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SubjectRe: [PATCH 2/2] pmem: add a driver for persistent memory
On 04/01/2015 10:12 AM, Christoph Hellwig wrote:
> 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);

OK cool I was afraid since you did not like my unlikely patch
that you might have missed this fix.

> + 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);

You might as well rw & WRITE also for the above pmem_do_bvec call.
If there can be such problem than the rw == READ inside
pmem_do_bvec will fail as well.

> + 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;

You have removed the pmem_mapmem() helper and embedded all this here.
The patch to add page-structs that I'm posting on top of
this, uses the abstraction to switch between implementations.

I'll add the split-out to the page-structs patch.

Am heavy testing this set (Together with my small fix to e820)
And will report tomorrow if the lab is able to survive the night.

Thanks
Boaz

> +
> + 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);
>



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