1 /*
2 * Common block export infrastructure
3 *
4 * Copyright (c) 2012, 2020 Red Hat, Inc.
5 *
6 * Authors:
7 * Paolo Bonzini <pbonzini@redhat.com>
8 * Kevin Wolf <kwolf@redhat.com>
9 *
10 * This work is licensed under the terms of the GNU GPL, version 2 or
11 * later. See the COPYING file in the top-level directory.
12 */
13
14 #include "qemu/osdep.h"
15
16 #include "block/block.h"
17 #include "sysemu/block-backend.h"
18 #include "sysemu/iothread.h"
19 #include "block/export.h"
20 #include "block/fuse.h"
21 #include "block/nbd.h"
22 #include "qapi/error.h"
23 #include "qapi/qapi-commands-block-export.h"
24 #include "qapi/qapi-events-block-export.h"
25 #include "qemu/id.h"
26 #ifdef CONFIG_VHOST_USER_BLK_SERVER
27 #include "vhost-user-blk-server.h"
28 #endif
29 #ifdef CONFIG_VDUSE_BLK_EXPORT
30 #include "vduse-blk.h"
31 #endif
32
33 static const BlockExportDriver *blk_exp_drivers[] = {
34 &blk_exp_nbd,
35 #ifdef CONFIG_VHOST_USER_BLK_SERVER
36 &blk_exp_vhost_user_blk,
37 #endif
38 #ifdef CONFIG_FUSE
39 &blk_exp_fuse,
40 #endif
41 #ifdef CONFIG_VDUSE_BLK_EXPORT
42 &blk_exp_vduse_blk,
43 #endif
44 };
45
46 /* Only accessed from the main thread */
47 static QLIST_HEAD(, BlockExport) block_exports =
48 QLIST_HEAD_INITIALIZER(block_exports);
49
blk_exp_find(const char * id)50 BlockExport *blk_exp_find(const char *id)
51 {
52 BlockExport *exp;
53
54 QLIST_FOREACH(exp, &block_exports, next) {
55 if (strcmp(id, exp->id) == 0) {
56 return exp;
57 }
58 }
59
60 return NULL;
61 }
62
blk_exp_find_driver(BlockExportType type)63 static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
64 {
65 int i;
66
67 for (i = 0; i < ARRAY_SIZE(blk_exp_drivers); i++) {
68 if (blk_exp_drivers[i]->type == type) {
69 return blk_exp_drivers[i];
70 }
71 }
72 return NULL;
73 }
74
blk_exp_add(BlockExportOptions * export,Error ** errp)75 BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
76 {
77 bool fixed_iothread = export->has_fixed_iothread && export->fixed_iothread;
78 const BlockExportDriver *drv;
79 BlockExport *exp = NULL;
80 BlockDriverState *bs;
81 BlockBackend *blk = NULL;
82 AioContext *ctx;
83 uint64_t perm;
84 int ret;
85
86 GLOBAL_STATE_CODE();
87
88 if (!id_wellformed(export->id)) {
89 error_setg(errp, "Invalid block export id");
90 return NULL;
91 }
92 if (blk_exp_find(export->id)) {
93 error_setg(errp, "Block export id '%s' is already in use", export->id);
94 return NULL;
95 }
96
97 drv = blk_exp_find_driver(export->type);
98 if (!drv) {
99 error_setg(errp, "No driver found for the requested export type");
100 return NULL;
101 }
102
103 bs = bdrv_lookup_bs(NULL, export->node_name, errp);
104 if (!bs) {
105 return NULL;
106 }
107
108 if (!export->has_writable) {
109 export->writable = false;
110 }
111 if (bdrv_is_read_only(bs) && export->writable) {
112 error_setg(errp, "Cannot export read-only node as writable");
113 return NULL;
114 }
115
116 ctx = bdrv_get_aio_context(bs);
117
118 if (export->iothread) {
119 IOThread *iothread;
120 AioContext *new_ctx;
121 Error **set_context_errp;
122
123 iothread = iothread_by_id(export->iothread);
124 if (!iothread) {
125 error_setg(errp, "iothread \"%s\" not found", export->iothread);
126 goto fail;
127 }
128
129 new_ctx = iothread_get_aio_context(iothread);
130
131 /* Ignore errors with fixed-iothread=false */
132 set_context_errp = fixed_iothread ? errp : NULL;
133 ret = bdrv_try_change_aio_context(bs, new_ctx, NULL, set_context_errp);
134 if (ret == 0) {
135 ctx = new_ctx;
136 } else if (fixed_iothread) {
137 goto fail;
138 }
139 }
140
141 /*
142 * Block exports are used for non-shared storage migration. Make sure
143 * that BDRV_O_INACTIVE is cleared and the image is ready for write
144 * access since the export could be available before migration handover.
