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Subject[PATCH 2/2] pmem: add a driver for persistent memory
Date
From: Ross Zwisler <ross.zwisler@linux.intel.com>

PMEM is a new driver that presents a reserved range of memory as a
block device. This is useful for developing with NV-DIMMs, and
can be used with volatile memory as a development platform.

This patch contains the initial driver from Ross Zwisler, with
various changes from Boaz Harrosh and me.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
[hch: convert to use a platform_device for discovery, fix partition
support, merged various patches from Boaz]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
---
MAINTAINERS | 6 ++
drivers/block/Kconfig | 11 +++
drivers/block/Makefile | 1 +
drivers/block/pmem.c | 260 +++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 278 insertions(+)
create mode 100644 drivers/block/pmem.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 1de6afa..4517613 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8071,6 +8071,12 @@ S: Maintained
F: Documentation/blockdev/ramdisk.txt
F: drivers/block/brd.c

+PERSISTENT MEMORY DRIVER
+M: Ross Zwisler <ross.zwisler@linux.intel.com>
+L: linux-nvdimm@lists.01.org
+S: Supported
+F: drivers/block/pmem.c
+
RANDOM NUMBER DRIVER
M: "Theodore Ts'o" <tytso@mit.edu>
S: Maintained
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 1b8094d..34753cf 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -404,6 +404,17 @@ config BLK_DEV_RAM_DAX
and will prevent RAM block device backing store memory from being
allocated from highmem (only a problem for highmem systems).

