lguest: the block driver
Lguest block driver A simple block driver for lguest. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Andi Kleen <ak@suse.de> Cc: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rusty Russell
Linus Torvalds
parent
d503e2fa5a
commit
b754416bfe
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@ -30,3 +30,4 @@ obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
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obj-$(CONFIG_BLK_DEV_UB) += ub.o
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obj-$(CONFIG_BLK_DEV_UB) += ub.o
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obj-$(CONFIG_XEN_BLKDEV_FRONTEND) += xen-blkfront.o
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obj-$(CONFIG_XEN_BLKDEV_FRONTEND) += xen-blkfront.o
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obj-$(CONFIG_LGUEST_GUEST) += lguest_blk.o
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@ -0,0 +1,275 @@
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/* A simple block driver for lguest.
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*
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* Copyright 2006 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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//#define DEBUG
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#include <linux/init.h>
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#include <linux/types.h>
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#include <linux/blkdev.h>
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#include <linux/interrupt.h>
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#include <linux/lguest_bus.h>
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static char next_block_index = 'a';
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struct blockdev
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{
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spinlock_t lock;
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/* The disk structure for the kernel. */
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struct gendisk *disk;
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/* The major number for this disk. */
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int major;
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int irq;
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unsigned long phys_addr;
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/* The mapped block page. */
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struct lguest_block_page *lb_page;
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/* We only have a single request outstanding at a time. */
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struct lguest_dma dma;
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struct request *req;
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};
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/* Jens gave me this nice helper to end all chunks of a request. */
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static void end_entire_request(struct request *req, int uptodate)
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{
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if (end_that_request_first(req, uptodate, req->hard_nr_sectors))
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BUG();
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add_disk_randomness(req->rq_disk);
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blkdev_dequeue_request(req);
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end_that_request_last(req, uptodate);
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}
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static irqreturn_t lgb_irq(int irq, void *_bd)
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{
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struct blockdev *bd = _bd;
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unsigned long flags;
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if (!bd->req) {
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pr_debug("No work!\n");
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return IRQ_NONE;
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}
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if (!bd->lb_page->result) {
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pr_debug("No result!\n");
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return IRQ_NONE;
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}
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spin_lock_irqsave(&bd->lock, flags);
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end_entire_request(bd->req, bd->lb_page->result == 1);
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bd->req = NULL;
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bd->dma.used_len = 0;
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blk_start_queue(bd->disk->queue);
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spin_unlock_irqrestore(&bd->lock, flags);
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return IRQ_HANDLED;
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}
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static unsigned int req_to_dma(struct request *req, struct lguest_dma *dma)
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{
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unsigned int i = 0, idx, len = 0;
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struct bio *bio;
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rq_for_each_bio(bio, req) {
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struct bio_vec *bvec;
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bio_for_each_segment(bvec, bio, idx) {
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BUG_ON(i == LGUEST_MAX_DMA_SECTIONS);
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BUG_ON(!bvec->bv_len);
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dma->addr[i] = page_to_phys(bvec->bv_page)
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+ bvec->bv_offset;
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dma->len[i] = bvec->bv_len;
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len += bvec->bv_len;
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i++;
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}
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}
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if (i < LGUEST_MAX_DMA_SECTIONS)
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dma->len[i] = 0;
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return len;
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}
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static void empty_dma(struct lguest_dma *dma)
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{
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dma->len[0] = 0;
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}
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static void setup_req(struct blockdev *bd,
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int type, struct request *req, struct lguest_dma *dma)
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{
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bd->lb_page->type = type;
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bd->lb_page->sector = req->sector;
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bd->lb_page->result = 0;
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bd->req = req;
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bd->lb_page->bytes = req_to_dma(req, dma);
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}
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static void do_write(struct blockdev *bd, struct request *req)
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{
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struct lguest_dma send;
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pr_debug("lgb: WRITE sector %li\n", (long)req->sector);
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setup_req(bd, 1, req, &send);
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lguest_send_dma(bd->phys_addr, &send);
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}
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static void do_read(struct blockdev *bd, struct request *req)
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{
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struct lguest_dma ping;
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pr_debug("lgb: READ sector %li\n", (long)req->sector);
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setup_req(bd, 0, req, &bd->dma);
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empty_dma(&ping);
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lguest_send_dma(bd->phys_addr, &ping);
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}