145 * ctx was acquired in the caller.
146 */
147 bdrv_graph_rdlock_main_loop();
148 bdrv_activate(bs, NULL);
149 bdrv_graph_rdunlock_main_loop();
150
151 perm = BLK_PERM_CONSISTENT_READ;
152 if (export->writable) {
153 perm |= BLK_PERM_WRITE;
154 }
155
156 blk = blk_new(ctx, perm, BLK_PERM_ALL);
157
158 if (!fixed_iothread) {
159 blk_set_allow_aio_context_change(blk, true);
160 }
161
162 ret = blk_insert_bs(blk, bs, errp);
163 if (ret < 0) {
164 goto fail;
165 }
166
167 if (!export->has_writethrough) {
168 export->writethrough = false;
169 }
170 blk_set_enable_write_cache(blk, !export->writethrough);
171
172 assert(drv->instance_size >= sizeof(BlockExport));
173 exp = g_malloc0(drv->instance_size);
174 *exp = (BlockExport) {
175 .drv = drv,
176 .refcount = 1,
177 .user_owned = true,
178 .id = g_strdup(export->id),
179 .ctx = ctx,
180 .blk = blk,
181 };
182
183 ret = drv->create(exp, export, errp);
184 if (ret < 0) {
185 goto fail;
186 }
187
188 assert(exp->blk != NULL);
189
190 QLIST_INSERT_HEAD(&block_exports, exp, next);
191 return exp;
192
193 fail:
194 if (blk) {
195 blk_set_dev_ops(blk, NULL, NULL);
196 blk_unref(blk);
197 }
198 if (exp) {
199 g_free(exp->id);
200 g_free(exp);
201 }
202 return NULL;
203 }
204
blk_exp_ref(BlockExport * exp)205 void blk_exp_ref(BlockExport *exp)
206 {
207 assert(qatomic_read(&exp->refcount) > 0);
208 qatomic_inc(&exp->refcount);
209 }
210
211 /* Runs in the main thread */
blk_exp_delete_bh(void * opaque)212 static void blk_exp_delete_bh(void *opaque)
213 {
214 BlockExport *exp = opaque;
215
216 assert(exp->refcount == 0);
217 QLIST_REMOVE(exp, next);
218 exp->drv->delete(exp);
219 blk_set_dev_ops(exp->blk, NULL, NULL);
220 blk_unref(exp->blk);
221 qapi_event_send_block_export_deleted(exp->id);
222 g_free(exp->id);
223 g_free(exp);
224 }
225
blk_exp_unref(BlockExport * exp)226 void blk_exp_unref(BlockExport *exp)
227 {
228 assert(qatomic_read(&exp->refcount) > 0);
229 if (qatomic_fetch_dec(&exp->refcount) == 1) {
230 /* Touch the block_exports list only in the main thread */
231 aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh,
232 exp);
233 }
234 }
235
236 /*
237 * Drops the user reference to the export and requests that all client
238 * connections and other internally held references start to shut down. When
239 * the function returns, there may still be active references while the export
240 * is in the process of shutting down.
