/****************************************************************************** * * 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: * drivers/block/xen-blkfront.c * * 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 #include #include #include #include #include #include #include #include #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 'xen_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 xen_blkif_reqs = 64; module_param_named(reqs, xen_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; static unsigned int debug_lvl; 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. */ struct pending_req { struct blkif_st *blkif; u64 id; int nr_pages; atomic_t pendcnt; unsigned short operation; int status; struct list_head free_list; }; #define BLKBACK_INVALID_HANDLE (~0) struct xen_blkbk { struct pending_req *pending_reqs; /* List of all 'pending_req' available */ struct list_head pending_free; /* And its spinlock. */ spinlock_t pending_free_lock; wait_queue_head_t pending_free_wq; /* The list of all pages that are available. */ struct page **pending_pages; /* And the grant handles that are available. */ grant_handle_t *pending_grant_handles; }; static struct xen_blkbk *blkbk; /* * Little helpful macro to figure out the index and virtual address of the * pending_pages[..]. For each 'pending_req' we have have up to * BLKIF_MAX_SEGMENTS_PER_REQUEST (11) pages. The seg would be from 0 through * 10 and would index in the pending_pages[..]. */ static inline int vaddr_pagenr(struct pending_req *req, int seg) { return (req - blkbk->pending_reqs) * BLKIF_MAX_SEGMENTS_PER_REQUEST + seg; } #define pending_page(req, seg) pending_pages[vaddr_pagenr(req, seg)] static inline unsigned long vaddr(struct pending_req *req, int seg) { unsigned long pfn = page_to_pfn(blkbk->pending_page(req, seg)); return (unsigned long)pfn_to_kaddr(pfn); } #define pending_handle(_req, _seg) \ (blkbk->pending_grant_handles[vaddr_pagenr(_req, _seg)]) static int do_block_io_op(struct blkif_st *blkif); static int dispatch_rw_block_io(struct blkif_st *blkif, struct blkif_request *req, struct pending_req *pending_req); static void make_response(struct blkif_st *blkif, u64 id, unsigned short op, int st); /* * Retrieve from the 'pending_reqs' a free pending_req structure to be used. */ static struct pending_req *alloc_req(void) { struct pending_req *req = NULL; unsigned long flags; spin_lock_irqsave(&blkbk->pending_free_lock, flags); if (!list_empty(&blkbk->pending_free)) { req = list_entry(blkbk->pending_free.next, struct pending_req, free_list); list_del(&req->free_list); } spin_unlock_irqrestore(&blkbk->pending_free_lock, flags); return req; } /* * Return the 'pending_req' structure back to the freepool. We also * wake up the thread if it was waiting for a free page. */ static void free_req(struct pending_req *req) { unsigned long flags; int was_empty; spin_lock_irqsave(&blkbk->pending_free_lock, flags); was_empty = list_empty(&blkbk->pending_free); list_add(&req->free_list, &blkbk->pending_free); spin_unlock_irqrestore(&blkbk->pending_free_lock, flags); if (was_empty) wake_up(&blkbk->pending_free_wq); } /* * Routines for managing virtual block devices (vbds). */ static int vbd_translate(struct phys_req *req, struct blkif_st *blkif, int operation) { struct vbd *vbd = &blkif->vbd; int rc = -EACCES; if ((operation != READ) && vbd->readonly) goto out; if (unlikely((req->sector_number + req->nr_sects) > vbd_sz(vbd))) goto out; req->dev = vbd->pdevice; req->bdev = vbd->bdev; rc = 0; out: return rc; } static void vbd_resize(struct blkif_st *blkif) { struct vbd *vbd = &blkif->vbd; struct xenbus_transaction xbt; int err; struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be); unsigned long long new_size = vbd_sz(vbd); pr_info("xen-blkback: VBD Resize: Domid: %d, Device: (%d, %d)\n", blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice)); pr_info("xen-blkback: VBD Resize: new size %llu\n", new_size); vbd->size = new_size; again: err = xenbus_transaction_start(&xbt); if (err) { pr_warn("xen-blkback: Error starting transaction"); return; } err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu", (unsigned long long)vbd_sz(vbd)); if (err) { pr_warn("xen-blkback: Error writing new size"); goto abort; } /* * Write the current state; we will use this to synchronize * the front-end. If the current state is "connected" the * front-end will get the new size information online. */ err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state); if (err) { pr_warn("xen-blkback: Error writing the state"); goto abort; } err = xenbus_transaction_end(xbt, 0); if (err == -EAGAIN) goto again; if (err) pr_warn("xen-blkback: Error ending transaction"); abort: xenbus_transaction_end(xbt, 1); } /* * Notification from the guest OS. */ static void blkif_notify_work(struct blkif_st *blkif) { blkif->waiting_reqs = 1; wake_up(&blkif->wq); } irqreturn_t xen_blkif_be_int(int irq, void *dev_id) { blkif_notify_work(dev_id); return IRQ_HANDLED; } /* * SCHEDULER FUNCTIONS */ static void print_stats(struct blkif_st *blkif) { pr_debug("xen-blkback (%s): oo %3d | rd %4d | wr %4d | f %4d\n", current->comm, blkif->st_oo_req, blkif->st_rd_req, blkif->st_wr_req, blkif->st_f_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 xen_blkif_schedule(void *arg) { struct blkif_st *blkif = arg; struct vbd *vbd = &blkif->vbd; xen_blkif_get(blkif); if (debug_lvl) pr_debug("xen-blkback: %s: started\n", current->comm); while (!kthread_should_stop()) { if (try_to_freeze()) continue; if (unlikely(vbd->size != vbd_sz(vbd))) vbd_resize(blkif); wait_event_interruptible( blkif->wq, blkif->waiting_reqs || kthread_should_stop()); wait_event_interruptible( blkbk->pending_free_wq, !list_empty(&blkbk->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; if (log_stats && time_after(jiffies, blkif->st_print)) print_stats(blkif); } if (log_stats) print_stats(blkif); if (debug_lvl) pr_debug("xen-blkback: %s: exiting\n", current->comm); blkif->xenblkd = NULL; xen_blkif_put(blkif); return 0; } struct seg_buf { unsigned long buf; unsigned int nsec; }; /* * Unmap the grant references, and also remove the M2P over-rides * used in the 'pending_req'. */ static void xen_blkbk_unmap(struct pending_req *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); /* * Note, we use invcount, so nr->pages, so we can't index * using vaddr(req, i). */ for (i = 0; i < invcount; i++) { ret = m2p_remove_override( virt_to_page(unmap[i].host_addr), false); if (ret) { pr_alert("xen-blkback: Failed to remove M2P override for %lx\n", (unsigned long)unmap[i].host_addr); continue; } } } static int xen_blkbk_map(struct blkif_request *req, struct pending_req *pending_req, struct seg_buf seg[]) { struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST]; int i; int nseg = req->nr_segments; int ret = 0; /* * Fill out preq.nr_sects with proper amount of sectors, and setup * assign map[..] with the PFN of the page in our domain with the * corresponding grant reference for each page. */ for (i = 0; i < nseg; i++) { uint32_t flags; flags = GNTMAP_host_map; if (pending_req->operation != BLKIF_OP_READ) flags |= GNTMAP_readonly; gnttab_set_map_op(&map[i], vaddr(pending_req, i), flags, req->u.rw.seg[i].gref, pending_req->blkif->domid); } ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map, nseg); BUG_ON(ret); /* * Now swizzle the MFN in our domain with the MFN from the other domain * so that when we access vaddr(pending_req,i) it has the contents of * the page from the other domain. */ for (i = 0; i < nseg; i++) { if (unlikely(map[i].status != 0)) { pr_debug("xen-blkback: 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; ret = m2p_add_override(PFN_DOWN(map[i].dev_bus_addr), blkbk->pending_page(pending_req, i), false); if (ret) { pr_alert("xen-blkback: Failed to install M2P override for %lx (ret: %d)\n", (unsigned