diff options
Diffstat (limited to 'drivers/block/lguest_blk.c')
| -rw-r--r-- | drivers/block/lguest_blk.c | 421 |
1 files changed, 0 insertions, 421 deletions
diff --git a/drivers/block/lguest_blk.c b/drivers/block/lguest_blk.c deleted file mode 100644 index fa8e42341b8..00000000000 --- a/drivers/block/lguest_blk.c +++ /dev/null @@ -1,421 +0,0 @@ -/*D:400 - * The Guest block driver - * - * This is a simple block driver, which appears as /dev/lgba, lgbb, lgbc etc. - * The mechanism is simple: we place the information about the request in the - * device page, then use SEND_DMA (containing the data for a write, or an empty - * "ping" DMA for a read). - :*/ -/* 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 <linux/lguest_bus.h> - -static char next_block_index = 'a'; - -/*D:420 Here is the structure which holds all the information we need about - * each Guest block device. - * - * I'm sure at this stage, you're wondering "hey, where was the adventure I was - * promised?" and thinking "Rusty sucks, I shall say nasty things about him on - * my blog". I think Real adventures have boring bits, too, and you're in the - * middle of one. But it gets better. Just not quite yet. */ -struct blockdev -{ - /* The block queue infrastructure wants a spinlock: it is held while it - * calls our block request function. We grab it in our interrupt - * handler so the responses don't mess with new requests. */ - spinlock_t lock; - - /* The disk structure registered with kernel. */ - struct gendisk *disk; - - /* The major device number for this disk, and the interrupt. We only - * really keep them here for completeness; we'd need them if we - * supported device unplugging. */ - int major; - int irq; - - /* The physical address of this device's memory page */ - unsigned long phys_addr; - /* The mapped memory page for convenient acces. */ - struct lguest_block_page *lb_page; - - /* We only have a single request outstanding at a time: this is it. */ - struct lguest_dma dma; - struct request *req; -}; - -/*D:495 We originally used end_request() throughout the driver, but it turns - * out that end_request() is deprecated, and doesn't actually end the request - * (which seems like a good reason to deprecate it!). It simply ends the first - * bio. So if we had 3 bios in a "struct request" we would do all 3, - * end_request(), do 2, end_request(), do 1 and end_request(): twice as much - * work as we needed to do. - * - * This reinforced to me that I do not understand the block layer. - * - * Nonetheless, Jens Axboe gave me this nice helper to end all chunks of a - * request. This improved disk speed by 130%. */ -static void end_entire_request(struct request *req, int uptodate) -{ - if (end_that_request_first(req, uptodate, req->hard_nr_sectors)) - BUG(); - add_disk_randomness(req->rq_disk); - blkdev_dequeue_request(req); - end_that_request_last(req, uptodate); -} - -/* I'm told there are only two stories in the world worth telling: love and - * hate. So there used to be a love scene here like this: - * - * Launcher: We could make beautiful I/O together, you and I. - * Guest: My, that's a big disk! - * - * Unfortunately, it was just too raunchy for our otherwise-gentle tale. */ - -/*D:490 This is the interrupt handler, called when a block read or write has - * been completed for us. */ -static irqreturn_t lgb_irq(int irq, void *_bd) -{ - /* We handed our "struct blockdev" as the argument to request_irq(), so - * it is passed through to us here. This tells us which device we're - * dealing with in case we have more than one. */ - struct blockdev *bd = _bd; - unsigned long flags; - - /* We weren't doing anything? Strange, but could happen if we shared - * interrupts (we don't!). */ - if (!bd->req) { - pr_debug("No work!\n"); - return IRQ_NONE; - } - - /* Not done yet? That's equally strange. */ - if (!bd->lb_page->result) { - pr_debug("No result!\n"); - return IRQ_NONE; - } - - /* We have to grab the lock before ending the request. */ - spin_lock_irqsave(&bd->lock, flags); - /* "result" is 1 for success, 2 for failure: end_entire_request() wants - * to know whether this succeeded or not. */ - end_entire_request(bd->req, bd->lb_page->result == 1); - /* Clear out request, it's done. */ - bd->req = NULL; - /* Reset incoming DMA for next time. */ - bd->dma.used_len = 0; - /* Ready for more reads or writes */ - blk_start_queue(bd->disk->queue); - spin_unlock_irqrestore(&bd->lock, flags); - - /* The interrupt was for us, we dealt with it. */ - return IRQ_HANDLED; -} - -/*D:480 The block layer's "struct request" contains a number of "struct bio"s, - * each of which contains "struct bio_vec"s, each of which contains a page, an - * offset and a length. - * - * Fortunately there are iterators to help us walk through the "struct - * request". Even more fortunately, there were plenty of places to steal the - * code from. We pack the "struct request" into our "struct lguest_dma" and - * return the total length. */ -static unsigned int req_to_dma(struct request *req, struct lguest_dma *dma) -{ - unsigned int i = 0, len = 0; - struct req_iterator iter; - struct bio_vec *bvec; - - rq_for_each_segment(bvec, req, iter) { - /* We told the block layer not to give us too many. */ - BUG_ON(i == LGUEST_MAX_DMA_SECTIONS); - /* If we had a zero-length segment, it would look like - * the end of the data referred to by the "struct - * lguest_dma", so make sure that doesn't happen. */ - BUG_ON(!bvec->bv_len); - /* Convert page & offset to a physical address */ - dma->addr[i] = page_to_phys(bvec->bv_page) - + bvec->bv_offset; - dma->len[i] = bvec->bv_len; - len += bvec->bv_len; - i++; - } - /* If the array isn't full, we mark the end with a 0 length */ - if (i < LGUEST_MAX_DMA_SECTIONS) - dma->len[i] = 0; - return len; -} - -/* This creates an empty DMA, useful for prodding the Host without sending data - * (ie. when we want to do a read) */ -static void empty_dma(struct lguest_dma *dma) -{ - dma->len[0] = 0; -} - -/*D:470 Setting up a request is fairly easy: */ -static void setup_req(struct blockdev *bd, - int type, struct request *req, struct lguest_dma *dma) -{ - /* The type is 1 (write) or 0 (read). */ - bd->lb_page->type = type; - /* The sector on disk where the read or write starts. */ - bd->lb_page->sector = req->sector; - /* The result is initialized to 0 (unfinished). */ - bd->lb_page->result = 0; - /* The current request (so we can end it in the interrupt handler). */ - bd->req = req; - /* The number of bytes: returned as a side-effect of req_to_dma(), - * which packs the block layer's "struct request" into our "struct - * lguest_dma" */ - bd->lb_page->bytes = req_to_dma(req, dma); -} - -/*D:450 Write is pretty straightforward: we pack the request into a "struct - * lguest_dma", then use SEND_DMA to send the request. */ -static void 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); - - lguest_send_dma(bd->phys_addr, &send); -} - -/* Read is similar to write, except we pack the request into our receive - * "struct lguest_dma" and send through an empty DMA just to tell the Host that - * there's a request pending. */ -static void 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); - lguest_send_dma(bd->phys_addr, &ping); -} - -/*D:440 This where requests come in: we get handed the request queue and are - * expected to pull a "struct request" off it until we've finished them or - * we're waiting for a reply: */ -static void do_lgb_request(struct request_queue *q) -{ - struct blockdev *bd; - struct request *req; - -again: - /* This sometimes returns NULL even on the very first time around. I - * wonder if it's something to do with letting elves handle the request - * queue... */ - req = elv_next_request(q); - if (!req) - return; - - /* We attached the struct blockdev to the disk: get it back */ - bd = req->rq_disk->private_data; - /* Sometimes we get repeated requests after blk_stop_queue(), but we - * can only handle one at a time. */ - if (bd->req) - return; - - /* We only do reads and writes: no tricky business! */ - if (!blk_fs_request(req)) { - pr_debug("Got non-command 0x%08x\n", req->cmd_type); - req->errors++; - end_entire_request(req, 0); - goto again; - } - - if (rq_data_dir(req) == WRITE) - do_write(bd, req); - else - do_read(bd, req); - - /* We've put out the request, so stop any more coming in until we get - * an interrupt, which takes us to lgb_irq() to re-enable the queue. */ - blk_stop_queue(q); -} - -/*D:430 This is the "struct block_device_operations" we attach to the disk at - * the end of lguestblk_probe(). It doesn't seem to want much. */ -static struct block_device_operations lguestblk_fops = { - .owner = THIS_MODULE, -}; - -/*D:425 Setting up a disk device seems to involve a lot of code. I'm not sure - * quite why. I do know that the IDE code sent two or three of the maintainers - * insane, perhaps this is the fringe of the same disease? - * - * As in the console code, the probe function gets handed the generic - * lguest_device from lguest_bus.c: */ -static int lguestblk_probe(struct lguest_device *lgdev) -{ - struct blockdev *bd; - int err; - int irqflags = IRQF_SHARED; - - /* First we allocate our own "struct blockdev" and initialize the easy - * fields. */ - bd = kmalloc(sizeof(*bd), GFP_KERNEL); - if (!bd) - return -ENOMEM; - - spin_lock_init(&bd->lock); - bd->irq = lgdev_irq(lgdev); - bd->req = NULL; - bd->dma.used_len = 0; - bd->dma.len[0] = 0; - /* The descriptor in the lguest_devices array provided by the Host - * gives the Guest the physical page number of the device's page. */ - bd->phys_addr = (lguest_devices[lgdev->index].pfn << PAGE_SHIFT); - - /* We use lguest_map() to get a pointer to the device page */ - bd->lb_page = lguest_map(bd->phys_addr, 1); - if (!bd->lb_page) { - err = -ENOMEM; - goto out_free_bd; - } - - /* We need a major device number: 0 means "assign one dynamically". */ - bd->major = register_blkdev(0, "lguestblk"); - if (bd->major < 0) { - err = bd->major; - goto out_unmap; - } - - /* This allocates a "struct gendisk" where we pack all the information - * about the disk which the rest of Linux sees. The argument is the - * number of minor devices desired: we need one minor for the main - * disk, and one for each partition. Of course, we can't possibly know - * how many partitions are on the disk (add_disk does that). - */ - bd->disk = alloc_disk(16); - if (!bd->disk) { - err = -ENOMEM; - goto out_unregister_blkdev; - } - - /* Every disk needs a queue for requests to come in: we set up the - * queue with a callback function (the core of our driver) and the lock - * to use. */ - bd->disk->queue = blk_init_queue(do_lgb_request, &bd->lock); - if (!bd->disk->queue) { - err = -ENOMEM; - goto out_put_disk; - } - - /* We can only handle a certain number of pointers in our SEND_DMA - * call, so we set that with blk_queue_max_hw_segments(). This is not - * to be confused with blk_queue_max_phys_segments() of course! I - * know, who could possibly confuse the two? - * - * Well, it's simple to tell them apart: this one seems to work and the - * other one didn't. */ - blk_queue_max_hw_segments(bd->disk->queue, LGUEST_MAX_DMA_SECTIONS); - - /* Due to technical limitations of our Host (and simple coding) we - * can't have a single buffer which crosses a page boundary. Tell it - * here. This means that our maximum request size is 16 - * (LGUEST_MAX_DMA_SECTIONS) pages. */ - blk_queue_segment_boundary(bd->disk->queue, PAGE_SIZE-1); - - /* We name our disk: this becomes the device name when udev does its - * magic thing and creates the device node, such as /dev/lgba. - * next_block_index is a global which starts at 'a'. Unfortunately - * this simple increment logic means that the 27th disk will be called - * "/dev/lgb{". In that case, I recommend having at least 29 disks, so - * your /dev directory will be balanced. */ - sprintf(bd->disk->disk_name, "lgb%c", next_block_index++); - - /* We look to the device descriptor again to see if this device's - * interrupts are expected to be random. If they are, we tell the irq - * subsystem. At the moment this bit is always set. */ - if (lguest_devices[lgdev->index].features & LGUEST_DEVICE_F_RANDOMNESS) - irqflags |= IRQF_SAMPLE_RANDOM; - - /* Now we have the name and irqflags, we can request the interrupt; we - * give it the "struct blockdev" we have set up to pass to lgb_irq() - * when there is an interrupt. */ - err = request_irq(bd->irq, lgb_irq, irqflags, bd->disk->disk_name, bd); - if (err) - goto out_cleanup_queue; - - /* We bind our one-entry DMA pool to the key for this block device so - * the Host can reply to our requests. The key is equal to the - * physical address of the device's page, which is conveniently - * unique. */ - err = lguest_bind_dma(bd->phys_addr, &bd->dma, 1, bd->irq); - if (err) - goto out_free_irq; - - /* We finish our disk initialization and add the disk to the system. */ - 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 Launcher. */ - set_capacity(bd->disk, bd->lb_page->num_sectors); - add_disk(bd->disk); - - printk(KERN_INFO "%s: device %i at major %d\n", - bd->disk->disk_name, lgdev->index, bd->major); - - /* We don't need to keep the "struct blockdev" around, but if we ever - * implemented device removal, we'd need this. */ - lgdev->private = bd; - return 0; - -out_free_irq: - free_irq(bd->irq, bd); -out_cleanup_queue: - blk_cleanup_queue(bd->disk->queue); -out_put_disk: - put_disk(bd->disk); -out_unregister_blkdev: - unregister_blkdev(bd->major, "lguestblk"); -out_unmap: - lguest_unmap(bd->lb_page); -out_free_bd: - kfree(bd); - return err; -} - -/*D:410 The boilerplate code for registering the lguest block driver is just - * like the console: */ -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"); |