1 /******************************************************************************
3 * Back-end of the driver for virtual block devices. This portion of the
4 * driver exports a 'unified' block-device interface that can be accessed
5 * by any operating system that implements a compatible front end. A
6 * reference front-end implementation can be found in:
7 * drivers/block/xen-blkfront.c
9 * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
10 * Copyright (c) 2005, Christopher Clark
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License version 2
14 * as published by the Free Software Foundation; or, when distributed
15 * separately from the Linux kernel or incorporated into other
16 * software packages, subject to the following license:
18 * Permission is hereby granted, free of charge, to any person obtaining a copy
19 * of this source file (the "Software"), to deal in the Software without
20 * restriction, including without limitation the rights to use, copy, modify,
21 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
22 * and to permit persons to whom the Software is furnished to do so, subject to
23 * the following conditions:
25 * The above copyright notice and this permission notice shall be included in
26 * all copies or substantial portions of the Software.
28 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
29 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
30 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
31 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
32 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
33 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
37 #define pr_fmt(fmt) "xen-blkback: " fmt
39 #include <linux/spinlock.h>
40 #include <linux/kthread.h>
41 #include <linux/list.h>
42 #include <linux/delay.h>
43 #include <linux/freezer.h>
44 #include <linux/bitmap.h>
46 #include <xen/events.h>
49 #include <asm/xen/hypervisor.h>
50 #include <asm/xen/hypercall.h>
51 #include <xen/balloon.h>
52 #include <xen/grant_table.h>
56 * Maximum number of unused free pages to keep in the internal buffer.
57 * Setting this to a value too low will reduce memory used in each backend,
58 * but can have a performance penalty.
60 * A sane value is xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST, but can
61 * be set to a lower value that might degrade performance on some intensive
65 static int xen_blkif_max_buffer_pages = 1024;
66 module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644);
67 MODULE_PARM_DESC(max_buffer_pages,
68 "Maximum number of free pages to keep in each block backend buffer");
71 * Maximum number of grants to map persistently in blkback. For maximum
72 * performance this should be the total numbers of grants that can be used
73 * to fill the ring, but since this might become too high, specially with
74 * the use of indirect descriptors, we set it to a value that provides good
75 * performance without using too much memory.
77 * When the list of persistent grants is full we clean it up using a LRU
81 static int xen_blkif_max_pgrants = 1056;
82 module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644);
83 MODULE_PARM_DESC(max_persistent_grants,
84 "Maximum number of grants to map persistently");
87 * Maximum number of rings/queues blkback supports, allow as many queues as there
88 * are CPUs if user has not specified a value.
90 unsigned int xenblk_max_queues;
91 module_param_named(max_queues, xenblk_max_queues, uint, 0644);
92 MODULE_PARM_DESC(max_queues,
93 "Maximum number of hardware queues per virtual disk." \
94 "By default it is the number of online CPUs.");
97 * Maximum order of pages to be used for the shared ring between front and
98 * backend, 4KB page granularity is used.
100 unsigned int xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;
101 module_param_named(max_ring_page_order, xen_blkif_max_ring_order, int, S_IRUGO);
102 MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the shared ring");
104 * The LRU mechanism to clean the lists of persistent grants needs to
105 * be executed periodically. The time interval between consecutive executions
106 * of the purge mechanism is set in ms.
108 #define LRU_INTERVAL 100
111 * When the persistent grants list is full we will remove unused grants
112 * from the list. The percent number of grants to be removed at each LRU
115 #define LRU_PERCENT_CLEAN 5
117 /* Run-time switchable: /sys/module/blkback/parameters/ */
118 static unsigned int log_stats;
119 module_param(log_stats, int, 0644);
121 #define BLKBACK_INVALID_HANDLE (~0)
123 /* Number of free pages to remove on each call to gnttab_free_pages */
124 #define NUM_BATCH_FREE_PAGES 10
126 static inline int get_free_page(struct xen_blkif_ring *ring, struct page **page)
130 spin_lock_irqsave(&ring->free_pages_lock, flags);
131 if (list_empty(&ring->free_pages)) {
132 BUG_ON(ring->free_pages_num != 0);
133 spin_unlock_irqrestore(&ring->free_pages_lock, flags);
134 return gnttab_alloc_pages(1, page);
136 BUG_ON(ring->free_pages_num == 0);
137 page[0] = list_first_entry(&ring->free_pages, struct page, lru);
138 list_del(&page[0]->lru);
139 ring->free_pages_num--;
140 spin_unlock_irqrestore(&ring->free_pages_lock, flags);
145 static inline void put_free_pages(struct xen_blkif_ring *ring, struct page **page,
151 spin_lock_irqsave(&ring->free_pages_lock, flags);
152 for (i = 0; i < num; i++)
153 list_add(&page[i]->lru, &ring->free_pages);
154 ring->free_pages_num += num;
155 spin_unlock_irqrestore(&ring->free_pages_lock, flags);
158 static inline void shrink_free_pagepool(struct xen_blkif_ring *ring, int num)
160 /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */
161 struct page *page[NUM_BATCH_FREE_PAGES];
162 unsigned int num_pages = 0;
165 spin_lock_irqsave(&ring->free_pages_lock, flags);
166 while (ring->free_pages_num > num) {
167 BUG_ON(list_empty(&ring->free_pages));
168 page[num_pages] = list_first_entry(&ring->free_pages,
170 list_del(&page[num_pages]->lru);
171 ring->free_pages_num--;
172 if (++num_pages == NUM_BATCH_FREE_PAGES) {
173 spin_unlock_irqrestore(&ring->free_pages_lock, flags);
174 gnttab_free_pages(num_pages, page);
175 spin_lock_irqsave(&ring->free_pages_lock, flags);
179 spin_unlock_irqrestore(&ring->free_pages_lock, flags);
181 gnttab_free_pages(num_pages, page);
184 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
186 static int do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags);
187 static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
188 struct blkif_request *req,
189 struct pending_req *pending_req);
190 static void make_response(struct xen_blkif_ring *ring, u64 id,
191 unsigned short op, int st);
193 #define foreach_grant_safe(pos, n, rbtree, node) \
194 for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
195 (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
196 &(pos)->node != NULL; \
197 (pos) = container_of(n, typeof(*(pos)), node), \
198 (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
202 * We don't need locking around the persistent grant helpers
203 * because blkback uses a single-thread for each backend, so we
204 * can be sure that this functions will never be called recursively.