long)map[i].dev_bus_addr, ret); /* We could switch over to GNTTABOP_copy */ continue; } seg[i].buf = map[i].dev_bus_addr | (req->u.rw.seg[i].first_sect << 9); } return ret; } /* * Completion callback on the bio's. Called as bh->b_end_io() */ static void __end_block_io_op(struct pending_req *pending_req, int error) { /* An error fails the entire request. */ if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) && (error == -EOPNOTSUPP)) { pr_debug("xen-blkback: flush diskcache op failed, not supported\n"); xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0); pending_req->status = BLKIF_RSP_EOPNOTSUPP; } else if (error) { pr_debug("xen-blkback: Buffer not up-to-date at end of operation," " error=%d\n", error); pending_req->status = BLKIF_RSP_ERROR; } /* * If all of the bio's have completed it is time to unmap * the grant references associated with 'request' and provide * the proper response on the ring. */ if (atomic_dec_and_test(&pending_req->pendcnt)) { xen_blkbk_unmap(pending_req); make_response(pending_req->blkif, pending_req->id, pending_req->operation, pending_req->status); xen_blkif_put(pending_req->blkif); free_req(pending_req); } } /* * bio callback. */ static void end_block_io_op(struct bio *bio, int error) { __end_block_io_op(bio->bi_private, error); bio_put(bio); } /* * Function to copy the from the ring buffer the 'struct blkif_request' * (which has the sectors we want, number of them, grant references, etc), * and transmute it to the block API to hand it over to the proper block disk. */ static int do_block_io_op(struct blkif_st *blkif) { union blkif_back_rings *blk_rings = &blkif->blk_rings; struct blkif_request req; struct pending_req *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; if (kthread_should_stop()) { more_to_do = 1; break; } pending_req = alloc_req(); if (NULL == pending_req) { blkif->st_oo_req++; 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(); if (dispatch_rw_block_io(blkif, &req, pending_req)) break; /* Yield point for this unbounded loop. */ cond_resched(); } return more_to_do; } /* * Transmutation of the 'struct blkif_request' to a proper 'struct bio' * and call the 'submit_bio' to pass it to the underlying storage. */ static int dispatch_rw_block_io(struct blkif_st *blkif, struct blkif_request *req, struct pending_req *pending_req) { struct phys_req preq; struct seg_buf seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; unsigned int nseg; struct bio *bio = NULL; struct bio *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST]; int i, nbio = 0; int operation; struct blk_plug plug; switch (req->operation) { case BLKIF_OP_READ: blkif->st_rd_req++; operation = READ; break; case BLKIF_OP_WRITE: blkif->st_wr_req++; operation = WRITE_ODIRECT; break; case BLKIF_OP_FLUSH_DISKCACHE: blkif->st_f_req++; operation = WRITE_FLUSH; /* * The frontend likes to set this to -1, which vbd_translate * is alergic too. */ req->u.rw.sector_number = 0; break; case BLKIF_OP_WRITE_BARRIER: default: operation = 0; /* make gcc happy */ goto fail_response; break; } /* Check that the number of segments is sane. */ nseg = req->nr_segments; if (unlikely(nseg == 0 && operation != WRITE_FLUSH) || unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) { pr_debug("xen-blkback: Bad number of segments in request (%d)\n", nseg); /* Haven't submitted any bio's yet. */ goto fail_response; } preq.dev = req->handle; preq.sector_number = req->u.rw.