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Subject[PATCH 9/10] lguest: block driver
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A simple block driver for lguest (/dev/lgbX).  Only does one request
at once.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

===================================================================
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -28,4 +28,5 @@ obj-$(CONFIG_VIODASD) += viodasd.o
obj-$(CONFIG_VIODASD) += viodasd.o
obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
obj-$(CONFIG_BLK_DEV_UB) += ub.o
+obj-$(CONFIG_LGUEST_GUEST) += lguest_blk.o

===================================================================
--- /dev/null
+++ b/drivers/block/lguest_blk.c
@@ -0,0 +1,260 @@
+/* A simple block driver for lguest.
+ *
+ * Copyright 2006 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+//#define DEBUG
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/blkdev.h>
+#include <linux/interrupt.h>
+#include <asm/lguest_device.h>
+
+static char next_block_index = 'a';
+
+struct blockdev
+{
+ spinlock_t lock;
+
+ /* The disk structure for the kernel. */
+ struct gendisk *disk;
+
+ /* The major number for this disk. */
+ int major;
+ int irq;
+
+ unsigned long phys_addr;
+ /* The ioremap'ed block page. */
+ struct lguest_block_page *lb_page;
+
+ /* We only have a single request outstanding at a time. */
+ struct lguest_dma dma;
+ struct request *req;
+};
+
+static irqreturn_t lgb_irq(int irq, void *_bd)
+{
+ struct blockdev *bd = _bd;
+ unsigned long flags;
+
+ if (!bd->req) {
+ pr_debug("No work!\n");
+ return IRQ_NONE;
+ }
+
+ if (!bd->lb_page->result) {
+ pr_debug("No result!\n");
+ return IRQ_NONE;
+ }
+
+ spin_lock_irqsave(&bd->lock, flags);
+ end_request(bd->req, bd->lb_page->result == 1);
+ bd->req = NULL;
+ bd->dma.used_len = 0;
+ blk_start_queue(bd->disk->queue);
+ spin_unlock_irqrestore(&bd->lock, flags);
+ return IRQ_HANDLED;
+}
+
+static unsigned int req_to_dma(struct request *req, struct lguest_dma *dma)
+{
+ unsigned int i = 0, idx, len = 0;
+ struct bio *bio;
+
+ rq_for_each_bio(bio, req) {
+ struct bio_vec *bvec;
+ bio_for_each_segment(bvec, bio, idx) {
+ BUG_ON(i == LGUEST_MAX_DMA_SECTIONS);
+ BUG_ON(!bvec->bv_len);
+ dma->addr[i] = page_to_phys(bvec->bv_page)
+ + bvec->bv_offset;
+ dma->len[i] = bvec->bv_len;
+ len += bvec->bv_len;
+ i++;
+ }
+ }
+ if (i < LGUEST_MAX_DMA_SECTIONS)
+ dma->len[i] = 0;
+ return len;
+}
+
+static void empty_dma(struct lguest_dma *dma)
+{
+ dma->len[0] = 0;
+}
+
+static void setup_req(struct blockdev *bd,
+ int type, struct request *req, struct lguest_dma *dma)
+{
+ bd->lb_page->type = type;
+ bd->lb_page->sector = req->sector;
+ bd->lb_page->result = 0;
+ bd->req = req;
+ bd->lb_page->bytes = req_to_dma(req, dma);
+}
+
+static int do_write(struct blockdev *bd, struct request *req)
+{
+ struct lguest_dma send;
+
+ pr_debug("lgb: WRITE sector %li\n", (long)req->sector);
+ setup_req(bd, 1, req, &send);
+
+ hcall(LHCALL_SEND_DMA, bd->phys_addr, __pa(&send), 0);
+ return 1;
+}
+
+static int do_read(struct blockdev *bd, struct request *req)
+{
+ struct lguest_dma ping;
+
+ pr_debug("lgb: READ sector %li\n", (long)req->sector);
+ setup_req(bd, 0, req, &bd->dma);
+
+ empty_dma(&ping);