206 * The only exception to that is put_persistent_grant, that can be called
207 * from interrupt context (by xen_blkbk_unmap), so we have to use atomic
208 * bit operations to modify the flags of a persistent grant and to count
209 * the number of used grants.
211 static int add_persistent_gnt(struct xen_blkif_ring *ring,
212 struct persistent_gnt *persistent_gnt)
214 struct rb_node **new = NULL, *parent = NULL;
215 struct persistent_gnt *this;
216 struct xen_blkif *blkif = ring->blkif;
218 if (ring->persistent_gnt_c >= xen_blkif_max_pgrants) {
219 if (!blkif->vbd.overflow_max_grants)
220 blkif->vbd.overflow_max_grants = 1;
223 /* Figure out where to put new node */
224 new = &ring->persistent_gnts.rb_node;
226 this = container_of(*new, struct persistent_gnt, node);
229 if (persistent_gnt->gnt < this->gnt)
230 new = &((*new)->rb_left);
231 else if (persistent_gnt->gnt > this->gnt)
232 new = &((*new)->rb_right);
234 pr_alert_ratelimited("trying to add a gref that's already in the tree\n");
239 bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE);
240 set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
241 /* Add new node and rebalance tree. */
242 rb_link_node(&(persistent_gnt->node), parent, new);
243 rb_insert_color(&(persistent_gnt->node), &ring->persistent_gnts);
244 ring->persistent_gnt_c++;
245 atomic_inc(&ring->persistent_gnt_in_use);
249 static struct persistent_gnt *get_persistent_gnt(struct xen_blkif_ring *ring,
252 struct persistent_gnt *data;
253 struct rb_node *node = NULL;
255 node = ring->persistent_gnts.rb_node;
257 data = container_of(node, struct persistent_gnt, node);
259 if (gref < data->gnt)
260 node = node->rb_left;
261 else if (gref > data->gnt)
262 node = node->rb_right;
264 if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) {
265 pr_alert_ratelimited("requesting a grant already in use\n");
268 set_bit(PERSISTENT_GNT_ACTIVE, data->flags);
269 atomic_inc(&ring->persistent_gnt_in_use);
276 static void put_persistent_gnt(struct xen_blkif_ring *ring,
277 struct persistent_gnt *persistent_gnt)
279 if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
280 pr_alert_ratelimited("freeing a grant already unused\n");
281 set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
282 clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
283 atomic_dec(&ring->persistent_gnt_in_use);
286 static void free_persistent_gnts(struct xen_blkif_ring *ring, struct rb_root *root,
289 struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
290 struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
291 struct persistent_gnt *persistent_gnt;
293 int segs_to_unmap = 0;
294 struct gntab_unmap_queue_data unmap_data;
296 unmap_data.pages = pages;
297 unmap_data.unmap_ops = unmap;
298 unmap_data.kunmap_ops = NULL;
300 foreach_grant_safe(persistent_gnt, n, root, node) {
301 BUG_ON(persistent_gnt->handle ==
302 BLKBACK_INVALID_HANDLE);
303 gnttab_set_unmap_op(&unmap[segs_to_unmap],
304 (unsigned long) pfn_to_kaddr(page_to_pfn(
305 persistent_gnt->page)),
307 persistent_gnt->handle);
309 pages[segs_to_unmap] = persistent_gnt->page;
311 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
312 !rb_next(&persistent_gnt->node)) {
314 unmap_data.count = segs_to_unmap;
315 BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
317 put_free_pages(ring, pages, segs_to_unmap);
321 rb_erase(&persistent_gnt->node, root);
322 kfree(persistent_gnt);
328 void xen_blkbk_unmap_purged_grants(struct work_struct *work)
330 struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
331 struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
332 struct persistent_gnt *persistent_gnt;
333 int segs_to_unmap = 0;
334 struct xen_blkif_ring *ring = container_of(work, typeof(*ring), persistent_purge_work);
335 struct gntab_unmap_queue_data unmap_data;
337 unmap_data.pages = pages;
338 unmap_data.unmap_ops = unmap;
339 unmap_data.kunmap_ops = NULL;
341 while(!list_empty(&ring->persistent_purge_list)) {
342 persistent_gnt = list_first_entry(&ring->persistent_purge_list,
343 struct persistent_gnt,
345 list_del(&persistent_gnt->remove_node);
347 gnttab_set_unmap_op(&unmap[segs_to_unmap],
348 vaddr(persistent_gnt->page),
350 persistent_gnt->handle);
352 pages[segs_to_unmap] = persistent_gnt->page;
354 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
355 unmap_data.count = segs_to_unmap;
356 BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
357 put_free_pages(ring, pages, segs_to_unmap);
360 kfree(persistent_gnt);
362 if (segs_to_unmap > 0) {
363 unmap_data.count = segs_to_unmap;
364 BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