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++) { seg[i].nsec = req->u.rw.seg[i].last_sect - req->u.rw.seg[i].first_sect + 1; if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) || (req->u.rw.seg[i].last_sect < req->u.rw.seg[i].first_sect)) goto fail_response; preq.nr_sects += seg[i].nsec; } if (vbd_translate(&preq, blkif, operation) != 0) { pr_debug("xen-blkback: 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_response; } /* * This check _MUST_ be done after vbd_translate as the preq.bdev * is set there. */ for (i = 0; i < nseg; i++) { if (((int)preq.sector_number|(int)seg[i].nsec) & ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) { pr_debug("xen-blkback: Misaligned I/O request from domain %d", blkif->domid); goto fail_response; } } /* * If we have failed at this point, we need to undo the M2P override, * set gnttab_set_unmap_op on all of the grant references and perform * the hypercall to unmap the grants - that is all done in * xen_blkbk_unmap. */ if (xen_blkbk_map(req, pending_req, seg)) goto fail_flush; /* This corresponding xen_blkif_put is done in __end_block_io_op */ xen_blkif_get(blkif); for (i = 0; i < nseg; i++) { while ((bio == NULL) || (bio_add_page(bio, blkbk->pending_page(pending_req, i), seg[i].nsec << 9, seg[i].buf & ~PAGE_MASK) == 0)) { bio = biolist[nbio++] = 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; } /* This will be hit if the operation was a flush. */ if (!bio) { BUG_ON(operation != WRITE_FLUSH); bio = biolist[nbio++] = 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; } /* * We set it one so that the last submit_bio does not have to call * atomic_inc. */ atomic_set(&pending_req->pendcnt, nbio); /* Get a reference count for the disk queue and start sending I/O */ blk_start_plug(&plug); for (i = 0; i < nbio; i++) submit_bio(operation, biolist[i]); /* Let the I/Os go.. */ blk_finish_plug(&plug); if (operation == READ) blkif->st_rd_sect += preq.nr_sects; else if (operation == WRITE || operation == WRITE_FLUSH) blkif->st_wr_sect += preq.nr_sects; return 0; fail_flush: xen_blkbk_unmap(pending_req); fail_response: /* Haven't submitted any bio's yet. */ make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR); free_req(pending_req); msleep(1); /* back off a bit */ return -EIO; fail_put_bio: for (i = 0; i < (nbio-1); i++) bio_put(biolist[i]); __end_block_io_op(pending_req, -EINVAL); msleep(1); /* back off a bit */ return -EIO; } /* * Put a response on the ring on how the operation fared. */ static void make_response(struct blkif_st *blkif, u64 id, unsigned short op, int st) { struct blkif_response resp; unsigned long flags; union blkif_back_rings *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 xen_blkif_init(void) { int i, mmap_pages; int rc = 0; if (!xen_pv_domain()) return -ENODEV; blkbk = kzalloc(sizeof(struct xen_blkbk), GFP_KERNEL); if (!blkbk) { pr_alert("xen-blkback: %s: out of memory!\n", __func__); return -ENOMEM; } mmap_pages = xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST; blkbk->pending_reqs = kmalloc(sizeof(blkbk->pending_reqs[0]) * xen_blkif_reqs, GFP_KERNEL); blkbk->pending_grant_handles = kzalloc(sizeof(blkbk->pending_grant_handles[0]) * mmap_pages, GFP_KERNEL); blkbk->pending_pages = kzalloc(sizeof(blkbk->pending_pages[0]) * mmap_pages, GFP_KERNEL); if (!blkbk->pending_reqs || !blkbk->pending_grant_handles || !blkbk->pending_pages) { rc = -ENOMEM; goto out_of_memory; } for (i = 0; i < mmap_pages; i++) { blkbk->pending_grant_handles[i] = BLKBACK_INVALID_HANDLE; blkbk->pending_pages[i] = alloc_page(GFP_KERNEL); if (blkbk->pending_pages[i] == NULL) { rc = -ENOMEM; goto out_of_memory; } } rc = xen_blkif_interface_init(); if (rc) goto failed_init; memset(blkbk->pending_reqs, 0, sizeof(blkbk->pending_reqs)); INIT_LIST_HEAD(&blkbk->pending_free); spin_lock_init(&blkbk->pending_free_lock); init_waitqueue_head(&blkbk->pending_free_wq); for (i = 0; i < xen_blkif_reqs; i++) list_add_tail(&blkbk->pending_reqs[i].free_list, &blkbk->pending_free); rc = xen_blkif_xenbus_init(); if (rc) goto failed_init; return 0; out_of_memory: pr_alert("xen-blkback: %s: out of memory\n", __func__); failed_init: kfree(blkbk->pending_reqs); kfree(blkbk->pending_grant_handles); for (i = 0; i < mmap_pages; i++) { if (blkbk->pending_pages[i]) __free_page(blkbk->pending_pages[i]); } kfree(blkbk->pending_pages); kfree(blkbk); blkbk = NULL; return rc; } module_init(xen_blkif_init); MODULE_LICENSE("Dual BSD/GPL");