+ hcall(LHCALL_SEND_DMA,bd->phys_addr,__pa(&ping),0);
+ return 1;
+}
+
+static void do_lgb_request(request_queue_t *q)
+{
+ struct blockdev *bd;
+ struct request *req;
+ int ok;
+
+again:
+ req = elv_next_request(q);
+ if (!req)
+ return;
+
+ bd = req->rq_disk->private_data;
+ /* Sometimes we get repeated requests after blk_stop_queue. */
+ if (bd->req)
+ return;
+
+ if (!blk_fs_request(req)) {
+ pr_debug("Got non-command 0x%08x\n", req->cmd_type);
+ error:
+ req->errors++;
+ end_request(req, 0);
+ goto again;
+ } else {
+ if (rq_data_dir(req) == WRITE)
+ ok = do_write(req->rq_disk->private_data, req);
+ else
+ ok = do_read(req->rq_disk->private_data, req);
+
+ if (!ok)
+ goto error;
+ /* Wait for interrupt to tell us it's done. */
+ blk_stop_queue(q);
+ }
+}
+
+static struct block_device_operations lguestblk_fops = {
+ .owner = THIS_MODULE,
+};
+
+static int lguestblk_probe(struct lguest_device *lhdev)
+{
+ struct blockdev *bd;
+ int err;
+ int irqflags = IRQF_SHARED;
+
+ bd = kmalloc(sizeof(*bd), GFP_KERNEL);
+ if (!bd)
+ return -ENOMEM;
+
+ spin_lock_init(&bd->lock);
+ bd->phys_addr = (lguest_devices[lhdev->index].pfn << PAGE_SHIFT);
+
+ bd->disk = alloc_disk(1);
+ if (!bd->disk) {
+ err = -ENOMEM;
+ goto out_free_bd;
+ }
+
+ bd->disk->queue = blk_init_queue(do_lgb_request, &bd->lock);
+ if (!bd->disk->queue) {
+ err = -ENOMEM;
+ goto out_put;
+ }
+
+ /* We can only handle a certain number of sg entries */
+ blk_queue_max_hw_segments(bd->disk->queue, LGUEST_MAX_DMA_SECTIONS);
+ /* Buffers must not cross page boundaries */
+ blk_queue_segment_boundary(bd->disk->queue, PAGE_SIZE-1);
+
+ bd->irq = lhdev->index+1;
+ bd->major = register_blkdev(0, "lguestblk");
+ if (bd->major < 0) {
+ err = bd->major;
+ goto out_cleanup_queue;
+ }
+ bd->lb_page = (void *)ioremap(bd->phys_addr, PAGE_SIZE);
+ bd->req = NULL;
+
+ sprintf(bd->disk->disk_name, "lgb%c", next_block_index++);
+ if (lguest_devices[lhdev->index].features & LGUEST_DEVICE_F_RANDOMNESS)
+ irqflags |= IRQF_SAMPLE_RANDOM;
+ err = request_irq(bd->irq, lgb_irq, irqflags, bd->disk->disk_name, bd);
+ if (err)
+ goto out_unmap;
+
+ bd->dma.used_len = 0;
+ bd->dma.len[0] = 0;
+ hcall(LHCALL_BIND_DMA, bd->phys_addr, __pa(&bd->dma), (1<<8)+bd->irq);
+
+ printk(KERN_INFO "%s: device %i at major %d\n",
+ bd->disk->disk_name, lhdev->index, bd->major);
+
+ bd->disk->major = bd->major;
+ bd->disk->first_minor = 0;
+ bd->disk->private_data = bd;
+ bd->disk->fops = &lguestblk_fops;
+ /* This is initialized to the disk size by the other end. */
+ set_capacity(bd->disk, bd->lb_page->num_sectors);
+ add_disk(bd->disk);
+
+ lhdev->private = bd;
+ return 0;
+
+out_unmap:
+ iounmap(bd->lb_page);
+out_cleanup_queue:
+ blk_cleanup_queue(bd->disk->queue);
+out_put:
+ put_disk(bd->disk);
+out_free_bd:
+ kfree(bd);
+ return err;
+}
+
+static struct lguest_driver lguestblk_drv = {
+ .name = "lguestblk",
+ .owner = THIS_MODULE,
+ .device_type = LGUEST_DEVICE_T_BLOCK,
+ .probe = lguestblk_probe,
+};
+
+static __init int lguestblk_init(void)
+{
+ return register_lguest_driver(&lguestblk_drv);
+}
+module_init(lguestblk_init);
+
+MODULE_DESCRIPTION("Lguest block driver");
+MODULE_LICENSE("GPL");

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