diff options
Diffstat (limited to 'drivers/xen/blkback/blkback.c')
| -rw-r--r-- | drivers/xen/blkback/blkback.c | 656 |
1 files changed, 656 insertions, 0 deletions
diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c new file mode 100644 index 000000000000..5b8d50e344b4 --- /dev/null +++ b/drivers/xen/blkback/blkback.c @@ -0,0 +1,656 @@ +/****************************************************************************** + * arch/xen/drivers/blkif/backend/main.c + * + * Back-end of the driver for virtual block devices. This portion of the + * driver exports a 'unified' block-device interface that can be accessed + * by any operating system that implements a compatible front end. A + * reference front-end implementation can be found in: + * arch/xen/drivers/blkif/frontend + * + * Copyright (c) 2003-2004, Keir Fraser & Steve Hand + * Copyright (c) 2005, Christopher Clark + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License version 2 + * as published by the Free Software Foundation; or, when distributed + * separately from the Linux kernel or incorporated into other + * software packages, subject to the following license: + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this source file (the "Software"), to deal in the Software without + * restriction, including without limitation the rights to use, copy, modify, + * merge, publish, distribute, sublicense, and/or sell copies of the Software, + * and to permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + */ + +#include <linux/spinlock.h> +#include <linux/kthread.h> +#include <linux/list.h> +#include <linux/delay.h> +#include <xen/balloon.h> +#include <asm/hypervisor.h> +#include "common.h" + +/* + * These are rather arbitrary. They are fairly large because adjacent requests + * pulled from a communication ring are quite likely to end up being part of + * the same scatter/gather request at the disc. + * + * ** TRY INCREASING 'blkif_reqs' IF WRITE SPEEDS SEEM TOO LOW ** + * + * This will increase the chances of being able to write whole tracks. + * 64 should be enough to keep us competitive with Linux. + */ +static int blkif_reqs = 64; +module_param_named(reqs, blkif_reqs, int, 0); +MODULE_PARM_DESC(reqs, "Number of blkback requests to allocate"); + +/* Run-time switchable: /sys/module/blkback/parameters/ */ +static unsigned int log_stats = 0; +static unsigned int debug_lvl = 0; +module_param(log_stats, int, 0644); +module_param(debug_lvl, int, 0644); + +/* + * Each outstanding request that we've passed to the lower device layers has a + * 'pending_req' allocated to it. Each buffer_head that completes decrements + * the pendcnt towards zero. When it hits zero, the specified domain has a + * response queued for it, with the saved 'id' passed back. + */ +typedef struct { + blkif_t *blkif; + u64 id; + int nr_pages; + atomic_t pendcnt; + unsigned short operation; + int status; + struct list_head free_list; +} pending_req_t; + +static pending_req_t *pending_reqs; +static struct list_head pending_free; +static DEFINE_SPINLOCK(pending_free_lock); +static DECLARE_WAIT_QUEUE_HEAD(pending_free_wq); + +#define BLKBACK_INVALID_HANDLE (~0) + +static struct page **pending_pages; +static grant_handle_t *pending_grant_handles; + +static inline int vaddr_pagenr(pending_req_t *req, int seg) +{ + return (req - pending_reqs) * BLKIF_MAX_SEGMENTS_PER_REQUEST + seg; +} + +static inline unsigned long vaddr(pending_req_t *req, int seg) +{ + unsigned long pfn = page_to_pfn(pending_pages[vaddr_pagenr(req, seg)]); + return (unsigned long)pfn_to_kaddr(pfn); +} + +#define pending_handle(_req, _seg) \ + (pending_grant_handles[vaddr_pagenr(_req, _seg)]) + + +static int do_block_io_op(blkif_t *blkif); +static void dispatch_rw_block_io(blkif_t *blkif, + blkif_request_t *req, + pending_req_t *pending_req); +static void make_response(blkif_t *blkif, u64 id, + unsigned short op, int st); + +/****************************************************************** + * misc small helpers + */ +static pending_req_t* alloc_req(void) +{ + pending_req_t *req = NULL; + unsigned long flags; + + spin_lock_irqsave(&pending_free_lock, flags); + if (!list_empty(&pending_free)) { + req = list_entry(pending_free.next, pending_req_t, free_list); + list_del(&req->free_list); + } + spin_unlock_irqrestore(&pending_free_lock, flags); + return