+config BLK_DEV_PMEM
+ tristate "Persistent memory block device support"
+ help
+ Saying Y here will allow you to use a contiguous range of reserved
+ memory as one or more block devices.
+
+ To compile this driver as a module, choose M here: the module will be
+ called pmem.
+
+ If unsure, say N.
+
config CDROM_PKTCDVD
tristate "Packet writing on CD/DVD media"
depends on !UML
diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index 02b688d..9cc6c18 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_PS3_VRAM) += ps3vram.o
obj-$(CONFIG_ATARI_FLOPPY) += ataflop.o
obj-$(CONFIG_AMIGA_Z2RAM) += z2ram.o
obj-$(CONFIG_BLK_DEV_RAM) += brd.o
+obj-$(CONFIG_BLK_DEV_PMEM) += pmem.o
obj-$(CONFIG_BLK_DEV_LOOP) += loop.o
obj-$(CONFIG_BLK_CPQ_DA) += cpqarray.o
obj-$(CONFIG_BLK_CPQ_CISS_DA) += cciss.o
diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
new file mode 100644
index 0000000..0232ab7
--- /dev/null
+++ b/drivers/block/pmem.c
@@ -0,0 +1,260 @@
+/*
+ * Persistent Memory Driver
+ * Copyright (c) 2014, Intel Corporation.
+ * Copyright (c) 2015, Christoph Hellwig <hch@lst.de>.
+ * Copyright (c) 2015, Boaz Harrosh <boaz@plexistor.com>.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ */
+
+#include <asm/cacheflush.h>
+#include <linux/blkdev.h>
+#include <linux/hdreg.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+
+#define PMEM_MINORS 16
+
+struct pmem_device {
+ struct request_queue *pmem_queue;
+ struct gendisk *pmem_disk;
+
+ /* One contiguous memory region per device */
+ phys_addr_t phys_addr;
+ void *virt_addr;
+ size_t size;
+};
+
+static int pmem_major;
+static atomic_t pmem_index;
+
+static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
+ unsigned int len, unsigned int off, int rw,
+ sector_t sector)
+{
+ void *mem = kmap_atomic(page);
+ size_t pmem_off = sector << 9;
+
+ if (rw == READ) {
+ memcpy(mem + off, pmem->virt_addr + pmem_off, len);
+ flush_dcache_page(page);
+ } else {
+ flush_dcache_page(page);
+ memcpy(pmem->virt_addr + pmem_off, mem + off, len);
+ }
+
+ kunmap_atomic(mem);
+}
+
+static void pmem_make_request(struct request_queue *q, struct bio *bio)
+{
+ struct block_device *bdev = bio->bi_bdev;
+ struct pmem_device *pmem = bdev->bd_disk->private_data;
+ int rw;
+ struct bio_vec bvec;
+ sector_t sector;
+ struct bvec_iter iter;
+ int err = 0;
+
+ if (bio_end_sector(bio) > get_capacity(bdev->bd_disk)) {
+ err = -EIO;
+ goto out;
+ }
+
+ BUG_ON(bio->bi_rw & REQ_DISCARD);
+
+ rw = bio_data_dir(bio);
+ sector = bio->bi_iter.bi_sector;
+ bio_for_each_segment(bvec, bio, iter) {
+ pmem_do_bvec(pmem, bvec.bv_page, bvec.bv_len, bvec.bv_offset,
+ rw, sector);
+ sector += bvec.bv_len >> 9;
+ }
+
+out:
+ bio_endio(bio, err);
+}
+
+static int pmem_rw_page(struct block_device *bdev, sector_t sector,
+ struct page *page, int rw)
+{
+ struct pmem_device *pmem = bdev->bd_disk->private_data;
+
+ pmem_do_bvec(pmem, page, PAGE_CACHE_SIZE, 0, rw, sector);
+ page_endio(page, rw & WRITE, 0);
+ return 0;
+}
+
+static long pmem_direct_access(struct block_device *bdev, sector_t sector,
+ void **kaddr, unsigned long *pfn, long size)
+{
+ struct pmem_device *pmem = bdev->bd_disk->private_data;
+ size_t offset = sector << 9;
+
+ if (!pmem)
+ return -ENODEV;
+
+ *kaddr = pmem->virt_addr + offset;
+ *pfn = (pmem->phys_addr + offset) >> PAGE_SHIFT;
+
+ return pmem->size - offset;
+}
+
+static const struct block_device_operations pmem_fops = {
+ .owner = THIS_MODULE,
+ .rw_page = pmem_rw_page,
+ .direct_access = pmem_direct_access,
+};
+
+static struct pmem_device *pmem_alloc(struct device *dev, struct resource *res)
+{
+ struct pmem_device *pmem;
+ struct gendisk *disk;
+ int idx, err;
+
+ err = -ENOMEM;
+ pmem = kzalloc(sizeof(*pmem), GFP_KERNEL);
+ if (!pmem)
+ goto out;
+
+ pmem->phys_addr = res->start;
+ pmem->size = resource_size(res);
+
+ err = -EINVAL;
+ if (!request_mem_region(pmem->phys_addr, pmem->size, "pmem")) {
+ dev_warn(dev, "could not reserve region [0x%llx:0x%zx]\n",
+ pmem->phys_addr, pmem->size);
+ goto out_free_dev;
+ }
+
+ /*
+ * Map the memory as non-cachable, as we can't write back the contents
+ * of the CPU caches in case of a crash.
+ */
+ err = -ENOMEM;
+ pmem->virt_addr = ioremap_nocache(pmem->phys_addr, pmem->size);
+ if (!pmem->virt_addr)
+ goto out_release_region;
+
+ pmem->pmem_queue = blk_alloc_queue(GFP_KERNEL);
+ if (!pmem->pmem_queue)
+ goto out_unmap;
+
+ blk_queue_make_request(pmem->pmem_queue, pmem_make_request);
+ blk_queue_max_hw_sectors(pmem->pmem_queue, 1024);
+ blk_queue_bounce_limit(pmem->pmem_queue, BLK_BOUNCE_ANY);
+
+ disk = alloc_disk(PMEM_MINORS);
+ if (!disk)
+ goto out_free_queue;
+
+ idx = atomic_inc_return(&pmem_index) - 1;
+
+ disk->major = pmem_major;
+ disk->first_minor = PMEM_MINORS * idx;
+ disk->fops = &pmem_fops;
+ disk->private_data = pmem;
+ disk->queue = pmem->pmem_queue;
+ disk->flags = GENHD_FL_EXT_DEVT;
+ sprintf(disk->disk_name, "pmem%d", idx);
+ disk->driverfs_dev = dev;
+ set_capacity(disk, pmem->size >> 9);
+ pmem->pmem_disk = disk;
+
+ add_disk(disk);
+ return pmem;
+
+out_free_queue:
+ blk_cleanup_queue(pmem->pmem_queue);
+out_unmap:
+ iounmap(pmem->virt_addr);
+out_release_region:
+ release_mem_region(pmem->phys_addr, pmem->size);
+out_free_dev:
+ kfree(pmem);
+out:
+ return ERR_PTR(err);
+}
+
+static void pmem_free(struct pmem_device *pmem)
+{
+ del_gendisk(pmem->pmem_disk);
+ put_disk(pmem->pmem_disk);
+ blk_cleanup_queue(pmem->pmem_queue);
+ iounmap(pmem->virt_addr);
+ release_mem_region(pmem->phys_addr, pmem->size);
+ kfree(pmem);
+}
+
+static int pmem_probe(struct platform_device *pdev)
+{
+ struct pmem_device *pmem;
+ struct resource *res;
+
+ if (WARN_ON(pdev->num_resources > 1))
+ return -ENXIO;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res)
+ return -ENXIO;
+
+ pmem = pmem_alloc(&pdev->dev, res);
+ if (IS_ERR(pmem))
+ return PTR_ERR(pmem);
+
+ platform_set_drvdata(pdev, pmem);
+ return 0;
+}
+
+static int pmem_remove(struct platform_device *pdev)
+{
+ struct pmem_device *pmem = platform_get_drvdata(pdev);
+
+ pmem_free(pmem);
+ return 0;
+}
+
+static struct platform_driver pmem_driver = {
+ .probe = pmem_probe,
+ .remove = pmem_remove,
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "pmem",
+ },
+};
+
+static int __init pmem_init(void)
+{
+ int error;
+
+ pmem_major = register_blkdev(0, "pmem");
+ if (pmem_major < 0)
+ return pmem_major;
+
+ error = platform_driver_register(&pmem_driver);
+ if (error)
+ unregister_blkdev(pmem_major, "pmem");
+ return error;
+}
+
+static void pmem_exit(void)
+{
+ platform_driver_unregister(&pmem_driver);
+ unregister_blkdev(pmem_major, "pmem");
+}
+
+MODULE_AUTHOR("Ross Zwisler <ross.zwisler@linux.intel.com>");
+MODULE_LICENSE("GPL v2");
+
+module_init(pmem_init);
+module_exit(pmem_exit);
--
1.9.1


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