241 */
blk_exp_request_shutdown(BlockExport * exp)242 void blk_exp_request_shutdown(BlockExport *exp)
243 {
244 /*
245 * If the user doesn't own the export any more, it is already shutting
246 * down. We must not call .request_shutdown and decrease the refcount a
247 * second time.
248 */
249 if (!exp->user_owned) {
250 return;
251 }
252
253 exp->drv->request_shutdown(exp);
254
255 assert(exp->user_owned);
256 exp->user_owned = false;
257 blk_exp_unref(exp);
258 }
259
260 /*
261 * Returns whether a block export of the given type exists.
262 * type == BLOCK_EXPORT_TYPE__MAX checks for an export of any type.
263 */
blk_exp_has_type(BlockExportType type)264 static bool blk_exp_has_type(BlockExportType type)
265 {
266 BlockExport *exp;
267
268 if (type == BLOCK_EXPORT_TYPE__MAX) {
269 return !QLIST_EMPTY(&block_exports);
270 }
271
272 QLIST_FOREACH(exp, &block_exports, next) {
273 if (exp->drv->type == type) {
274 return true;
275 }
276 }
277
278 return false;
279 }
280
281 /* type == BLOCK_EXPORT_TYPE__MAX for all types */
blk_exp_close_all_type(BlockExportType type)282 void blk_exp_close_all_type(BlockExportType type)
283 {
284 BlockExport *exp, *next;
285
286 assert(in_aio_context_home_thread(qemu_get_aio_context()));
287
288 QLIST_FOREACH_SAFE(exp, &block_exports, next, next) {
289 if (type != BLOCK_EXPORT_TYPE__MAX && exp->drv->type != type) {
290 continue;
291 }
292 blk_exp_request_shutdown(exp);
293 }
294
295 AIO_WAIT_WHILE_UNLOCKED(NULL, blk_exp_has_type(type));
296 }
297
blk_exp_close_all(void)298 void blk_exp_close_all(void)
299 {
300 blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
301 }
302
qmp_block_export_add(BlockExportOptions * export,Error ** errp)303 void qmp_block_export_add(BlockExportOptions *export, Error **errp)
304 {
305 blk_exp_add(export, errp);
306 }
307
qmp_block_export_del(const char * id,bool has_mode,BlockExportRemoveMode mode,Error ** errp)308 void qmp_block_export_del(const char *id,
309 bool has_mode, BlockExportRemoveMode mode,
310 Error **errp)
311 {
312 ERRP_GUARD();
313 BlockExport *exp;
314
315 exp = blk_exp_find(id);
316 if (exp == NULL) {
317 error_setg(errp, "Export '%s' is not found", id);
318 return;
319 }
320 if (!exp->user_owned) {
321 error_setg(errp, "Export '%s' is already shutting down", id);
322 return;
323 }
324
325 if (!has_mode) {
326 mode = BLOCK_EXPORT_REMOVE_MODE_SAFE;
327 }
328 if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE &&
329 qatomic_read(&exp->refcount) > 1) {
330 error_setg(errp, "export '%s' still in use", exp->id);
331 error_append_hint(errp, "Use mode='hard' to force client "
332 "disconnect\n");
333 return;
334 }
335
336 blk_exp_request_shutdown(exp);
337 }
338
qmp_query_block_exports(Error ** errp)339 BlockExportInfoList *qmp_query_block_exports(Error **errp)
340 {
341 BlockExportInfoList *head = NULL, **tail = &head;
342 BlockExport *exp;
343
344 QLIST_FOREACH(exp, &block_exports, next) {
345 BlockExportInfo *info = g_new(BlockExportInfo, 1);
346 *info = (BlockExportInfo) {
347 .id = g_strdup(exp->id),
348 .type = exp->drv->type,
349 .node_name = g_strdup(bdrv_get_node_name(blk_bs(exp->blk))),
350 .shutting_down = !exp->user_owned,
351 };
352
353 QAPI_LIST_APPEND(tail, info);
354 }
355
356 return head;
357 }
358