365 put_free_pages(ring, pages, segs_to_unmap);
369 static void purge_persistent_gnt(struct xen_blkif_ring *ring)
371 struct persistent_gnt *persistent_gnt;
373 unsigned int num_clean, total;
374 bool scan_used = false, clean_used = false;
375 struct rb_root *root;
377 if (ring->persistent_gnt_c < xen_blkif_max_pgrants ||
378 (ring->persistent_gnt_c == xen_blkif_max_pgrants &&
379 !ring->blkif->vbd.overflow_max_grants)) {
383 if (work_busy(&ring->persistent_purge_work)) {
384 pr_alert_ratelimited("Scheduled work from previous purge is still busy, cannot purge list\n");
388 num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN;
389 num_clean = ring->persistent_gnt_c - xen_blkif_max_pgrants + num_clean;
390 num_clean = min(ring->persistent_gnt_c, num_clean);
391 if ((num_clean == 0) ||
392 (num_clean > (ring->persistent_gnt_c - atomic_read(&ring->persistent_gnt_in_use))))
396 * At this point, we can assure that there will be no calls
397 * to get_persistent_grant (because we are executing this code from
398 * xen_blkif_schedule), there can only be calls to put_persistent_gnt,
399 * which means that the number of currently used grants will go down,
400 * but never up, so we will always be able to remove the requested
406 pr_debug("Going to purge %u persistent grants\n", num_clean);
408 BUG_ON(!list_empty(&ring->persistent_purge_list));
409 root = &ring->persistent_gnts;
411 foreach_grant_safe(persistent_gnt, n, root, node) {
412 BUG_ON(persistent_gnt->handle ==
413 BLKBACK_INVALID_HANDLE);
416 clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
420 if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
423 (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags)))
426 rb_erase(&persistent_gnt->node, root);
427 list_add(&persistent_gnt->remove_node,
428 &ring->persistent_purge_list);
429 if (--num_clean == 0)
433 * If we get here it means we also need to start cleaning
434 * grants that were used since last purge in order to cope
435 * with the requested num
437 if (!scan_used && !clean_used) {
438 pr_debug("Still missing %u purged frames\n", num_clean);
444 pr_debug("Finished scanning for grants to clean, removing used flag\n");
449 ring->persistent_gnt_c -= (total - num_clean);
450 ring->blkif->vbd.overflow_max_grants = 0;
452 /* We can defer this work */
453 schedule_work(&ring->persistent_purge_work);
454 pr_debug("Purged %u/%u\n", (total - num_clean), total);
461 * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
463 static struct pending_req *alloc_req(struct xen_blkif_ring *ring)
465 struct pending_req *req = NULL;
468 spin_lock_irqsave(&ring->pending_free_lock, flags);
469 if (!list_empty(&ring->pending_free)) {
470 req = list_entry(ring->pending_free.next, struct pending_req,
472 list_del(&req->free_list);
474 spin_unlock_irqrestore(&ring->pending_free_lock, flags);
479 * Return the 'pending_req' structure back to the freepool. We also
480 * wake up the thread if it was waiting for a free page.
482 static void free_req(struct xen_blkif_ring *ring, struct pending_req *req)
487 spin_lock_irqsave(&ring->pending_free_lock, flags);
488 was_empty = list_empty(&ring->pending_free);
489 list_add(&req->free_list, &ring->pending_free);
490 spin_unlock_irqrestore(&ring->pending_free_lock, flags);
492 wake_up(&ring->pending_free_wq);
496 * Routines for managing virtual block devices (vbds).
498 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
501 struct xen_vbd *vbd = &blkif->vbd;
504 if ((operation != REQ_OP_READ) && vbd->readonly)
507 if (likely(req->nr_sects)) {
508 blkif_sector_t end = req->sector_number + req->nr_sects;
510 if (unlikely(end < req->sector_number))
512 if (unlikely(end > vbd_sz(vbd)))
516 req->dev = vbd->pdevice;
517 req->bdev = vbd->bdev;
524 static void xen_vbd_resize(struct xen_blkif *blkif)
526 struct xen_vbd *vbd = &blkif->vbd;
527 struct xenbus_transaction xbt;
529 struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
530 unsigned long long new_size = vbd_sz(vbd);
532 pr_info("VBD Resize: Domid: %d, Device: (%d, %d)\n",
533 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
534 pr_info("VBD Resize: new size %llu\n", new_size);
535 vbd->size = new_size;
537 err = xenbus_transaction_start(&xbt);
539 pr_warn("Error starting transaction\n");
542 err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
543 (unsigned long long)vbd_sz(vbd));
545 pr_warn("Error writing new size\n");
549 * Write the current state; we will use this to synchronize
550 * the front-end. If the current state is "connected" the
551 * front-end will get the new size information online.