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static void do_lgb_request(request_queue_t *q)
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{
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struct blockdev *bd;
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struct request *req;
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again:
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req = elv_next_request(q);
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if (!req)
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return;
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bd = req->rq_disk->private_data;
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/* Sometimes we get repeated requests after blk_stop_queue. */
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if (bd->req)
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return;
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if (!blk_fs_request(req)) {
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pr_debug("Got non-command 0x%08x\n", req->cmd_type);
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req->errors++;
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end_entire_request(req, 0);
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goto again;
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}
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if (rq_data_dir(req) == WRITE)
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do_write(bd, req);
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else
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do_read(bd, req);
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/* Wait for interrupt to tell us it's done. */
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blk_stop_queue(q);
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}
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static struct block_device_operations lguestblk_fops = {
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.owner = THIS_MODULE,
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};
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static int lguestblk_probe(struct lguest_device *lgdev)
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{
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struct blockdev *bd;
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int err;
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int irqflags = IRQF_SHARED;
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bd = kmalloc(sizeof(*bd), GFP_KERNEL);
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if (!bd)
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return -ENOMEM;
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spin_lock_init(&bd->lock);
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bd->irq = lgdev_irq(lgdev);
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bd->req = NULL;
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bd->dma.used_len = 0;
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bd->dma.len[0] = 0;
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bd->phys_addr = (lguest_devices[lgdev->index].pfn << PAGE_SHIFT);
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bd->lb_page = lguest_map(bd->phys_addr, 1);
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if (!bd->lb_page) {
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err = -ENOMEM;
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goto out_free_bd;
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}
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bd->major = register_blkdev(0, "lguestblk");
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if (bd->major < 0) {
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err = bd->major;
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goto out_unmap;
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}
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bd->disk = alloc_disk(1);
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if (!bd->disk) {
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err = -ENOMEM;
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goto out_unregister_blkdev;
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}
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bd->disk->queue = blk_init_queue(do_lgb_request, &bd->lock);
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if (!bd->disk->queue) {
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err = -ENOMEM;
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goto out_put_disk;
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}
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/* We can only handle a certain number of sg entries */
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blk_queue_max_hw_segments(bd->disk->queue, LGUEST_MAX_DMA_SECTIONS);
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/* Buffers must not cross page boundaries */
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blk_queue_segment_boundary(bd->disk->queue, PAGE_SIZE-1);
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sprintf(bd->disk->disk_name, "lgb%c", next_block_index++);
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if (lguest_devices[lgdev->index].features & LGUEST_DEVICE_F_RANDOMNESS)
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irqflags |= IRQF_SAMPLE_RANDOM;
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err = request_irq(bd->irq, lgb_irq, irqflags, bd->disk->disk_name, bd);
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if (err)
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goto out_cleanup_queue;
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err = lguest_bind_dma(bd->phys_addr, &bd->dma, 1, bd->irq);
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if (err)
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goto out_free_irq;
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bd->disk->major = bd->major;
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bd->disk->first_minor = 0;
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bd->disk->private_data = bd;
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bd->disk->fops = &lguestblk_fops;
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/* This is initialized to the disk size by the other end. */
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set_capacity(bd->disk, bd->lb_page->num_sectors);
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add_disk(bd->disk);
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printk(KERN_INFO "%s: device %i at major %d\n",
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bd->disk->disk_name, lgdev->index, bd->major);
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lgdev->private = bd;
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return 0;
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out_free_irq:
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free_irq(bd->irq, bd);
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out_cleanup_queue:
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blk_cleanup_queue(bd->disk->queue);
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out_put_disk:
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put_disk(bd->disk);
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out_unregister_blkdev:
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unregister_blkdev(bd->major, "lguestblk");
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out_unmap:
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lguest_unmap(bd->lb_page);
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out_free_bd:
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kfree(bd);
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return err;
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}
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static struct lguest_driver lguestblk_drv = {
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.name = "lguestblk",
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.owner = THIS_MODULE,
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.device_type = LGUEST_DEVICE_T_BLOCK,
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.probe = lguestblk_probe,
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};
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static __init int lguestblk_init(void)
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{
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return register_lguest_driver(&lguestblk_drv);
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}
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module_init(lguestblk_init);
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MODULE_DESCRIPTION("Lguest block driver");
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MODULE_LICENSE("GPL");
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