scm_request_done(scmrq);
         scm_ensure_queue_restart(bdev);
 }
 
-static void scm_request_finish(struct scm_request *scmrq)
+void scm_request_finish(struct scm_request *scmrq)
 {
+        scm_release_cluster(scmrq);
         blk_end_request_all(scmrq->request, scmrq->error);
         scm_request_done(scmrq);
 }
@@ -215,6 +225,16 @@ static void scm_blk_request(struct request_queue *rq)
                         return;
                 }
                 scm_request_init(bdev, scmrq, req);
+                if (!scm_reserve_cluster(scmrq)) {
+                        SCM_LOG(5, "cluster busy");
+                        scm_request_done(scmrq);
+                        return;
+                }
+                if (scm_need_cluster_request(scmrq)) {
+                        blk_start_request(req);
+                        scm_initiate_cluster_request(scmrq);
+                        return;
+                }
                 scm_request_prepare(scmrq);
                 blk_start_request(req);
 
@@ -282,6 +302,13 @@ static void scm_blk_tasklet(struct scm_blk_dev *bdev)
                         spin_lock_irqsave(&bdev->lock, flags);
                         continue;
                 }
+
+                if (scm_test_cluster_request(scmrq)) {
+                        scm_cluster_request_irq(scmrq);
+                        spin_lock_irqsave(&bdev->lock, flags);
+                        continue;
+                }
+
                 scm_request_finish(scmrq);
                 atomic_dec(&bdev->queued_reqs);
                 spin_lock_irqsave(&bdev->lock, flags);
@@ -325,6 +352,7 @@ int scm_blk_dev_setup(struct scm_blk_dev *bdev, struct scm_device *scmdev)
         blk_queue_max_hw_sectors(rq, nr_max_blk << 3); /* 8 * 512 = blk_size */
         blk_queue_max_segments(rq, nr_max_blk);
         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, rq);
+        scm_blk_dev_cluster_setup(bdev);
 
         bdev->gendisk = alloc_disk(SCM_NR_PARTS);
         if (!bdev->gendisk)
@@ -370,7 +398,10 @@ void scm_blk_dev_cleanup(struct scm_blk_dev *bdev)
 
 static int __init scm_blk_init(void)
 {
-        int ret;
+        int ret = -EINVAL;
+
+        if (!scm_cluster_size_valid())
+                goto out;
 
         ret = register_blkdev(0, "scm");
         if (ret < 0)
diff --git a/drivers/s390/block/scm_blk.h b/drivers/s390/block/scm_blk.h
index 5aba5612588f..7ac6bad919ef 100644
--- a/drivers/s390/block/scm_blk.h
+++ b/drivers/s390/block/scm_blk.h
@@ -22,6 +22,9 @@ struct scm_blk_dev {
         spinlock_t lock;        /* guard the rest of the blockdev */
         atomic_t queued_reqs;
         struct list_head finished_requests;
+#ifdef CONFIG_SCM_BLOCK_CLUSTER_WRITE
+        struct list_head cluster_list;
+#endif
 };
 
 struct scm_request {
@@ -32,6 +35,13 @@ struct scm_request {
         struct list_head list;
         u8 retries;
         int error;
+#ifdef CONFIG_SCM_BLOCK_CLUSTER_WRITE
+        struct {
+                enum {CLUSTER_NONE, CLUSTER_READ, CLUSTER_WRITE} state;
+                struct list_head list;
+                void **buf;
+        } cluster;
+#endif
 };
 
 #define to_aobrq(rq) container_of((void *) rq, struct aob_rq_header, data)
@@ -40,9 +50,37 @@ int scm_blk_dev_setup(struct scm_blk_dev *, struct scm_device *);
 void scm_blk_dev_cleanup(struct scm_blk_dev *);
 void scm_blk_irq(struct scm_device *, void *, int);
 
+void scm_request_finish(struct scm_request *);
+void scm_request_requeue(struct scm_request *);
+
 int scm_drv_init(void);
 void scm_drv_cleanup(void);
 
