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jservjserv
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Merge pull request #370 from sysprog21/extended
Add DMA, block, and network driver examples
2 parents aa65a39 + 563b6db commit 10b4869

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Lines changed: 1340 additions & 2 deletions

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‎examples/Makefile‎

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@@ -37,6 +37,9 @@ obj-m += static_key.o
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obj-m += led.o
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obj-m += dht11.o
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obj-m += devicetree.o
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obj-m += dma.o
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obj-m += blkram.o
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obj-m += vnetloop.o
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KDIR ?= /lib/modules/$(shell uname -r)/build
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PWD := $(CURDIR)

‎examples/blkram.c‎

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// SPDX-License-Identifier: GPL-2.0
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/*
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* blkram.c - Tiny RAM-backed block device using blk-mq.
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*
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* Covers Linux 5.10 through 6.17+ by using version guards at the three
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* major block-layer API transitions:
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*
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* 5.10-5.14 alloc_disk() + blk_mq_init_queue() + blk_cleanup_queue()
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* 5.15-6.8 blk_mq_alloc_disk(set, queuedata) [2-arg macro]
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* 6.9+ blk_mq_alloc_disk(set, lim, queuedata) [3-arg macro]
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*
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* Teardown likewise varies: blk_cleanup_queue() was removed in 5.15,
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* blk_cleanup_disk() was removed in 5.18; modern kernels use
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* del_gendisk() + put_disk().
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*/
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#include <linux/blk-mq.h>
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#include <linux/blkdev.h>
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#include <linux/errno.h>
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#include <linux/highmem.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/version.h>
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#include <linux/vmalloc.h>
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/* genhd.h was removed in 5.18; its content lives in blkdev.h since 5.17. */
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#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 18, 0)
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#include <linux/genhd.h>
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#endif
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#define BLKRAM_SECTOR_SIZE 512
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static unsigned long blkram_mb = 8;
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module_param(blkram_mb, ulong, 0444);
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MODULE_PARM_DESC(blkram_mb, "Size of the RAM disk in MiB");
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struct blkram_dev {
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struct blk_mq_tag_set tag_set;
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struct gendisk *disk;
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struct request_queue *queue;
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u8 *data;
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size_t size;
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};
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static struct blkram_dev *blkram;
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static int blkram_major;
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static blk_status_t blkram_transfer(struct blkram_dev *dev, struct request *rq)
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{
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struct req_iterator iter;
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struct bio_vec bvec;
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sector_t sector = blk_rq_pos(rq);
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unsigned long offset = (unsigned long)sector * BLKRAM_SECTOR_SIZE;
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rq_for_each_segment(bvec, rq, iter)
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{
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unsigned int len = bvec.bv_len;
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void *iobuf;
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if (offset + len > dev->size)
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return BLK_STS_IOERR;
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/* kmap_local_page() appeared in 5.11; fall back to kmap_atomic() on 5.10. */
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 11, 0)
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iobuf = kmap_local_page(bvec.bv_page) + bvec.bv_offset;
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#else
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iobuf = kmap_atomic(bvec.bv_page) + bvec.bv_offset;
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#endif
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if (rq_data_dir(rq) == WRITE)
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memcpy(dev->data + offset, iobuf, len);
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else
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memcpy(iobuf, dev->data + offset, len);
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 11, 0)
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kunmap_local(iobuf);
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#else
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kunmap_atomic(iobuf);
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#endif
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offset += len;
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}
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return BLK_STS_OK;
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}
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static blk_status_t blkram_queue_rq(struct blk_mq_hw_ctx *hctx,
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const struct blk_mq_queue_data *bd)
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{
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struct request *rq = bd->rq;
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struct blkram_dev *dev = rq->q->queuedata;
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blk_status_t status;
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blk_mq_start_request(rq);
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if (blk_rq_is_passthrough(rq))
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status = BLK_STS_IOERR;
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else
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status = blkram_transfer(dev, rq);
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blk_mq_end_request(rq, status);
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return BLK_STS_OK;
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}
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static const struct blk_mq_ops blkram_mq_ops = {
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.queue_rq = blkram_queue_rq,
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};
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static const struct block_device_operations blkram_fops = {
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.owner = THIS_MODULE,
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};
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static int __init blkram_init(void)
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{
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unsigned long sectors;
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int ret;
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blkram_major = register_blkdev(0, "blkram");
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if (blkram_major < 0)
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return blkram_major;
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blkram = kzalloc(sizeof(*blkram), GFP_KERNEL);
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if (!blkram) {
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ret = -ENOMEM;
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goto err_unreg;
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}