req; +} + +static void free_req(pending_req_t *req) +{ + unsigned long flags; + int was_empty; + + spin_lock_irqsave(&pending_free_lock, flags); + was_empty = list_empty(&pending_free); + list_add(&req->free_list, &pending_free); + spin_unlock_irqrestore(&pending_free_lock, flags); + if (was_empty) + wake_up(&pending_free_wq); +} + +static void unplug_queue(blkif_t *blkif) +{ + if (blkif->plug == NULL) + return; + if (blkif->plug->unplug_fn) + blkif->plug->unplug_fn(blkif->plug); + blk_put_queue(blkif->plug); + blkif->plug = NULL; +} + +static void plug_queue(blkif_t *blkif, struct block_device *bdev) +{ + request_queue_t *q = bdev_get_queue(bdev); + + if (q == blkif->plug) + return; + unplug_queue(blkif); + blk_get_queue(q); + blkif->plug = q; +} + +static void fast_flush_area(pending_req_t *req) +{ + struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + unsigned int i, invcount = 0; + grant_handle_t handle; + int ret; + + for (i = 0; i < req->nr_pages; i++) { + handle = pending_handle(req, i); + if (handle == BLKBACK_INVALID_HANDLE) + continue; + gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i), + GNTMAP_host_map, handle); + pending_handle(req, i) = BLKBACK_INVALID_HANDLE; + invcount++; + } + + ret = HYPERVISOR_grant_table_op( + GNTTABOP_unmap_grant_ref, unmap, invcount); + BUG_ON(ret); +} + +/****************************************************************** + * SCHEDULER FUNCTIONS + */ + +static void print_stats(blkif_t *blkif) +{ + printk(KERN_DEBUG "%s: oo %3d | rd %4d | wr %4d | br %4d\n", + current->comm, blkif->st_oo_req, + blkif->st_rd_req, blkif->st_wr_req, blkif->st_br_req); + blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000); + blkif->st_rd_req = 0; + blkif->st_wr_req = 0; + blkif->st_oo_req = 0; +} + +int blkif_schedule(void *arg) +{ + blkif_t *blkif = arg; + + blkif_get(blkif); + + if (debug_lvl) + printk(KERN_DEBUG "%s: started\n", current->comm); + + while (!kthread_should_stop()) { + if (try_to_freeze()) + continue; + + wait_event_interruptible( + blkif->wq, + blkif->waiting_reqs || kthread_should_stop()); + wait_event_interruptible( + pending_free_wq, + !list_empty(&pending_free) || kthread_should_stop()); + + blkif->waiting_reqs = 0; + smp_mb(); /* clear flag *before* checking for work */ + + if (do_block_io_op(blkif)) + blkif->waiting_reqs = 1; + unplug_queue(blkif); + + if (log_stats && time_after(jiffies, blkif->st_print)) + print_stats(blkif); + } + + if (log_stats) + print_stats(blkif); + if (debug_lvl) + printk(KERN_DEBUG "%s: exiting\n", current->comm); + + blkif->xenblkd = NULL; + blkif_put(blkif); + + return 0; +} + +/****************************************************************** + * COMPLETION CALLBACK -- Called as bh->b_end_io() + */ + +static void __end_block_io_op(pending_req_t *pending_req, int error) +{ + /* An error fails the entire request. */ + if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) && + (error == -EOPNOTSUPP)) { + DPRINTK("blkback: write barrier op failed, not supported\n"); + blkback_barrier(XBT_NIL, pending_req->blkif->be, 0); + pending_req->status = BLKIF_RSP_EOPNOTSUPP; + } else if (error) { + DPRINTK("Buffer not up-to-date at end of operation, " + "error=%d\n", error); + pending_req->status = BLKIF_RSP_ERROR; + } + + if (atomic_dec_and_test(&pending_req->pendcnt)) { + fast_flush_area(pending_req); + make_response(pending_req->blkif, pending_req->id, + pending_req->operation, pending_req->status); + blkif_put(pending_req->blkif); + free_req(pending_req); + } +} + +static int end_block_io_op(struct bio *bio, unsigned int done, int error) +{ + if (bio->bi_size != 0) + return 1; + __end_block_io_op(bio->bi_private, error); + bio_put(bio); + return error; +} + + +/****************************************************************************** + * NOTIFICATION FROM GUEST OS. + */ + +static void blkif_notify_work(blkif_t *blkif) +{ + blkif->waiting_reqs = 1; + wake_up(&blkif->wq); +} + +irqreturn_t blkif_be_int(int irq, void *dev_id, struct pt_regs *regs) +{ + blkif_notify_work(dev_id); + return IRQ_HANDLED; +} + + + +/****************************************************************** + * DOWNWARD CALLS -- These interface with the block-device layer proper. + */ + +static int do_block_io_op(blkif_t *blkif) +{ + blkif_back_rings_t *blk_rings = &blkif->blk_rings; + blkif_request_t req; + pending_req_t *pending_req; + RING_IDX rc, rp; + int more_to_do = 0; + + rc = blk_rings->common.req_cons; + rp = blk_rings->common.sring->req_prod; + rmb(); /* Ensure we see queued requests up to 'rp'. */ + + while (rc != rp) { + + if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc)) + break; + + pending_req = alloc_req(); + if (NULL == pending_req) { + blkif->st_oo_req++; + more_to_do = 1; + break; + } + + if (kthread_should_stop()) { + more_to_do = 1; + break; + } + + switch (blkif->blk_protocol) { + case BLKIF_PROTOCOL_NATIVE: + memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req)); + break; + case BLKIF_PROTOCOL_X86_32: + blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc)); + break; + case BLKIF_PROTOCOL_X86_64: + blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc)); + break; + default: + BUG(); + } + blk_rings->common.req_cons = ++rc; /* before make_response() */ + + /* Apply all sanity checks to /private copy/ of request. */ + barrier(); + + switch (req.operation) { + case BLKIF_OP_READ: + blkif->st_rd_req++; + dispatch_rw_block_io(blkif, &req, pending_req); + break; + case BLKIF_OP_WRITE_BARRIER: + blkif->st_br_req++; + /* fall through */ + case BLKIF_OP_WRITE: + blkif->st_wr_req++; + dispatch_rw_block_io(blkif, &req, pending_req); + break; + default: + /* A good sign something is wrong: sleep for a while to + * avoid excessive CPU consumption by a bad guest. */ + msleep(1); + DPRINTK("error: unknown block io operation [%d]\n", + req.operation); + make_response(blkif, req.id, req.operation, + BLKIF_RSP_ERROR); + free_req(pending_req); + break; + } + + /* Yield point for this unbounded loop. */ + cond_resched(); + } + + return more_to_do; +} + +static void dispatch_rw_block_io(blkif_t *blkif, + blkif_request_t *req, + pending_req_t *pending_req) +{ + extern void ll_rw_block(int rw, int nr, struct buffer_head * bhs[]); + struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct phys_req preq; + struct { + unsigned long buf; unsigned int nsec; + } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + unsigned int nseg; + struct bio *bio = NULL; + int ret, i; + int operation; + + switch (req->operation) { + case BLKIF_OP_READ: + operation = READ; + break; + case BLKIF_OP_WRITE: + operation = WRITE; + break; + case BLKIF_OP_WRITE_BARRIER: + operation = WRITE_BARRIER; + break; + default: + operation = 0; /* make gcc happy */ + BUG(); + } + + /* Check that number of segments is sane. */ + nseg = req->nr_segments; + if (unlikely(nseg == 0 && operation != WRITE_BARRIER) || + unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) { + DPRINTK("Bad number of segments in request (%d)\n", nseg); + goto fail_response; + } + + preq.dev = req->handle; + preq.sector_number = req->sector_number; + preq.nr_sects = 0; + + pending_req->blkif = blkif; + pending_req->id = req->id; + pending_req->operation = req->operation; + pending_req->status = BLKIF_RSP_OKAY; + pending_req->nr_pages = nseg; + + for (i = 0; i < nseg; i++) { + uint32_t flags; + + seg[i].nsec = req->seg[i].last_sect - + req->seg[i].first_sect + 1; + + if ((req->seg[i].last_sect >= (PAGE_SIZE >> 9)) || + (req->seg[i].last_sect < req->seg[i].first_sect)) + goto fail_response; + preq.nr_sects += seg[i].nsec; + + flags = GNTMAP_host_map; + if (operation != READ) + flags |= GNTMAP_readonly; + gnttab_set_map_op(&map[i], vaddr(pending_req, i), flags, + req->seg[i].gref, blkif->domid); + } + + ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map, nseg); + BUG_ON(ret); + + for (i = 0; i < nseg; i++) { + if (unlikely(map[i].status != 0)) { + DPRINTK("invalid buffer -- could not remap it\n"); + map[i].handle = BLKBACK_INVALID_HANDLE; + ret |= 1; + } + + pending_handle(pending_req, i) = map[i].handle; + + if (ret) + continue; + + set_phys_to_machine(__pa(vaddr( + pending_req, i)) >> PAGE_SHIFT, + FOREIGN_FRAME(map[i].dev_bus_addr >> PAGE_SHIFT)); + seg[i].buf = map[i].dev_bus_addr | + (req->seg[i].first_sect << 9); + } + + if (ret) + goto fail_flush; + + if (vbd_translate(&preq, blkif, operation) != 0) { + DPRINTK("access denied: %s of [%llu,%llu] on dev=%04x\n", + operation == READ ? "read" : "write", + preq.sector_number, + preq.sector_number + preq.nr_sects, preq.dev); + goto fail_flush; + } + + plug_queue(blkif, preq.bdev); + atomic_set(&pending_req->pendcnt, 