553 err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
555 pr_warn("Error writing the state\n");
559 err = xenbus_transaction_end(xbt, 0);
563 pr_warn("Error ending transaction\n");
566 xenbus_transaction_end(xbt, 1);
570 * Notification from the guest OS.
572 static void blkif_notify_work(struct xen_blkif_ring *ring)
574 ring->waiting_reqs = 1;
578 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
580 blkif_notify_work(dev_id);
585 * SCHEDULER FUNCTIONS
588 static void print_stats(struct xen_blkif_ring *ring)
590 pr_info("(%s): oo %3llu | rd %4llu | wr %4llu | f %4llu"
591 " | ds %4llu | pg: %4u/%4d\n",
592 current->comm, ring->st_oo_req,
593 ring->st_rd_req, ring->st_wr_req,
594 ring->st_f_req, ring->st_ds_req,
595 ring->persistent_gnt_c,
596 xen_blkif_max_pgrants);
597 ring->st_print = jiffies + msecs_to_jiffies(10 * 1000);
604 int xen_blkif_schedule(void *arg)
606 struct xen_blkif_ring *ring = arg;
607 struct xen_blkif *blkif = ring->blkif;
608 struct xen_vbd *vbd = &blkif->vbd;
609 unsigned long timeout;
612 unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;
615 while (!kthread_should_stop()) {
618 if (unlikely(vbd->size != vbd_sz(vbd)))
619 xen_vbd_resize(blkif);
621 timeout = msecs_to_jiffies(LRU_INTERVAL);
623 timeout = wait_event_interruptible_timeout(
625 ring->waiting_reqs || kthread_should_stop(),
629 timeout = wait_event_interruptible_timeout(
630 ring->pending_free_wq,
631 !list_empty(&ring->pending_free) ||
632 kthread_should_stop(),
637 do_eoi = ring->waiting_reqs;
639 ring->waiting_reqs = 0;
640 smp_mb(); /* clear flag *before* checking for work */
642 ret = do_block_io_op(ring, &eoi_flags);
644 ring->waiting_reqs = 1;
646 wait_event_interruptible(ring->shutdown_wq,
647 kthread_should_stop());
649 if (do_eoi && !ring->waiting_reqs) {
650 xen_irq_lateeoi(ring->irq, eoi_flags);
651 eoi_flags |= XEN_EOI_FLAG_SPURIOUS;
655 if (blkif->vbd.feature_gnt_persistent &&
656 time_after(jiffies, ring->next_lru)) {
657 purge_persistent_gnt(ring);
658 ring->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL);
661 /* Shrink if we have more than xen_blkif_max_buffer_pages */
662 shrink_free_pagepool(ring, xen_blkif_max_buffer_pages);
664 if (log_stats && time_after(jiffies, ring->st_print))
668 /* Drain pending purge work */
669 flush_work(&ring->persistent_purge_work);
674 ring->xenblkd = NULL;
680 * Remove persistent grants and empty the pool of free pages
682 void xen_blkbk_free_caches(struct xen_blkif_ring *ring)
684 /* Free all persistent grant pages */
685 if (!RB_EMPTY_ROOT(&ring->persistent_gnts))
686 free_persistent_gnts(ring, &ring->persistent_gnts,
687 ring->persistent_gnt_c);
689 BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
690 ring->persistent_gnt_c = 0;
692 /* Since we are shutting down remove all pages from the buffer */
693 shrink_free_pagepool(ring, 0 /* All */);
696 static unsigned int xen_blkbk_unmap_prepare(
697 struct xen_blkif_ring *ring,
698 struct grant_page **pages,
700 struct gnttab_unmap_grant_ref *unmap_ops,
701 struct page **unmap_pages)
703 unsigned int i, invcount = 0;
705 for (i = 0; i < num; i++) {
706 if (pages[i]->persistent_gnt != NULL) {
707 put_persistent_gnt(ring, pages[i]->persistent_gnt);
710 if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
712 unmap_pages[invcount] = pages[i]->page;
713 gnttab_set_unmap_op(&unmap_ops[invcount], vaddr(pages[i]->page),
714 GNTMAP_host_map, pages[i]->handle);
715 pages[i]->handle = BLKBACK_INVALID_HANDLE;
722 static void xen_blkbk_unmap_and_respond_callback(int result, struct gntab_unmap_queue_data *data)
724 struct pending_req *pending_req = (struct pending_req *)(data->data);
725 struct xen_blkif_ring *ring = pending_req->ring;
726 struct xen_blkif *blkif = ring->blkif;
728 /* BUG_ON used to reproduce existing behaviour,
729 but is this the best way to deal with this? */
732 put_free_pages(ring, data->pages, data->count);
733 make_response(ring, pending_req->id,
734 pending_req->operation, pending_req->status);
735 free_req(ring, pending_req);
737 * Make sure the request is freed before releasing blkif,
738 * or there could be a race between free_req and the
739 * cleanup done in xen_blkif_free during shutdown.
741 * NB: The fact that we might try to wake up pending_free_wq
742 * before drain_complete (in case there's a drain going on)
743 * it's not a problem with our current implementation
744 * because we can assure there's no thread waiting on
745 * pending_free_wq if there's a drain going on, but it has
746 * to be taken into account if the current model is changed.
