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5212e11fde
BTT stands for Block Translation Table, and is a way to provide power fail sector atomicity semantics for block devices that have the ability to perform byte granularity IO. It relies on the capability of libnvdimm namespace devices to do byte aligned IO. The BTT works as a stacked blocked device, and reserves a chunk of space from the backing device for its accounting metadata. It is a bio-based driver because all IO is done synchronously, and there is no queuing or asynchronous completions at either the device or the driver level. The BTT uses 'lanes' to index into various 'on-disk' data structures, and lanes also act as a synchronization mechanism in case there are more CPUs than available lanes. We did a comparison between two lane lock strategies - first where we kept an atomic counter around that tracked which was the last lane that was used, and 'our' lane was determined by atomically incrementing that. That way, for the nr_cpus > nr_lanes case, theoretically, no CPU would be blocked waiting for a lane. The other strategy was to use the cpu number we're scheduled on to and hash it to a lane number. Theoretically, this could block an IO that could've otherwise run using a different, free lane. But some fio workloads showed that the direct cpu -> lane hash performed faster than tracking 'last lane' - my reasoning is the cache thrash caused by moving the atomic variable made that approach slower than simply waiting out the in-progress IO. This supports the conclusion that the driver can be a very simple bio-based one that does synchronous IOs instead of queuing. Cc: Andy Lutomirski <luto@amacapital.net> Cc: Boaz Harrosh <boaz@plexistor.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jens Axboe <axboe@fb.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Neil Brown <neilb@suse.de> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Greg KH <gregkh@linuxfoundation.org> [jmoyer: fix nmi watchdog timeout in btt_map_init] [jmoyer: move btt initialization to module load path] [jmoyer: fix memory leak in the btt initialization path] [jmoyer: Don't overwrite corrupted arenas] Signed-off-by: Vishal Verma <vishal.l.verma@linux.intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
303 lines
7.0 KiB
C
303 lines
7.0 KiB
C
/*
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* Persistent Memory Driver
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*
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* Copyright (c) 2014-2015, Intel Corporation.
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* Copyright (c) 2015, Christoph Hellwig <hch@lst.de>.
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* Copyright (c) 2015, Boaz Harrosh <boaz@plexistor.com>.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*/
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#include <asm/cacheflush.h>
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#include <linux/blkdev.h>
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#include <linux/hdreg.h>
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#include <linux/init.h>
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#include <linux/platform_device.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/slab.h>
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#include <linux/nd.h>
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#include "nd.h"
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struct pmem_device {
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struct request_queue *pmem_queue;
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struct gendisk *pmem_disk;
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/* One contiguous memory region per device */
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phys_addr_t phys_addr;
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void *virt_addr;
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size_t size;
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};
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static int pmem_major;
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static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
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unsigned int len, unsigned int off, int rw,
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sector_t sector)
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{
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void *mem = kmap_atomic(page);
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size_t pmem_off = sector << 9;
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if (rw == READ) {
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memcpy(mem + off, pmem->virt_addr + pmem_off, len);
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flush_dcache_page(page);
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} else {
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flush_dcache_page(page);
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memcpy(pmem->virt_addr + pmem_off, mem + off, len);
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}
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kunmap_atomic(mem);
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}
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static void pmem_make_request(struct request_queue *q, struct bio *bio)
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{
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struct block_device *bdev = bio->bi_bdev;
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struct pmem_device *pmem = bdev->bd_disk->private_data;
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int rw;
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struct bio_vec bvec;
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sector_t sector;
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struct bvec_iter iter;
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int err = 0;
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if (bio_end_sector(bio) > get_capacity(bdev->bd_disk)) {
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err = -EIO;
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goto out;
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}
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BUG_ON(bio->bi_rw & REQ_DISCARD);
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rw = bio_data_dir(bio);
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sector = bio->bi_iter.bi_sector;
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bio_for_each_segment(bvec, bio, iter) {
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pmem_do_bvec(pmem, bvec.bv_page, bvec.bv_len, bvec.bv_offset,
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rw, sector);
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sector += bvec.bv_len >> 9;
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}
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out:
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bio_endio(bio, err);
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}
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static int pmem_rw_page(struct block_device *bdev, sector_t sector,
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struct page *page, int rw)
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{
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struct pmem_device *pmem = bdev->bd_disk->private_data;
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pmem_do_bvec(pmem, page, PAGE_CACHE_SIZE, 0, rw, sector);
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page_endio(page, rw & WRITE, 0);
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return 0;
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}
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static long pmem_direct_access(struct block_device *bdev, sector_t sector,
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void **kaddr, unsigned long *pfn, long size)
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{
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struct pmem_device *pmem = bdev->bd_disk->private_data;
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size_t offset = sector << 9;
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if (!pmem)
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return -ENODEV;
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*kaddr = pmem->virt_addr + offset;
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*pfn = (pmem->phys_addr + offset) >> PAGE_SHIFT;
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return pmem->size - offset;
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}
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static const struct block_device_operations pmem_fops = {
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.owner = THIS_MODULE,
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.rw_page = pmem_rw_page,
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.direct_access = pmem_direct_access,
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};
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static struct pmem_device *pmem_alloc(struct device *dev,
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struct resource *res, int id)
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{
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struct pmem_device *pmem;
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pmem = kzalloc(sizeof(*pmem), GFP_KERNEL);
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if (!pmem)
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return ERR_PTR(-ENOMEM);
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pmem->phys_addr = res->start;
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pmem->size = resource_size(res);
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if (!request_mem_region(pmem->phys_addr, pmem->size, dev_name(dev))) {
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dev_warn(dev, "could not reserve region [0x%pa:0x%zx]\n",
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&pmem->phys_addr, pmem->size);
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kfree(pmem);
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return ERR_PTR(-EBUSY);
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}
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/*
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* Map the memory as non-cachable, as we can't write back the contents
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* of the CPU caches in case of a crash.