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blkram->size = blkram_mb * 1024 * 1024;
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sectors = blkram->size / BLKRAM_SECTOR_SIZE;
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blkram->data = vzalloc(blkram->size);
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if (!blkram->data) {
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ret = -ENOMEM;
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goto err_free_dev;
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}
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blkram->tag_set.ops = &blkram_mq_ops;
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blkram->tag_set.nr_hw_queues = 1;
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blkram->tag_set.queue_depth = 64;
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blkram->tag_set.numa_node = NUMA_NO_NODE;
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blkram->tag_set.cmd_size = 0;
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/* BLK_MQ_F_SHOULD_MERGE was removed in 6.6+; merging is always on. */
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#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 6, 0)
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blkram->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
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#else
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blkram->tag_set.flags = 0;
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#endif
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blkram->tag_set.driver_data = blkram;
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ret = blk_mq_alloc_tag_set(&blkram->tag_set);
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if (ret)
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goto err_free_data;
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/* Three eras of block-device creation:
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* 6.9+ blk_mq_alloc_disk(set, lim, queuedata) -- 3-arg form.
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* 5.15-6.8 blk_mq_alloc_disk(set, queuedata) -- 2-arg form.
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* 5.10-5.14 alloc_disk() + blk_mq_init_queue() -- separate objects.
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*/
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 9, 0)
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{
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struct queue_limits lim = {
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.logical_block_size = BLKRAM_SECTOR_SIZE,
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};
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blkram->disk = blk_mq_alloc_disk(&blkram->tag_set, &lim, blkram);
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}
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if (IS_ERR(blkram->disk)) {
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ret = PTR_ERR(blkram->disk);
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goto err_tag_set;
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}
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blkram->queue = blkram->disk->queue;
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#elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 15, 0)
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blkram->disk = blk_mq_alloc_disk(&blkram->tag_set, blkram);
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if (IS_ERR(blkram->disk)) {
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ret = PTR_ERR(blkram->disk);
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goto err_tag_set;
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}
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blkram->queue = blkram->disk->queue;
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#else
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blkram->queue = blk_mq_init_queue(&blkram->tag_set);
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if (IS_ERR(blkram->queue)) {
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ret = PTR_ERR(blkram->queue);
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goto err_tag_set;
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}
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blkram->disk = alloc_disk(1);
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if (!blkram->disk) {
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ret = -ENOMEM;
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goto err_cleanup_queue;
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}
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blkram->disk->queue = blkram->queue;
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#endif
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blkram->queue->queuedata = blkram;
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blkram->disk->major = blkram_major;
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blkram->disk->first_minor = 0;
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blkram->disk->minors = 1;
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blkram->disk->fops = &blkram_fops;
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blkram->disk->private_data = blkram;
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snprintf(blkram->disk->disk_name, DISK_NAME_LEN, "blkram0");
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#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 9, 0)
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blk_queue_logical_block_size(blkram->queue, BLKRAM_SECTOR_SIZE);
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#endif
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set_capacity(blkram->disk, sectors);
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/* add_disk() returns int since 5.16; earlier kernels return void. */
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 16, 0)
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ret = add_disk(blkram->disk);
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if (ret)
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goto err_put_disk;
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#else
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add_disk(blkram->disk);
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#endif
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pr_info("blkram: registered /dev/%s (%lu MiB)\n", blkram->disk->disk_name,
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blkram_mb);
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return 0;
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 16, 0)
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err_put_disk:
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put_disk(blkram->disk);
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#endif
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#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 15, 0)
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err_cleanup_queue:
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blk_cleanup_queue(blkram->queue);
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#endif
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err_tag_set:
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blk_mq_free_tag_set(&blkram->tag_set);
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err_free_data:
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vfree(blkram->data);
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err_free_dev:
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kfree(blkram);
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err_unreg:
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unregister_blkdev(blkram_major, "blkram");
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return ret;
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}
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static void __exit blkram_exit(void)
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{
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del_gendisk(blkram->disk);
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put_disk(blkram->disk);
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#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 15, 0)
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blk_cleanup_queue(blkram->queue);
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#endif
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blk_mq_free_tag_set(&blkram->tag_set);
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vfree(blkram->data);
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kfree(blkram);
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unregister_blkdev(blkram_major, "blkram");
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}
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module_init(blkram_init);
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module_exit(blkram_exit);
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MODULE_DESCRIPTION("LKMPG blk-mq RAM disk example");
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MODULE_LICENSE("GPL");

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