748 if (atomic_dec_and_test(&ring->inflight) && atomic_read(&blkif->drain)) {
749 complete(&blkif->drain_complete);
751 xen_blkif_put(blkif);
754 static void xen_blkbk_unmap_and_respond(struct pending_req *req)
756 struct gntab_unmap_queue_data* work = &req->gnttab_unmap_data;
757 struct xen_blkif_ring *ring = req->ring;
758 struct grant_page **pages = req->segments;
759 unsigned int invcount;
761 invcount = xen_blkbk_unmap_prepare(ring, pages, req->nr_segs,
762 req->unmap, req->unmap_pages);
765 work->done = xen_blkbk_unmap_and_respond_callback;
766 work->unmap_ops = req->unmap;
767 work->kunmap_ops = NULL;
768 work->pages = req->unmap_pages;
769 work->count = invcount;
771 gnttab_unmap_refs_async(&req->gnttab_unmap_data);
776 * Unmap the grant references.
778 * This could accumulate ops up to the batch size to reduce the number
779 * of hypercalls, but since this is only used in error paths there's
782 static void xen_blkbk_unmap(struct xen_blkif_ring *ring,
783 struct grant_page *pages[],
786 struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
787 struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
788 unsigned int invcount = 0;
792 unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST);
794 invcount = xen_blkbk_unmap_prepare(ring, pages, batch,
797 ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
799 put_free_pages(ring, unmap_pages, invcount);
806 static int xen_blkbk_map(struct xen_blkif_ring *ring,
807 struct grant_page *pages[],
810 struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
811 struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
812 struct persistent_gnt *persistent_gnt = NULL;
813 phys_addr_t addr = 0;
814 int i, seg_idx, new_map_idx;
817 int last_map = 0, map_until = 0;
818 int use_persistent_gnts;
819 struct xen_blkif *blkif = ring->blkif;
821 use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
824 * Fill out preq.nr_sects with proper amount of sectors, and setup
825 * assign map[..] with the PFN of the page in our domain with the
826 * corresponding grant reference for each page.
829 for (i = map_until; i < num; i++) {
832 if (use_persistent_gnts) {
833 persistent_gnt = get_persistent_gnt(
838 if (persistent_gnt) {
840 * We are using persistent grants and
841 * the grant is already mapped
843 pages[i]->page = persistent_gnt->page;
844 pages[i]->persistent_gnt = persistent_gnt;
846 if (get_free_page(ring, &pages[i]->page)) {
847 put_free_pages(ring, pages_to_gnt, segs_to_map);
851 addr = vaddr(pages[i]->page);
852 pages_to_gnt[segs_to_map] = pages[i]->page;
853 pages[i]->persistent_gnt = NULL;
854 flags = GNTMAP_host_map;
855 if (!use_persistent_gnts && ro)
856 flags |= GNTMAP_readonly;
857 gnttab_set_map_op(&map[segs_to_map++], addr,
858 flags, pages[i]->gref,
862 if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
867 ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
870 * Now swizzle the MFN in our domain with the MFN from the other domain
871 * so that when we access vaddr(pending_req,i) it has the contents of
872 * the page from the other domain.
874 for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) {
875 if (!pages[seg_idx]->persistent_gnt) {
876 /* This is a newly mapped grant */
877 BUG_ON(new_map_idx >= segs_to_map);
878 if (unlikely(map[new_map_idx].status != 0)) {
879 pr_debug("invalid buffer -- could not remap it\n");
880 put_free_pages(ring, &pages[seg_idx]->page, 1);
881 pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
885 pages[seg_idx]->handle = map[new_map_idx].handle;
889 if (use_persistent_gnts &&
890 ring->persistent_gnt_c < xen_blkif_max_pgrants) {
892 * We are using persistent grants, the grant is
893 * not mapped but we might have room for it.
895 persistent_gnt = kmalloc(sizeof(struct persistent_gnt),
897 if (!persistent_gnt) {
899 * If we don't have enough memory to
900 * allocate the persistent_gnt struct
901 * map this grant non-persistenly
905 persistent_gnt->gnt = map[new_map_idx].ref;
906 persistent_gnt->handle = map[new_map_idx].handle;
907 persistent_gnt->page = pages[seg_idx]->page;
908 if (add_persistent_gnt(ring,
910 kfree(persistent_gnt);
911 persistent_gnt = NULL;
914 pages[seg_idx]->persistent_gnt = persistent_gnt;
915 pr_debug("grant %u added to the tree of persistent grants, using %u/%u\n",
916 persistent_gnt->gnt, ring->persistent_gnt_c,
917 xen_blkif_max_pgrants);
920 if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
921 blkif->vbd.overflow_max_grants = 1;
922 pr_debug("domain %u, device %#x is using maximum number of persistent grants\n",
923 blkif->domid, blkif->vbd.handle);
926 * We could not map this grant persistently, so use it as
927 * a non-persistent grant.