1); + blkif_get(blkif); + + for (i = 0; i < nseg; i++) { + if (((int)preq.sector_number|(int)seg[i].nsec) & + ((bdev_hardsect_size(preq.bdev) >> 9) - 1)) { + DPRINTK("Misaligned I/O request from domain %d", + blkif->domid); + goto fail_put_bio; + } + + while ((bio == NULL) || + (bio_add_page(bio, + virt_to_page(vaddr(pending_req, i)), + seg[i].nsec << 9, + seg[i].buf & ~PAGE_MASK) == 0)) { + if (bio) { + atomic_inc(&pending_req->pendcnt); + submit_bio(operation, bio); + } + + bio = bio_alloc(GFP_KERNEL, nseg-i); + if (unlikely(bio == NULL)) + goto fail_put_bio; + + bio->bi_bdev = preq.bdev; + bio->bi_private = pending_req; + bio->bi_end_io = end_block_io_op; + bio->bi_sector = preq.sector_number; + } + + preq.sector_number += seg[i].nsec; + } + + if (!bio) { + BUG_ON(operation != WRITE_BARRIER); + bio = bio_alloc(GFP_KERNEL, 0); + if (unlikely(bio == NULL)) + goto fail_put_bio; + + bio->bi_bdev = preq.bdev; + bio->bi_private = pending_req; + bio->bi_end_io = end_block_io_op; + bio->bi_sector = -1; + } + + submit_bio(operation, bio); + + if (operation == READ) + blkif->st_rd_sect += preq.nr_sects; + else if (operation == WRITE || operation == WRITE_BARRIER) + blkif->st_wr_sect += preq.nr_sects; + + return; + + fail_flush: + fast_flush_area(pending_req); + fail_response: + make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR); + free_req(pending_req); + msleep(1); /* back off a bit */ + return; + + fail_put_bio: + __end_block_io_op(pending_req, -EINVAL); + if (bio) + bio_put(bio); + unplug_queue(blkif); + msleep(1); /* back off a bit */ + return; +} + + + +/****************************************************************** + * MISCELLANEOUS SETUP / TEARDOWN / DEBUGGING + */ + + +static void make_response(blkif_t *blkif, u64 id, + unsigned short op, int st) +{ + blkif_response_t resp; + unsigned long flags; + blkif_back_rings_t *blk_rings = &blkif->blk_rings; + int more_to_do = 0; + int notify; + + resp.id = id; + resp.operation = op; + resp.status = st; + + spin_lock_irqsave(&blkif->blk_ring_lock, flags); + /* Place on the response ring for the relevant domain. */ + switch (blkif->blk_protocol) { + case BLKIF_PROTOCOL_NATIVE: + memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt), + &resp, sizeof(resp)); + break; + case BLKIF_PROTOCOL_X86_32: + memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt), + &resp, sizeof(resp)); + break; + case BLKIF_PROTOCOL_X86_64: + memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt), + &resp, sizeof(resp)); + break; + default: + BUG(); + } + blk_rings->common.rsp_prod_pvt++; + RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify); + if (blk_rings->common.rsp_prod_pvt == blk_rings->common.req_cons) { + /* + * Tail check for pending requests. Allows frontend to avoid + * notifications if requests are already in flight (lower + * overheads and promotes batching). + */ + RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do); + + } else if (RING_HAS_UNCONSUMED_REQUESTS(&blk_rings->common)) { + more_to_do = 1; + } + + spin_unlock_irqrestore(&blkif->blk_ring_lock, flags); + + if (more_to_do) + blkif_notify_work(blkif); + if (notify) + notify_remote_via_irq(blkif->irq); +} + +static int __init blkif_init(void) +{ + int i, mmap_pages; + + if (!is_running_on_xen()) + return -ENODEV; + + mmap_pages = blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST; + + pending_reqs = kmalloc(sizeof(pending_reqs[0]) * + blkif_reqs, GFP_KERNEL); + pending_grant_handles = kmalloc(sizeof(pending_grant_handles[0]) * + mmap_pages, GFP_KERNEL); + pending_pages = alloc_empty_pages_and_pagevec(mmap_pages); + + if (!pending_reqs || !pending_grant_handles || !pending_pages) + goto out_of_memory; + + for (i = 0; i < mmap_pages; i++) + pending_grant_handles[i] = BLKBACK_INVALID_HANDLE; + + blkif_interface_init(); + + memset(pending_reqs, 0, sizeof(pending_reqs)); + INIT_LIST_HEAD(&pending_free); + + for (i = 0; i < blkif_reqs; i++) + list_add_tail(&pending_reqs[i].free_list, &pending_free); + + blkif_xenbus_init(); + + return 0; + + out_of_memory: + kfree(pending_reqs); + kfree(pending_grant_handles); + free_empty_pages_and_pagevec(pending_pages, mmap_pages); + printk("%s: out of memory\n", __FUNCTION__); + return -ENOMEM; +} + +module_init(blkif_init); + +MODULE_LICENSE("Dual BSD/GPL"); |