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*/
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pmem->virt_addr = ioremap_nocache(pmem->phys_addr, pmem->size);
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if (!pmem->virt_addr) {
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release_mem_region(pmem->phys_addr, pmem->size);
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kfree(pmem);
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return ERR_PTR(-ENXIO);
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}
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return pmem;
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}
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static void pmem_detach_disk(struct pmem_device *pmem)
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{
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del_gendisk(pmem->pmem_disk);
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put_disk(pmem->pmem_disk);
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blk_cleanup_queue(pmem->pmem_queue);
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}
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static int pmem_attach_disk(struct nd_namespace_common *ndns,
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struct pmem_device *pmem)
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{
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struct gendisk *disk;
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pmem->pmem_queue = blk_alloc_queue(GFP_KERNEL);
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if (!pmem->pmem_queue)
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return -ENOMEM;
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blk_queue_make_request(pmem->pmem_queue, pmem_make_request);
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blk_queue_max_hw_sectors(pmem->pmem_queue, 1024);
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blk_queue_bounce_limit(pmem->pmem_queue, BLK_BOUNCE_ANY);
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disk = alloc_disk(0);
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if (!disk) {
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blk_cleanup_queue(pmem->pmem_queue);
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return -ENOMEM;
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}
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disk->major = pmem_major;
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disk->first_minor = 0;
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disk->fops = &pmem_fops;
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disk->private_data = pmem;
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disk->queue = pmem->pmem_queue;
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disk->flags = GENHD_FL_EXT_DEVT;
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nvdimm_namespace_disk_name(ndns, disk->disk_name);
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disk->driverfs_dev = &ndns->dev;
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set_capacity(disk, pmem->size >> 9);
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pmem->pmem_disk = disk;
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add_disk(disk);
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return 0;
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}
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static int pmem_rw_bytes(struct nd_namespace_common *ndns,
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resource_size_t offset, void *buf, size_t size, int rw)
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{
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struct pmem_device *pmem = dev_get_drvdata(ndns->claim);
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if (unlikely(offset + size > pmem->size)) {
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dev_WARN_ONCE(&ndns->dev, 1, "request out of range\n");
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return -EFAULT;
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}
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if (rw == READ)
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memcpy(buf, pmem->virt_addr + offset, size);
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else
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memcpy(pmem->virt_addr + offset, buf, size);
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return 0;
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}
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static void pmem_free(struct pmem_device *pmem)
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{
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iounmap(pmem->virt_addr);
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release_mem_region(pmem->phys_addr, pmem->size);
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kfree(pmem);
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}
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static int nd_pmem_probe(struct device *dev)
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{
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struct nd_region *nd_region = to_nd_region(dev->parent);
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struct nd_namespace_common *ndns;
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struct nd_namespace_io *nsio;
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struct pmem_device *pmem;
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int rc;
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ndns = nvdimm_namespace_common_probe(dev);
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if (IS_ERR(ndns))
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return PTR_ERR(ndns);
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nsio = to_nd_namespace_io(&ndns->dev);
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pmem = pmem_alloc(dev, &nsio->res, nd_region->id);
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if (IS_ERR(pmem))
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return PTR_ERR(pmem);
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dev_set_drvdata(dev, pmem);
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ndns->rw_bytes = pmem_rw_bytes;
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if (is_nd_btt(dev))
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rc = nvdimm_namespace_attach_btt(ndns);
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else if (nd_btt_probe(ndns, pmem) == 0) {
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/* we'll come back as btt-pmem */
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rc = -ENXIO;
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} else
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rc = pmem_attach_disk(ndns, pmem);
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if (rc)
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pmem_free(pmem);
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return rc;
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}
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static int nd_pmem_remove(struct device *dev)
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{
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struct pmem_device *pmem = dev_get_drvdata(dev);
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if (is_nd_btt(dev))
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nvdimm_namespace_detach_btt(to_nd_btt(dev)->ndns);
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else
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pmem_detach_disk(pmem);
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pmem_free(pmem);
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return 0;
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}
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MODULE_ALIAS("pmem");
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MODULE_ALIAS_ND_DEVICE(ND_DEVICE_NAMESPACE_IO);
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MODULE_ALIAS_ND_DEVICE(ND_DEVICE_NAMESPACE_PMEM);
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static struct nd_device_driver nd_pmem_driver = {
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.probe = nd_pmem_probe,
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.remove = nd_pmem_remove,
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.drv = {
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.name = "nd_pmem",
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},
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.type = ND_DRIVER_NAMESPACE_IO | ND_DRIVER_NAMESPACE_PMEM,
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};
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static int __init pmem_init(void)
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{
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int error;
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pmem_major = register_blkdev(0, "pmem");
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if (pmem_major < 0)
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return pmem_major;
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error = nd_driver_register(&nd_pmem_driver);
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if (error) {
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unregister_blkdev(pmem_major, "pmem");
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return error;
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}
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return 0;
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}
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module_init(pmem_init);
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static void pmem_exit(void)
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{
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driver_unregister(&nd_pmem_driver.drv);
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unregister_blkdev(pmem_major, "pmem");
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}
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module_exit(pmem_exit);
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MODULE_AUTHOR("Ross Zwisler <ross.zwisler@linux.intel.com>");
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MODULE_LICENSE("GPL v2");
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