933 last_map = map_until;
934 if (!ret && map_until != num)
938 for (i = last_map; i < num; i++) {
939 /* Don't zap current batch's valid persistent grants. */
941 pages[i]->persistent_gnt = NULL;
942 pages[i]->handle = BLKBACK_INVALID_HANDLE;
948 static int xen_blkbk_map_seg(struct pending_req *pending_req)
952 rc = xen_blkbk_map(pending_req->ring, pending_req->segments,
953 pending_req->nr_segs,
954 (pending_req->operation != BLKIF_OP_READ));
959 static int xen_blkbk_parse_indirect(struct blkif_request *req,
960 struct pending_req *pending_req,
961 struct seg_buf seg[],
962 struct phys_req *preq)
964 struct grant_page **pages = pending_req->indirect_pages;
965 struct xen_blkif_ring *ring = pending_req->ring;
966 int indirect_grefs, rc, n, nseg, i;
967 struct blkif_request_segment *segments = NULL;
969 nseg = pending_req->nr_segs;
970 indirect_grefs = INDIRECT_PAGES(nseg);
971 BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
973 for (i = 0; i < indirect_grefs; i++)
974 pages[i]->gref = req->u.indirect.indirect_grefs[i];
976 rc = xen_blkbk_map(ring, pages, indirect_grefs, true);
980 for (n = 0, i = 0; n < nseg; n++) {
981 uint8_t first_sect, last_sect;
983 if ((n % SEGS_PER_INDIRECT_FRAME) == 0) {
984 /* Map indirect segments */
986 kunmap_atomic(segments);
987 segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page);
989 i = n % SEGS_PER_INDIRECT_FRAME;
991 pending_req->segments[n]->gref = segments[i].gref;
993 first_sect = READ_ONCE(segments[i].first_sect);
994 last_sect = READ_ONCE(segments[i].last_sect);
995 if (last_sect >= (XEN_PAGE_SIZE >> 9) || last_sect < first_sect) {
1000 seg[n].nsec = last_sect - first_sect + 1;
1001 seg[n].offset = first_sect << 9;
1002 preq->nr_sects += seg[n].nsec;
1007 kunmap_atomic(segments);
1008 xen_blkbk_unmap(ring, pages, indirect_grefs);
1012 static int dispatch_discard_io(struct xen_blkif_ring *ring,
1013 struct blkif_request *req)
1016 int status = BLKIF_RSP_OKAY;
1017 struct xen_blkif *blkif = ring->blkif;
1018 struct block_device *bdev = blkif->vbd.bdev;
1019 unsigned long secure;
1020 struct phys_req preq;
1022 xen_blkif_get(blkif);
1024 preq.sector_number = req->u.discard.sector_number;
1025 preq.nr_sects = req->u.discard.nr_sectors;
1027 err = xen_vbd_translate(&preq, blkif, REQ_OP_WRITE);
1029 pr_warn("access denied: DISCARD [%llu->%llu] on dev=%04x\n",
1031 preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
1036 secure = (blkif->vbd.discard_secure &&
1037 (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
1038 BLKDEV_DISCARD_SECURE : 0;
1040 err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
1041 req->u.discard.nr_sectors,
1042 GFP_KERNEL, secure);
1044 if (err == -EOPNOTSUPP) {
1045 pr_debug("discard op failed, not supported\n");
1046 status = BLKIF_RSP_EOPNOTSUPP;
1048 status = BLKIF_RSP_ERROR;
1050 make_response(ring, req->u.discard.id, req->operation, status);
1051 xen_blkif_put(blkif);
1055 static int dispatch_other_io(struct xen_blkif_ring *ring,
1056 struct blkif_request *req,
1057 struct pending_req *pending_req)
1059 free_req(ring, pending_req);
1060 make_response(ring, req->u.other.id, req->operation,
1061 BLKIF_RSP_EOPNOTSUPP);
1065 static void xen_blk_drain_io(struct xen_blkif_ring *ring)
1067 struct xen_blkif *blkif = ring->blkif;
1069 atomic_set(&blkif->drain, 1);
1071 if (atomic_read(&ring->inflight) == 0)
1073 wait_for_completion_interruptible_timeout(
1074 &blkif->drain_complete, HZ);
1076 if (!atomic_read(&blkif->drain))
1078 } while (!kthread_should_stop());
1079 atomic_set(&blkif->drain, 0);
1082 static void __end_block_io_op(struct pending_req *pending_req,
1085 /* An error fails the entire request. */
1086 if (pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE &&
1087 error == BLK_STS_NOTSUPP) {
1088 pr_debug("flush diskcache op failed, not supported\n");
1089 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->ring->blkif->be, 0);
1090 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1091 } else if (pending_req->operation == BLKIF_OP_WRITE_BARRIER &&
1092 error == BLK_STS_NOTSUPP) {
1093 pr_debug("write barrier op failed, not supported\n");
1094 xen_blkbk_barrier(XBT_NIL, pending_req->ring->blkif->be, 0);
1095 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1097 pr_debug("Buffer not up-to-date at end of operation,"
1098 " error=%d\n", error);
1099 pending_req->status = BLKIF_RSP_ERROR;
1103 * If all of the bio's have completed it is time to unmap
1104 * the grant references associated with 'request' and provide
1105 * the proper response on the ring.
1107 if (atomic_dec_and_test(&pending_req->pendcnt))
1108 xen_blkbk_unmap_and_respond(pending_req);
1114 static void end_block_io_op(struct bio *bio)
1116 __end_block_io_op(bio->bi_private, bio->bi_status);
1123 * Function to copy the from the ring buffer the 'struct blkif_request'
1124 * (which has the sectors we want, number of them, grant references, etc),
1125 * and transmute it to the block API to hand it over to the proper block disk.