+#ifdef CONFIG_SCM_BLOCK_CLUSTER_WRITE
+void __scm_free_rq_cluster(struct scm_request *);
+int __scm_alloc_rq_cluster(struct scm_request *);
+void scm_request_cluster_init(struct scm_request *);
+bool scm_reserve_cluster(struct scm_request *);
+void scm_release_cluster(struct scm_request *);
+void scm_blk_dev_cluster_setup(struct scm_blk_dev *);
+bool scm_need_cluster_request(struct scm_request *);
+void scm_initiate_cluster_request(struct scm_request *);
+void scm_cluster_request_irq(struct scm_request *);
+bool scm_test_cluster_request(struct scm_request *);
+bool scm_cluster_size_valid(void);
+#else
+#define __scm_free_rq_cluster(scmrq) {}
+#define __scm_alloc_rq_cluster(scmrq) 0
+#define scm_request_cluster_init(scmrq) {}
+#define scm_reserve_cluster(scmrq) true
+#define scm_release_cluster(scmrq) {}
+#define scm_blk_dev_cluster_setup(bdev) {}
+#define scm_need_cluster_request(scmrq) false
+#define scm_initiate_cluster_request(scmrq) {}
+#define scm_cluster_request_irq(scmrq) {}
+#define scm_test_cluster_request(scmrq) false
+#define scm_cluster_size_valid() true
+#endif
 
 extern debug_info_t *scm_debug;
 
