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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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