1128 __do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
1130 union blkif_back_rings *blk_rings = &ring->blk_rings;
1131 struct blkif_request req;
1132 struct pending_req *pending_req;
1136 rc = blk_rings->common.req_cons;
1137 rp = blk_rings->common.sring->req_prod;
1138 rmb(); /* Ensure we see queued requests up to 'rp'. */
1140 if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) {
1141 rc = blk_rings->common.rsp_prod_pvt;
1142 pr_warn("Frontend provided bogus ring requests (%d - %d = %d). Halting ring processing on dev=%04x\n",
1143 rp, rc, rp - rc, ring->blkif->vbd.pdevice);
1148 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
1151 /* We've seen a request, so clear spurious eoi flag. */
1152 *eoi_flags &= ~XEN_EOI_FLAG_SPURIOUS;
1154 if (kthread_should_stop()) {
1159 pending_req = alloc_req(ring);
1160 if (NULL == pending_req) {
1166 switch (ring->blkif->blk_protocol) {
1167 case BLKIF_PROTOCOL_NATIVE:
1168 memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
1170 case BLKIF_PROTOCOL_X86_32:
1171 blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
1173 case BLKIF_PROTOCOL_X86_64:
1174 blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
1179 blk_rings->common.req_cons = ++rc; /* before make_response() */
1181 /* Apply all sanity checks to /private copy/ of request. */
1184 switch (req.operation) {
1186 case BLKIF_OP_WRITE:
1187 case BLKIF_OP_WRITE_BARRIER:
1188 case BLKIF_OP_FLUSH_DISKCACHE:
1189 case BLKIF_OP_INDIRECT:
1190 if (dispatch_rw_block_io(ring, &req, pending_req))
1193 case BLKIF_OP_DISCARD:
1194 free_req(ring, pending_req);
1195 if (dispatch_discard_io(ring, &req))
1199 if (dispatch_other_io(ring, &req, pending_req))
1204 /* Yield point for this unbounded loop. */
1212 do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
1214 union blkif_back_rings *blk_rings = &ring->blk_rings;
1218 more_to_do = __do_block_io_op(ring, eoi_flags);
1222 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
1223 } while (more_to_do);
1228 * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
1229 * and call the 'submit_bio' to pass it to the underlying storage.
1231 static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
1232 struct blkif_request *req,
1233 struct pending_req *pending_req)
1235 struct phys_req preq;
1236 struct seg_buf *seg = pending_req->seg;
1238 struct bio *bio = NULL;
1239 struct bio **biolist = pending_req->biolist;
1242 int operation_flags = 0;
1243 struct blk_plug plug;
1245 struct grant_page **pages = pending_req->segments;
1246 unsigned short req_operation;
1248 req_operation = req->operation == BLKIF_OP_INDIRECT ?
1249 req->u.indirect.indirect_op : req->operation;
1251 if ((req->operation == BLKIF_OP_INDIRECT) &&
1252 (req_operation != BLKIF_OP_READ) &&
1253 (req_operation != BLKIF_OP_WRITE)) {
1254 pr_debug("Invalid indirect operation (%u)\n", req_operation);
1258 switch (req_operation) {
1261 operation = REQ_OP_READ;
1263 case BLKIF_OP_WRITE:
1265 operation = REQ_OP_WRITE;
1266 operation_flags = REQ_SYNC | REQ_IDLE;
1268 case BLKIF_OP_WRITE_BARRIER:
1271 case BLKIF_OP_FLUSH_DISKCACHE:
1273 operation = REQ_OP_WRITE;
1274 operation_flags = REQ_PREFLUSH;
1277 operation = 0; /* make gcc happy */
1282 /* Check that the number of segments is sane. */
1283 nseg = req->operation == BLKIF_OP_INDIRECT ?
1284 req->u.indirect.nr_segments : req->u.rw.nr_segments;
1286 if (unlikely(nseg == 0 && operation_flags != REQ_PREFLUSH) ||
1287 unlikely((req->operation != BLKIF_OP_INDIRECT) &&
1288 (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
1289 unlikely((req->operation == BLKIF_OP_INDIRECT) &&
1290 (nseg > MAX_INDIRECT_SEGMENTS))) {
1291 pr_debug("Bad number of segments in request (%d)\n", nseg);
1292 /* Haven't submitted any bio's yet. */
1298 pending_req->ring = ring;
1299 pending_req->id = req->u.rw.id;
1300 pending_req->operation = req_operation;
1301 pending_req->status = BLKIF_RSP_OKAY;
1302 pending_req->nr_segs = nseg;
1304 if (req->operation != BLKIF_OP_INDIRECT) {
1305 preq.dev = req->u.rw.handle;
1306 preq.sector_number = req->u.rw.sector_number;
1307 for (i = 0; i < nseg; i++) {
1308 pages[i]->gref = req->u.rw.seg[i].gref;
1309 seg[i].nsec = req->u.rw.seg[i].last_sect -
1310 req->u.rw.seg[i].first_sect + 1;
1311 seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
1312 if ((req->u.rw.seg[i].last_sect >= (XEN_PAGE_SIZE >> 9)) ||
1313 (req->u.rw.seg[i].last_sect <
1314 req->u.rw.seg[i].first_sect))
1316 preq.nr_sects += seg[i].nsec;
1319 preq.dev = req->u.indirect.handle;