diff --git a/drivers/s390/block/scm_blk_cluster.c b/drivers/s390/block/scm_blk_cluster.c
new file mode 100644
index 000000000000..f4bb61b0cea1
--- /dev/null
+++ b/drivers/s390/block/scm_blk_cluster.c
@@ -0,0 +1,228 @@
+/*
+ * Block driver for s390 storage class memory.
+ *
+ * Copyright IBM Corp. 2012
+ * Author(s): Sebastian Ott <sebott@linux.vnet.ibm.com>
+ */
+
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/blkdev.h>
+#include <linux/genhd.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <asm/eadm.h>
+#include "scm_blk.h"
+
+static unsigned int write_cluster_size = 64;
+module_param(write_cluster_size, uint, S_IRUGO);
+MODULE_PARM_DESC(write_cluster_size,
+                 "Number of pages used for contiguous writes.");
+
+#define CLUSTER_SIZE (write_cluster_size * PAGE_SIZE)
+
+void __scm_free_rq_cluster(struct scm_request *scmrq)
+{
+        int i;
+
+        if (!scmrq->cluster.buf)
+                return;
+
+        for (i = 0; i < 2 * write_cluster_size; i++)
+                free_page((unsigned long) scmrq->cluster.buf[i]);
+
+        kfree(scmrq->cluster.buf);
+}
+
+int __scm_alloc_rq_cluster(struct scm_request *scmrq)
+{
+        int i;
+
+        scmrq->cluster.buf = kzalloc(sizeof(void *) * 2 * write_cluster_size,
+                                 GFP_KERNEL);
+        if (!scmrq->cluster.buf)
+                return -ENOMEM;
+
+        for (i = 0; i < 2 * write_cluster_size; i++) {
+                scmrq->cluster.buf[i] = (void *) get_zeroed_page(GFP_DMA);
+                if (!scmrq->cluster.buf[i])
+                        return -ENOMEM;
+        }
+        INIT_LIST_HEAD(&scmrq->cluster.list);
+        return 0;
+}
+
+void scm_request_cluster_init(struct scm_request *scmrq)
+{
+        scmrq->cluster.state = CLUSTER_NONE;
+}
+
+static bool clusters_intersect(struct scm_request *A, struct scm_request *B)
+{
+        unsigned long firstA, lastA, firstB, lastB;
+
+        firstA = ((u64) blk_rq_pos(A->request) << 9) / CLUSTER_SIZE;
+        lastA = (((u64) blk_rq_pos(A->request) << 9) +
+                    blk_rq_bytes(A->request) - 1) / CLUSTER_SIZE;
+
+        firstB = ((u64) blk_rq_pos(B->request) << 9) / CLUSTER_SIZE;
+        lastB = (((u64) blk_rq_pos(B->request) << 9) +
+                    blk_rq_bytes(B->request) - 1) / CLUSTER_SIZE;
+
+        return (firstB <= lastA && firstA <= lastB);
+}
+
+bool scm_reserve_cluster(struct scm_request *scmrq)
+{
+        struct scm_blk_dev *bdev = scmrq->bdev;
+        struct scm_request *iter;
+
+        if (write_cluster_size == 0)
+                return true;
+
+        spin_lock(&bdev->lock);
+        list_for_each_entry(iter, &bdev->cluster_list, cluster.list) {
+                if (clusters_intersect(scmrq, iter) &&
+                    (rq_data_dir(scmrq->request) == WRITE ||
+                     rq_data_dir(iter->request) == WRITE)) {
+                        spin_unlock(&bdev->lock);
+                        return false;
+                }
+        }
+        list_add(&scmrq->cluster.list, &bdev->cluster_list);
+        spin_unlock(&bdev->lock);
+
+        return true;
+}
+
+void scm_release_cluster(struct scm_request *scmrq)
+{
+        struct scm_blk_dev *bdev = scmrq->bdev;
+        unsigned long flags;
+
+        if (write_cluster_size == 0)
+                return;
+
+        spin_lock_irqsave(&bdev->lock, flags);
+        list_del(&scmrq->cluster.list);
+        spin_unlock_irqrestore(&bdev->lock, flags);
+}
+
+void scm_blk_dev_cluster_setup(struct scm_blk_dev *bdev)
+{
+        INIT_LIST_HEAD(&bdev->cluster_list);
+        blk_queue_io_opt(bdev->rq, CLUSTER_SIZE);
+}
+
+static void scm_prepare_cluster_request(struct scm_request *scmrq)
+{
+        struct scm_blk_dev *bdev = scmrq->bdev;
+        struct scm_device *scmdev = bdev->gendisk->private_data;
+        struct request *req = scmrq->request;
+        struct aidaw *aidaw = scmrq->aidaw;
+        struct msb *msb = &scmrq->aob->msb[0];
+        struct req_iterator iter;
+        struct bio_vec *bv;
+        int i = 0;
+        u64 addr;
+
+        switch (scmrq->cluster.state) {
+        case CLUSTER_NONE:
+                scmrq->cluster.state = CLUSTER_READ;
+                /* fall through */
+        case CLUSTER_READ:
+                scmrq->aob->request.msb_count = 1;
+                msb->bs = MSB_BS_4K;
+                msb->oc = MSB_OC_READ;
+                msb->flags = MSB_FLAG_IDA;
+                msb->data_addr = (u64) aidaw;
+                msb->blk_count = write_cluster_size;
+
+                addr = scmdev->address + ((u64) blk_rq_pos(req) << 9);
+                msb->scm_addr = round_down(addr, CLUSTER_SIZE);
+
+                if (msb->scm_addr !=
+                    round_down(addr + (u64) blk_rq_bytes(req) - 1,
+                               CLUSTER_SIZE))
+                        msb->blk_count = 2 * write_cluster_size;
+
+                for (i = 0; i < msb->blk_count; i++) {
+                        aidaw->data_addr = (u64) scmrq->cluster.buf[i];
+                        aidaw++;
+                }
+
+                break;
+        case CLUSTER_WRITE:
+                msb->oc = MSB_OC_WRITE;
+
+                for (addr = msb->scm_addr;
+                     addr < scmdev->address + ((u64) blk_rq_pos(req) << 9);
+                     addr += PAGE_SIZE) {
+                        aidaw->data_addr = (u64) scmrq->cluster.buf[i];
+                        aidaw++;
+                        i++;
+                }
+                rq_for_each_segment(bv, req, iter) {
+                        aidaw->data_addr = (u64) page_address(bv->bv_page);
+                        aidaw++;
+                        i++;
+                }
+                for (; i < msb->blk_count; i++) {
+                        aidaw->data_addr = (u64) scmrq->cluster.buf[i];
+                        aidaw++;
+                }
+                break;
+        }
+}
+
+bool scm_need_cluster_request(struct scm_request *scmrq)
+{
+        if (rq_data_dir(scmrq->request) == READ)
+                return false;
+
+        return blk_rq_bytes(scmrq->request) < CLUSTER_SIZE;
+}
+
+/* Called with queue lock held. */
+void scm_initiate_cluster_request(struct scm_request *scmrq)
+{
+        scm_prepare_cluster_request(scmrq);
+        if (scm_start_aob(scmrq->aob))
+                scm_request_requeue(scmrq);
+}
+
+bool scm_test_cluster_request(struct scm_request *scmrq)
+{
+        return scmrq->cluster.state != CLUSTER_NONE;
+}
+
+void scm_cluster_request_irq(struct scm_request *scmrq)
+{
+        struct scm_blk_dev *bdev = scmrq->bdev;
+        unsigned long flags;
+
+        switch (scmrq->cluster.state) {
+        case CLUSTER_NONE:
+                BUG();
+                break;
+        case CLUSTER_READ:
+                if (scmrq->error) {
+                        scm_request_finish(scmrq);
+                        break;
+                }
+                scmrq->cluster.state = CLUSTER_WRITE;
+                spin_lock_irqsave(&bdev->rq_lock, flags);
+                scm_initiate_cluster_request(scmrq);
+                spin_unlock_irqrestore(&bdev->rq_lock, flags);
+                break;
+        case CLUSTER_WRITE:
+                scm_request_finish(scmrq);
+                break;
+        }
+}
+
+bool scm_cluster_size_valid(void)
+{
+        return write_cluster_size == 0 || write_cluster_size == 32 ||
+                write_cluster_size == 64 || write_cluster_size == 128;
+}