diff options
Diffstat (limited to 'drivers/block/xen-blkback/blkback.c')
| -rw-r--r-- | drivers/block/xen-blkback/blkback.c | 1456 |
1 files changed, 1456 insertions, 0 deletions
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c new file mode 100644 index 000000000..713fc9ff1 --- /dev/null +++ b/drivers/block/xen-blkback/blkback.c @@ -0,0 +1,1456 @@ +/****************************************************************************** + * + * 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. + */ + +#define pr_fmt(fmt) "xen-blkback: " fmt + +#include <linux/spinlock.h> +#include <linux/kthread.h> +#include <linux/list.h> +#include <linux/delay.h> +#include <linux/freezer.h> +#include <linux/bitmap.h> + +#include <xen/events.h> +#include <xen/page.h> +#include <xen/xen.h> +#include <asm/xen/hypervisor.h> +#include <asm/xen/hypercall.h> +#include <xen/balloon.h> +#include <xen/grant_table.h> +#include "common.h" + +/* + * Maximum number of unused free pages to keep in the internal buffer. + * Setting this to a value too low will reduce memory used in each backend, + * but can have a performance penalty. + * + * A sane value is xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST, but can + * be set to a lower value that might degrade performance on some intensive + * IO workloads. + */ + +static int xen_blkif_max_buffer_pages = 1024; +module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644); +MODULE_PARM_DESC(max_buffer_pages, +"Maximum number of free pages to keep in each block backend buffer"); + +/* + * Maximum number of grants to map persistently in blkback. For maximum + * performance this should be the total numbers of grants that can be used + * to fill the ring, but since this might become too high, specially with + * the use of indirect descriptors, we set it to a value that provides good + * performance without using too much memory. + * + * When the list of persistent grants is full we clean it up using a LRU + * algorithm. + */ + +static int xen_blkif_max_pgrants = 1056; +module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644); +MODULE_PARM_DESC(max_persistent_grants, + "Maximum number of grants to map persistently"); + +/* + * The LRU mechanism to clean the lists of persistent grants needs to + * be executed periodically. The time interval between consecutive executions + * of the purge mechanism is set in ms. + */ +#define LRU_INTERVAL 100 + +/* + * When the persistent grants list is full we will remove unused grants + * from the list. The percent number of grants to be removed at each LRU + * execution. + */ +#define LRU_PERCENT_CLEAN 5 + +/* Run-time switchable: /sys/module/blkback/parameters/ */ +static unsigned int log_stats; +module_param(log_stats, int, 0644); + +#define BLKBACK_INVALID_HANDLE (~0) + +/* Number of free pages to remove on each call to gnttab_free_pages */ +#define NUM_BATCH_FREE_PAGES 10 + +static inline int get_free_page(struct xen_blkif *blkif, struct page **page) +{ + unsigned long flags; + + spin_lock_irqsave(&blkif->free_pages_lock, flags); + if (list_empty(&blkif->free_pages)) { + BUG_ON(blkif->free_pages_num != 0); + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); + return gnttab_alloc_pages(1, page); + } + BUG_ON(blkif->free_pages_num == 0); + page[0] = list_first_entry(&blkif->free_pages, struct page, lru); + list_del(&page[0]->lru); + blkif->free_pages_num--; + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); + + return 0; +} + +static inline void put_free_pages(struct xen_blkif *blkif, struct page **page, + int num) +{ + unsigned long flags; + int i; + + spin_lock_irqsave(&blkif->free_pages_lock, flags); + for (i = 0; i < num; i++) + list_add(&page[i]->lru, &blkif->free_pages); + blkif->free_pages_num += num; + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); +} + +static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num) +{ + /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */ + struct page *page[NUM_BATCH_FREE_PAGES]; + unsigned int num_pages = 0; + unsigned long flags; + + spin_lock_irqsave(&blkif->free_pages_lock, flags); + while (blkif->free_pages_num > num) { + BUG_ON(list_empty(&blkif->free_pages)); + page[num_pages] = list_first_entry(&blkif->free_pages, + struct page, lru); + list_del(&page[num_pages]->lru); + blkif->free_pages_num--; + if (++num_pages == NUM_BATCH_FREE_PAGES) { + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); + gnttab_free_pages(num_pages, page); + spin_lock_irqsave(&blkif->free_pages_lock, flags); + num_pages = 0; + } + } + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); + if (num_pages != 0) + gnttab_free_pages(num_pages, page); +} + +#define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page))) + +static int do_block_io_op(struct xen_blkif *blkif); +static int dispatch_rw_block_io(struct xen_blkif *blkif, + struct blkif_request *req, + struct pending_req *pending_req); +static void make_response(struct xen_blkif *blkif, u64 id, + unsigned short op, int st); + +#define foreach_grant_safe(pos, n, rbtree, node) \ + for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \ + (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \ + &(pos)->node != NULL; \ + (pos) = container_of(n, typeof(*(pos)), node), \ + (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL) + + +/* + * We don't need locking around the persistent grant helpers + * because blkback uses a single-thread for each backed, so we + * can be sure that this functions will never be called recursively. + * + * The only exception to that is put_persistent_grant, that can be called + * from interrupt context (by xen_blkbk_unmap), so we have to use atomic + * bit operations to modify the flags of a persistent grant and to count + * the number of used grants. + */ +static int add_persistent_gnt(struct xen_blkif *blkif, + struct persistent_gnt *persistent_gnt) +{ + struct rb_node **new = NULL, *parent = NULL; + struct persistent_gnt *this; + + if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) { + if (!blkif->vbd.overflow_max_grants) + blkif->vbd.overflow_max_grants = 1; + return -EBUSY; + } + /* Figure out where to put new node */ + new = &blkif->persistent_gnts.rb_node; + while (*new) { + this = container_of(*new, struct persistent_gnt, node); + + parent = *new; + if (persistent_gnt->gnt < this->gnt) + new = &((*new)->rb_left); + else if (persistent_gnt->gnt > this->gnt) + new = &((*new)->rb_right); + else { + pr_alert_ratelimited("trying to add a gref that's already in the tree\n"); + return -EINVAL; + } + } + + bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE); + set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); + /* Add new node and rebalance tree. */ + rb_link_node(&(persistent_gnt->node), parent, new); + rb_insert_color(&(persistent_gnt->node), &blkif->persistent_gnts); + blkif->persistent_gnt_c++; + atomic_inc(&blkif->persistent_gnt_in_use); + return 0; +} + +static struct persistent_gnt *get_persistent_gnt(struct xen_blkif *blkif, + grant_ref_t gref) +{ + struct persistent_gnt *data; + struct rb_node *node = NULL; + + node = blkif->persistent_gnts.rb_node; + while (node) { + data = container_of(node, struct persistent_gnt, node); + + if (gref < data->gnt) + node = node->rb_left; + else if (gref > data->gnt) + node = node->rb_right; + else { + if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) { + pr_alert_ratelimited("requesting a grant already in use\n"); + return NULL; + } + set_bit(PERSISTENT_GNT_ACTIVE, data->flags); + atomic_inc(&blkif->persistent_gnt_in_use); + return data; + } + } + return NULL; +} + +static void put_persistent_gnt(struct xen_blkif *blkif, + struct persistent_gnt *persistent_gnt) +{ + if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) + pr_alert_ratelimited("freeing a grant already unused\n"); + set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); + clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); + atomic_dec(&blkif->persistent_gnt_in_use); +} + +static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root, + unsigned int num) +{ + struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct persistent_gnt *persistent_gnt; + struct rb_node *n; + int segs_to_unmap = 0; + struct gntab_unmap_queue_data unmap_data; + + unmap_data.pages = pages; + unmap_data.unmap_ops = unmap; + unmap_data.kunmap_ops = NULL; + + foreach_grant_safe(persistent_gnt, n, root, node) { + BUG_ON(persistent_gnt->handle == + BLKBACK_INVALID_HANDLE); + gnttab_set_unmap_op(&unmap[segs_to_unmap], + (unsigned long) pfn_to_kaddr(page_to_pfn( + persistent_gnt->page)), + GNTMAP_host_map, + persistent_gnt->handle); + + pages[segs_to_unmap] = persistent_gnt->page; + + if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST || + !rb_next(&persistent_gnt->node)) { + + unmap_data.count = segs_to_unmap; + BUG_ON(gnttab_unmap_refs_sync(&unmap_data)); + + put_free_pages(blkif, pages, segs_to_unmap); + segs_to_unmap = 0; + } + + rb_erase(&persistent_gnt->node, root); + kfree(persistent_gnt); + num--; + } + BUG_ON(num != 0); +} + +void xen_blkbk_unmap_purged_grants(struct work_struct *work) +{ + struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct persistent_gnt *persistent_gnt; + int segs_to_unmap = 0; + struct xen_blkif *blkif = container_of(work, typeof(*blkif), persistent_purge_work); + struct gntab_unmap_queue_data unmap_data; + + unmap_data.pages = pages; + unmap_data.unmap_ops = unmap; + unmap_data.kunmap_ops = NULL; + + while(!list_empty(&blkif->persistent_purge_list)) { + persistent_gnt = list_first_entry(&blkif->persistent_purge_list, + struct persistent_gnt, + remove_node); + list_del(&persistent_gnt->remove_node); + + gnttab_set_unmap_op(&unmap[segs_to_unmap], + vaddr(persistent_gnt->page), + GNTMAP_host_map, + persistent_gnt->handle); + + pages[segs_to_unmap] = persistent_gnt->page; + + if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) { + unmap_data.count = segs_to_unmap; + BUG_ON(gnttab_unmap_refs_sync(&unmap_data)); + put_free_pages(blkif, pages, segs_to_unmap); + segs_to_unmap = 0; + } + kfree(persistent_gnt); + } + if (segs_to_unmap > 0) { + unmap_data.count = segs_to_unmap; + BUG_ON(gnttab_unmap_refs_sync(&unmap_data)); + put_free_pages(blkif, pages, segs_to_unmap); + } +} + +static void purge_persistent_gnt(struct xen_blkif *blkif) +{ + struct persistent_gnt *persistent_gnt; + struct rb_node *n; + unsigned int num_clean, total; + bool scan_used = false, clean_used = false; + struct rb_root *root; + + if (blkif->persistent_gnt_c < xen_blkif_max_pgrants || + (blkif->persistent_gnt_c == xen_blkif_max_pgrants && + !blkif->vbd.overflow_max_grants)) { + return; + } + + if (work_pending(&blkif->persistent_purge_work)) { + pr_alert_ratelimited("Scheduled work from previous purge is still pending, cannot purge list\n"); + return; + } + + num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN; + num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean; + num_clean = min(blkif->persistent_gnt_c, num_clean); + if ((num_clean == 0) || + (num_clean > (blkif->persistent_gnt_c - atomic_read(&blkif->persistent_gnt_in_use)))) + return; + + /* + * At this point, we can assure that there will be no calls + * to get_persistent_grant (because we are executing this code from + * xen_blkif_schedule), there can only be calls to put_persistent_gnt, + * which means that the number of currently used grants will go down, + * but never up, so we will always be able to remove the requested + * number of grants. + */ + + total = num_clean; + + pr_debug("Going to purge %u persistent grants\n", num_clean); + + BUG_ON(!list_empty(&blkif->persistent_purge_list)); + root = &blkif->persistent_gnts; +purge_list: + foreach_grant_safe(persistent_gnt, n, root, node) { + BUG_ON(persistent_gnt->handle == + BLKBACK_INVALID_HANDLE); + + if (clean_used) { + clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); + continue; + } + + if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) + continue; + if (!scan_used && + (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags))) + continue; + + rb_erase(&persistent_gnt->node, root); + list_add(&persistent_gnt->remove_node, + &blkif->persistent_purge_list); + if (--num_clean == 0) + goto finished; + } + /* + * If we get here it means we also need to start cleaning + * grants that were used since last purge in order to cope + * with the requested num + */ + if (!scan_used && !clean_used) { + pr_debug("Still missing %u purged frames\n", num_clean); + scan_used = true; + goto purge_list; + } +finished: + if (!clean_used) { + pr_debug("Finished scanning for grants to clean, removing used flag\n"); + clean_used = true; + goto purge_list; + } + + blkif->persistent_gnt_c -= (total - num_clean); + blkif->vbd.overflow_max_grants = 0; + + /* We can defer this work */ + schedule_work(&blkif->persistent_purge_work); + pr_debug("Purged %u/%u\n", (total - num_clean), total); + return; +} + +/* + * Retrieve from the 'pending_reqs' a free pending_req structure to be used. + */ +static struct pending_req *alloc_req(struct xen_blkif *blkif) +{ + struct pending_req *req = NULL; + unsigned long flags; + + spin_lock_irqsave(&blkif->pending_free_lock, flags); + if (!list_empty(&blkif->pending_free)) { + req = list_entry(blkif->pending_free.next, struct pending_req, + free_list); + list_del(&req->free_list); + } + spin_unlock_irqrestore(&blkif->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 xen_blkif *blkif, struct pending_req *req) +{ + unsigned long flags; + int was_empty; + + spin_lock_irqsave(&blkif->pending_free_lock, flags); + was_empty = list_empty(&blkif->pending_free); + list_add(&req->free_list, &blkif->pending_free); + spin_unlock_irqrestore(&blkif->pending_free_lock, flags); + if (was_empty) + wake_up(&blkif->pending_free_wq); +} + +/* + * Routines for managing virtual block devices (vbds). + */ +static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif, + int operation) +{ + struct xen_vbd *vbd = &blkif->vbd; + int rc = -EACCES; + + if ((operation != READ) && vbd->readonly) + goto out; + + if (likely(req->nr_sects)) { + blkif_sector_t end = req->sector_number + req->nr_sects; + + if (unlikely(end < req->sector_number)) + goto out; + if (unlikely(end > vbd_sz(vbd))) + goto out; + } + + req->dev = vbd->pdevice; + req->bdev = vbd->bdev; + rc = 0; + + out: + return rc; +} + +static void xen_vbd_resize(struct xen_blkif *blkif) +{ + struct xen_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("VBD Resize: Domid: %d, Device: (%d, %d)\n", + blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice)); + pr_info("VBD Resize: new size %llu\n", new_size); + vbd->size = new_size; +again: + err = xenbus_transaction_start(&xbt); + if (err) { + pr_warn("Error starting transaction\n"); + return; + } + err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu", + (unsigned long long)vbd_sz(vbd)); + if (err) { + pr_warn("Error writing new size\n"); + 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("Error writing the state\n"); + goto abort; + } + + err = xenbus_transaction_end(xbt, 0); + if (err == -EAGAIN) + goto again; + if (err) + pr_warn("Error ending transaction\n"); + return; +abort: + xenbus_transaction_end(xbt, 1); +} + +/* + * Notification from the guest OS. + */ +static void blkif_notify_work(struct xen_blkif *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 xen_blkif *blkif) +{ + pr_info("(%s): oo %3llu | rd %4llu | wr %4llu | f %4llu" + " | ds %4llu | pg: %4u/%4d\n", + current->comm, blkif->st_oo_req, + blkif->st_rd_req, blkif->st_wr_req, + blkif->st_f_req, blkif->st_ds_req, + blkif->persistent_gnt_c, + xen_blkif_max_pgrants); + blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000); + blkif->st_rd_req = 0; + blkif->st_wr_req = 0; + blkif->st_oo_req = 0; + blkif->st_ds_req = 0; +} + +int xen_blkif_schedule(void *arg) +{ + struct xen_blkif *blkif = arg; + struct xen_vbd *vbd = &blkif->vbd; + unsigned long timeout; + int ret; + + xen_blkif_get(blkif); + + while (!kthread_should_stop()) { + if (try_to_freeze()) + continue; + if (unlikely(vbd->size != vbd_sz(vbd))) + xen_vbd_resize(blkif); + + timeout = msecs_to_jiffies(LRU_INTERVAL); + + timeout = wait_event_interruptible_timeout( + blkif->wq, + blkif->waiting_reqs || kthread_should_stop(), + timeout); + if (timeout == 0) + goto purge_gnt_list; + timeout = wait_event_interruptible_timeout( + blkif->pending_free_wq, + !list_empty(&blkif->pending_free) || + kthread_should_stop(), + timeout); + if (timeout == 0) + goto purge_gnt_list; + + blkif->waiting_reqs = 0; + smp_mb(); /* clear flag *before* checking for work */ + + ret = do_block_io_op(blkif); + if (ret > 0) + blkif->waiting_reqs = 1; + if (ret == -EACCES) + wait_event_interruptible(blkif->shutdown_wq, + kthread_should_stop()); + +purge_gnt_list: + if (blkif->vbd.feature_gnt_persistent && + time_after(jiffies, blkif->next_lru)) { + purge_persistent_gnt(blkif); + blkif->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL); + } + + /* Shrink if we have more than xen_blkif_max_buffer_pages */ + shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages); + + if (log_stats && time_after(jiffies, blkif->st_print)) + print_stats(blkif); + } + + /* Drain pending purge work */ + flush_work(&blkif->persistent_purge_work); + + if (log_stats) + print_stats(blkif); + + blkif->xenblkd = NULL; + xen_blkif_put(blkif); + + return 0; +} + +/* + * Remove persistent grants and empty the pool of free pages + */ +void xen_blkbk_free_caches(struct xen_blkif *blkif) +{ + /* Free all persistent grant pages */ + if (!RB_EMPTY_ROOT(&blkif->persistent_gnts)) + free_persistent_gnts(blkif, &blkif->persistent_gnts, + blkif->persistent_gnt_c); + + BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts)); + blkif->persistent_gnt_c = 0; + + /* Since we are shutting down remove all pages from the buffer */ + shrink_free_pagepool(blkif, 0 /* All */); +} + +static unsigned int xen_blkbk_unmap_prepare( + struct xen_blkif *blkif, + struct grant_page **pages, + unsigned int num, + struct gnttab_unmap_grant_ref *unmap_ops, + struct page **unmap_pages) +{ + unsigned int i, invcount = 0; + + for (i = 0; i < num; i++) { + if (pages[i]->persistent_gnt != NULL) { + put_persistent_gnt(blkif, pages[i]->persistent_gnt); + continue; + } + if (pages[i]->handle == BLKBACK_INVALID_HANDLE) + continue; + unmap_pages[invcount] = pages[i]->page; + gnttab_set_unmap_op(&unmap_ops[invcount], vaddr(pages[i]->page), + GNTMAP_host_map, pages[i]->handle); + pages[i]->handle = BLKBACK_INVALID_HANDLE; + invcount++; + } + + return invcount; +} + +static void xen_blkbk_unmap_and_respond_callback(int result, struct gntab_unmap_queue_data *data) +{ + struct pending_req* pending_req = (struct pending_req*) (data->data); + struct xen_blkif *blkif = pending_req->blkif; + + /* BUG_ON used to reproduce existing behaviour, + but is this the best way to deal with this? */ + BUG_ON(result); + + put_free_pages(blkif, data->pages, data->count); + make_response(blkif, pending_req->id, + pending_req->operation, pending_req->status); + free_req(blkif, pending_req); + /* + * Make sure the request is freed before releasing blkif, + * or there could be a race between free_req and the + * cleanup done in xen_blkif_free during shutdown. + * + * NB: The fact that we might try to wake up pending_free_wq + * before drain_complete (in case there's a drain going on) + * it's not a problem with our current implementation + * because we can assure there's no thread waiting on + * pending_free_wq if there's a drain going on, but it has + * to be taken into account if the current model is changed. + */ + if (atomic_dec_and_test(&blkif->inflight) && atomic_read(&blkif->drain)) { + complete(&blkif->drain_complete); + } + xen_blkif_put(blkif); +} + +static void xen_blkbk_unmap_and_respond(struct pending_req *req) +{ + struct gntab_unmap_queue_data* work = &req->gnttab_unmap_data; + struct xen_blkif *blkif = req->blkif; + struct grant_page **pages = req->segments; + unsigned int invcount; + + invcount = xen_blkbk_unmap_prepare(blkif, pages, req->nr_pages, + req->unmap, req->unmap_pages); + + work->data = req; + work->done = xen_blkbk_unmap_and_respond_callback; + work->unmap_ops = req->unmap; + work->kunmap_ops = NULL; + work->pages = req->unmap_pages; + work->count = invcount; + + gnttab_unmap_refs_async(&req->gnttab_unmap_data); +} + + +/* + * Unmap the grant references. + * + * This could accumulate ops up to the batch size to reduce the number + * of hypercalls, but since this is only used in error paths there's + * no real need. + */ +static void xen_blkbk_unmap(struct xen_blkif *blkif, + struct grant_page *pages[], + int num) +{ + struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + unsigned int invcount = 0; + int ret; + + while (num) { + unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST); + + invcount = xen_blkbk_unmap_prepare(blkif, pages, batch, + unmap, unmap_pages); + if (invcount) { + ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount); + BUG_ON(ret); + put_free_pages(blkif, unmap_pages, invcount); + } + pages += batch; + num -= batch; + } +} + +static int xen_blkbk_map(struct xen_blkif *blkif, + struct grant_page *pages[], + int num, bool ro) +{ + struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct persistent_gnt *persistent_gnt = NULL; + phys_addr_t addr = 0; + int i, seg_idx, new_map_idx; + int segs_to_map = 0; + int ret = 0; + int last_map = 0, map_until = 0; + int use_persistent_gnts; + + use_persistent_gnts = (blkif->vbd.feature_gnt_persistent); + + /* + * 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. + */ +again: + for (i = map_until; i < num; i++) { + uint32_t flags; + + if (use_persistent_gnts) + persistent_gnt = get_persistent_gnt( + blkif, + pages[i]->gref); + + if (persistent_gnt) { + /* + * We are using persistent grants and + * the grant is already mapped + */ + pages[i]->page = persistent_gnt->page; + pages[i]->persistent_gnt = persistent_gnt; + } else { + if (get_free_page(blkif, &pages[i]->page)) + goto out_of_memory; + addr = vaddr(pages[i]->page); + pages_to_gnt[segs_to_map] = pages[i]->page; + pages[i]->persistent_gnt = NULL; + flags = GNTMAP_host_map; + if (!use_persistent_gnts && ro) + flags |= GNTMAP_readonly; + gnttab_set_map_op(&map[segs_to_map++], addr, + flags, pages[i]->gref, + blkif->domid); + } + map_until = i + 1; + if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST) + break; + } + + if (segs_to_map) { + ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map); + 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 (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) { + if (!pages[seg_idx]->persistent_gnt) { + /* This is a newly mapped grant */ + BUG_ON(new_map_idx >= segs_to_map); + if (unlikely(map[new_map_idx].status != 0)) { + pr_debug("invalid buffer -- could not remap it\n"); + put_free_pages(blkif, &pages[seg_idx]->page, 1); + pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE; + ret |= 1; + goto next; + } + pages[seg_idx]->handle = map[new_map_idx].handle; + } else { + continue; + } + if (use_persistent_gnts && + blkif->persistent_gnt_c < xen_blkif_max_pgrants) { + /* + * We are using persistent grants, the grant is + * not mapped but we might have room for it. + */ + persistent_gnt = kmalloc(sizeof(struct persistent_gnt), + GFP_KERNEL); + if (!persistent_gnt) { + /* + * If we don't have enough memory to + * allocate the persistent_gnt struct + * map this grant non-persistenly + */ + goto next; + } + persistent_gnt->gnt = map[new_map_idx].ref; + persistent_gnt->handle = map[new_map_idx].handle; + persistent_gnt->page = pages[seg_idx]->page; + if (add_persistent_gnt(blkif, + persistent_gnt)) { + kfree(persistent_gnt); + persistent_gnt = NULL; + goto next; + } + pages[seg_idx]->persistent_gnt = persistent_gnt; + pr_debug("grant %u added to the tree of persistent grants, using %u/%u\n", + persistent_gnt->gnt, blkif->persistent_gnt_c, + xen_blkif_max_pgrants); + goto next; + } + if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) { + blkif->vbd.overflow_max_grants = 1; + pr_debug("domain %u, device %#x is using maximum number of persistent grants\n", + blkif->domid, blkif->vbd.handle); + } + /* + * We could not map this grant persistently, so use it as + * a non-persistent grant. + */ +next: + new_map_idx++; + } + segs_to_map = 0; + last_map = map_until; + if (map_until != num) + goto again; + + return ret; + +out_of_memory: + pr_alert("%s: out of memory\n", __func__); + put_free_pages(blkif, pages_to_gnt, segs_to_map); + return -ENOMEM; +} + +static int xen_blkbk_map_seg(struct pending_req *pending_req) +{ + int rc; + + rc = xen_blkbk_map(pending_req->blkif, pending_req->segments, + pending_req->nr_pages, + (pending_req->operation != BLKIF_OP_READ)); + + return rc; +} + +static int xen_blkbk_parse_indirect(struct blkif_request *req, + struct pending_req *pending_req, + struct seg_buf seg[], + struct phys_req *preq) +{ + struct grant_page **pages = pending_req->indirect_pages; + struct xen_blkif *blkif = pending_req->blkif; + int indirect_grefs, rc, n, nseg, i; + struct blkif_request_segment *segments = NULL; + + nseg = pending_req->nr_pages; + indirect_grefs = INDIRECT_PAGES(nseg); + BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST); + + for (i = 0; i < indirect_grefs; i++) + pages[i]->gref = req->u.indirect.indirect_grefs[i]; + + rc = xen_blkbk_map(blkif, pages, indirect_grefs, true); + if (rc) + goto unmap; + + for (n = 0, i = 0; n < nseg; n++) { + if ((n % SEGS_PER_INDIRECT_FRAME) == 0) { + /* Map indirect segments */ + if (segments) + kunmap_atomic(segments); + segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page); + } + i = n % SEGS_PER_INDIRECT_FRAME; + pending_req->segments[n]->gref = segments[i].gref; + seg[n].nsec = segments[i].last_sect - + segments[i].first_sect + 1; + seg[n].offset = (segments[i].first_sect << 9); + if ((segments[i].last_sect >= (PAGE_SIZE >> 9)) || + (segments[i].last_sect < segments[i].first_sect)) { + rc = -EINVAL; + goto unmap; + } + preq->nr_sects += seg[n].nsec; + } + +unmap: + if (segments) + kunmap_atomic(segments); + xen_blkbk_unmap(blkif, pages, indirect_grefs); + return rc; +} + +static int dispatch_discard_io(struct xen_blkif *blkif, + struct blkif_request *req) +{ + int err = 0; + int status = BLKIF_RSP_OKAY; + struct block_device *bdev = blkif->vbd.bdev; + unsigned long secure; + struct phys_req preq; + + xen_blkif_get(blkif); + + preq.sector_number = req->u.discard.sector_number; + preq.nr_sects = req->u.discard.nr_sectors; + + err = xen_vbd_translate(&preq, blkif, WRITE); + if (err) { + pr_warn("access denied: DISCARD [%llu->%llu] on dev=%04x\n", + preq.sector_number, + preq.sector_number + preq.nr_sects, blkif->vbd.pdevice); + goto fail_response; + } + blkif->st_ds_req++; + + secure = (blkif->vbd.discard_secure && + (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ? + BLKDEV_DISCARD_SECURE : 0; + + err = blkdev_issue_discard(bdev, req->u.discard.sector_number, + req->u.discard.nr_sectors, + GFP_KERNEL, secure); +fail_response: + if (err == -EOPNOTSUPP) { + pr_debug("discard op failed, not supported\n"); + status = BLKIF_RSP_EOPNOTSUPP; + } else if (err) + status = BLKIF_RSP_ERROR; + + make_response(blkif, req->u.discard.id, req->operation, status); + xen_blkif_put(blkif); + return err; +} + +static int dispatch_other_io(struct xen_blkif *blkif, + struct blkif_request *req, + struct pending_req *pending_req) +{ + free_req(blkif, pending_req); + make_response(blkif, req->u.other.id, req->operation, + BLKIF_RSP_EOPNOTSUPP); + return -EIO; +} + +static void xen_blk_drain_io(struct xen_blkif *blkif) +{ + atomic_set(&blkif->drain, 1); + do { + if (atomic_read(&blkif->inflight) == 0) + break; + wait_for_completion_interruptible_timeout( + &blkif->drain_complete, HZ); + + if (!atomic_read(&blkif->drain)) + break; + } while (!kthread_should_stop()); + atomic_set(&blkif->drain, 0); +} + +/* + * 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("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 ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) && + (error == -EOPNOTSUPP)) { + pr_debug("write barrier op failed, not supported\n"); + xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0); + pending_req->status = BLKIF_RSP_EOPNOTSUPP; + } else if (error) { + pr_debug("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_and_respond(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 xen_blkif *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'. */ + + if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) { + rc = blk_rings->common.rsp_prod_pvt; + pr_warn("Frontend provided bogus ring requests (%d - %d = %d). Halting ring processing on dev=%04x\n", + rp, rc, rp - rc, blkif->vbd.pdevice); + return -EACCES; + } + 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(blkif); + 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(); + + switch (req.operation) { + case BLKIF_OP_READ: + case BLKIF_OP_WRITE: + case BLKIF_OP_WRITE_BARRIER: + case BLKIF_OP_FLUSH_DISKCACHE: + case BLKIF_OP_INDIRECT: + if (dispatch_rw_block_io(blkif, &req, pending_req)) + goto done; + break; + case BLKIF_OP_DISCARD: + free_req(blkif, pending_req); + if (dispatch_discard_io(blkif, &req)) + goto done; + break; + default: + if (dispatch_other_io(blkif, &req, pending_req)) + goto done; + break; + } + + /* Yield point for this unbounded loop. */ + cond_resched(); + } +done: + return more_to_do; +} + +static int +do_block_io_op(struct xen_blkif *blkif) +{ + union blkif_back_rings *blk_rings = &blkif->blk_rings; + int more_to_do; + + do { + more_to_do = __do_block_io_op(blkif); + if (more_to_do) + break; + + RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do); + } while (more_to_do); + + 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 xen_blkif *blkif, + struct blkif_request *req, + struct pending_req *pending_req) +{ + struct phys_req preq; + struct seg_buf *seg = pending_req->seg; + unsigned int nseg; + struct bio *bio = NULL; + struct bio **biolist = pending_req->biolist; + int i, nbio = 0; + int operation; + struct blk_plug plug; + bool drain = false; + struct grant_page **pages = pending_req->segments; + unsigned short req_operation; + + req_operation = req->operation == BLKIF_OP_INDIRECT ? + req->u.indirect.indirect_op : req->operation; + if ((req->operation == BLKIF_OP_INDIRECT) && + (req_operation != BLKIF_OP_READ) && + (req_operation != BLKIF_OP_WRITE)) { + pr_debug("Invalid indirect operation (%u)\n", req_operation); + goto fail_response; + } + + 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_WRITE_BARRIER: + drain = true; + case BLKIF_OP_FLUSH_DISKCACHE: + blkif->st_f_req++; + operation = WRITE_FLUSH; + break; + default: + operation = 0; /* make gcc happy */ + goto fail_response; + break; + } + + /* Check that the number of segments is sane. */ + nseg = req->operation == BLKIF_OP_INDIRECT ? + req->u.indirect.nr_segments : req->u.rw.nr_segments; + + if (unlikely(nseg == 0 && operation != WRITE_FLUSH) || + unlikely((req->operation != BLKIF_OP_INDIRECT) && + (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) || + unlikely((req->operation == BLKIF_OP_INDIRECT) && + (nseg > MAX_INDIRECT_SEGMENTS))) { + pr_debug("Bad number of segments in request (%d)\n", nseg); + /* Haven't submitted any bio's yet. */ + goto fail_response; + } + + preq.nr_sects = 0; + + pending_req->blkif = blkif; + pending_req->id = req->u.rw.id; + pending_req->operation = req_operation; + pending_req->status = BLKIF_RSP_OKAY; + pending_req->nr_pages = nseg; + + if (req->operation != BLKIF_OP_INDIRECT) { + preq.dev = req->u.rw.handle; + preq.sector_number = req->u.rw.sector_number; + for (i = 0; i < nseg; i++) { + pages[i]->gref = req->u.rw.seg[i].gref; + seg[i].nsec = req->u.rw.seg[i].last_sect - + req->u.rw.seg[i].first_sect + 1; + seg[i].offset = (req->u.rw.seg[i].first_sect << 9); + 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; + } + } else { + preq.dev = req->u.indirect.handle; + preq.sector_number = req->u.indirect.sector_number; + if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq)) + goto fail_response; + } + + if (xen_vbd_translate(&preq, blkif, operation) != 0) { + pr_debug("access denied: %s of [%llu,%llu] on dev=%04x\n", + operation == READ ? "read" : "write", + preq.sector_number, + preq.sector_number + preq.nr_sects, + blkif->vbd.pdevice); + goto fail_response; + } + + /* + * This check _MUST_ be done after xen_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("Misaligned I/O request from domain %d\n", + blkif->domid); + goto fail_response; + } + } + + /* Wait on all outstanding I/O's and once that has been completed + * issue the WRITE_FLUSH. + */ + if (drain) + xen_blk_drain_io(pending_req->blkif); + + /* + * 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_seg(pending_req)) + goto fail_flush; + + /* + * This corresponding xen_blkif_put is done in __end_block_io_op, or + * below (in "!bio") if we are handling a BLKIF_OP_DISCARD. + */ + xen_blkif_get(blkif); + atomic_inc(&blkif->inflight); + + for (i = 0; i < nseg; i++) { + while ((bio == NULL) || + (bio_add_page(bio, + pages[i]->page, + seg[i].nsec << 9, + seg[i].offset) == 0)) { + + int nr_iovecs = min_t(int, (nseg-i), BIO_MAX_PAGES); + bio = bio_alloc(GFP_KERNEL, nr_iovecs); + if (unlikely(bio == NULL)) + goto fail_put_bio; + + biolist[nbio++] = bio; + bio->bi_bdev = preq.bdev; + bio->bi_private = pending_req; + bio->bi_end_io = end_block_io_op; + bio->bi_iter.bi_sector = preq.sector_number; + } + + preq.sector_number += seg[i].nsec; + } + + /* This will be hit if the operation was a flush or discard. */ + if (!bio) { + BUG_ON(operation != WRITE_FLUSH); + + bio = bio_alloc(GFP_KERNEL, 0); + if (unlikely(bio == NULL)) + goto fail_put_bio; + + biolist[nbio++] = bio; + bio->bi_bdev = preq.bdev; + bio->bi_private = pending_req; + bio->bi_end_io = end_block_io_op; + } + + atomic_set(&pending_req->pendcnt, nbio); + 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) + blkif->st_wr_sect += preq.nr_sects; + + return 0; + + fail_flush: + xen_blkbk_unmap(blkif, pending_req->segments, + pending_req->nr_pages); + fail_response: + /* Haven't submitted any bio's yet. */ + make_response(blkif, req->u.rw.id, req_operation, BLKIF_RSP_ERROR); + free_req(blkif, pending_req); + msleep(1); /* back off a bit */ + return -EIO; + + fail_put_bio: + for (i = 0; i < nbio; i++) + bio_put(biolist[i]); + atomic_set(&pending_req->pendcnt, 1); + __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 xen_blkif *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 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); + spin_unlock_irqrestore(&blkif->blk_ring_lock, flags); + if (notify) + notify_remote_via_irq(blkif->irq); +} + +static int __init xen_blkif_init(void) +{ + int rc = 0; + + if (!xen_domain()) + return -ENODEV; + + rc = xen_blkif_interface_init(); + if (rc) + goto failed_init; + + rc = xen_blkif_xenbus_init(); + if (rc) + goto failed_init; + + failed_init: + return rc; +} + +module_init(xen_blkif_init); + +MODULE_LICENSE("Dual BSD/GPL"); +MODULE_ALIAS("xen-backend:vbd"); |