1320 preq.sector_number = req->u.indirect.sector_number;
1321 if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq))
1325 if (xen_vbd_translate(&preq, ring->blkif, operation) != 0) {
1326 pr_debug("access denied: %s of [%llu,%llu] on dev=%04x\n",
1327 operation == REQ_OP_READ ? "read" : "write",
1329 preq.sector_number + preq.nr_sects,
1330 ring->blkif->vbd.pdevice);
1335 * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
1338 for (i = 0; i < nseg; i++) {
1339 if (((int)preq.sector_number|(int)seg[i].nsec) &
1340 ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
1341 pr_debug("Misaligned I/O request from domain %d\n",
1342 ring->blkif->domid);
1347 /* Wait on all outstanding I/O's and once that has been completed
1351 xen_blk_drain_io(pending_req->ring);
1354 * If we have failed at this point, we need to undo the M2P override,
1355 * set gnttab_set_unmap_op on all of the grant references and perform
1356 * the hypercall to unmap the grants - that is all done in
1359 if (xen_blkbk_map_seg(pending_req))
1363 * This corresponding xen_blkif_put is done in __end_block_io_op, or
1364 * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
1366 xen_blkif_get(ring->blkif);
1367 atomic_inc(&ring->inflight);
1369 for (i = 0; i < nseg; i++) {
1370 while ((bio == NULL) ||
1374 seg[i].offset) == 0)) {
1376 int nr_iovecs = min_t(int, (nseg-i), BIO_MAX_PAGES);
1377 bio = bio_alloc(GFP_KERNEL, nr_iovecs);
1378 if (unlikely(bio == NULL))
1381 biolist[nbio++] = bio;
1382 bio_set_dev(bio, preq.bdev);
1383 bio->bi_private = pending_req;
1384 bio->bi_end_io = end_block_io_op;
1385 bio->bi_iter.bi_sector = preq.sector_number;
1386 bio_set_op_attrs(bio, operation, operation_flags);
1389 preq.sector_number += seg[i].nsec;
1392 /* This will be hit if the operation was a flush or discard. */
1394 BUG_ON(operation_flags != REQ_PREFLUSH);
1396 bio = bio_alloc(GFP_KERNEL, 0);
1397 if (unlikely(bio == NULL))
1400 biolist[nbio++] = bio;
1401 bio_set_dev(bio, preq.bdev);
1402 bio->bi_private = pending_req;
1403 bio->bi_end_io = end_block_io_op;
1404 bio_set_op_attrs(bio, operation, operation_flags);
1407 atomic_set(&pending_req->pendcnt, nbio);
1408 blk_start_plug(&plug);
1410 for (i = 0; i < nbio; i++)
1411 submit_bio(biolist[i]);
1413 /* Let the I/Os go.. */
1414 blk_finish_plug(&plug);
1416 if (operation == REQ_OP_READ)
1417 ring->st_rd_sect += preq.nr_sects;
1418 else if (operation == REQ_OP_WRITE)
1419 ring->st_wr_sect += preq.nr_sects;
1424 xen_blkbk_unmap(ring, pending_req->segments,
1425 pending_req->nr_segs);
1427 /* Haven't submitted any bio's yet. */
1428 make_response(ring, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
1429 free_req(ring, pending_req);
1430 msleep(1); /* back off a bit */
1434 for (i = 0; i < nbio; i++)
1435 bio_put(biolist[i]);
1436 atomic_set(&pending_req->pendcnt, 1);
1437 __end_block_io_op(pending_req, BLK_STS_RESOURCE);
1438 msleep(1); /* back off a bit */
1445 * Put a response on the ring on how the operation fared.
1447 static void make_response(struct xen_blkif_ring *ring, u64 id,
1448 unsigned short op, int st)
1450 struct blkif_response *resp;
1451 unsigned long flags;
1452 union blkif_back_rings *blk_rings;
1455 spin_lock_irqsave(&ring->blk_ring_lock, flags);
1456 blk_rings = &ring->blk_rings;
1457 /* Place on the response ring for the relevant domain. */
1458 switch (ring->blkif->blk_protocol) {
1459 case BLKIF_PROTOCOL_NATIVE:
1460 resp = RING_GET_RESPONSE(&blk_rings->native,
1461 blk_rings->native.rsp_prod_pvt);
1463 case BLKIF_PROTOCOL_X86_32:
1464 resp = RING_GET_RESPONSE(&blk_rings->x86_32,
1465 blk_rings->x86_32.rsp_prod_pvt);
1467 case BLKIF_PROTOCOL_X86_64:
1468 resp = RING_GET_RESPONSE(&blk_rings->x86_64,
1469 blk_rings->x86_64.rsp_prod_pvt);
1476 resp->operation = op;
1479 blk_rings->common.rsp_prod_pvt++;
1480 RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1481 spin_unlock_irqrestore(&ring->blk_ring_lock, flags);
1483 notify_remote_via_irq(ring->irq);
1486 static int __init xen_blkif_init(void)
1493 if (xen_blkif_max_ring_order > XENBUS_MAX_RING_GRANT_ORDER) {
1494 pr_info("Invalid max_ring_order (%d), will use default max: %d.\n",
1495 xen_blkif_max_ring_order, XENBUS_MAX_RING_GRANT_ORDER);
1496 xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;
1499 if (xenblk_max_queues == 0)
1500 xenblk_max_queues = num_online_cpus();
1502 rc = xen_blkif_interface_init();
1506 rc = xen_blkif_xenbus_init();
1514 module_init(xen_blkif_init);
1516 MODULE_LICENSE("Dual BSD/GPL");
1517 MODULE_ALIAS("xen-backend:vbd");