xref: /openbmc/qemu/block/export/export.c (revision b86c6ba6) 
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 
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 
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 
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 
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 */
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 
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  */
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  */
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 */
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 
298 void blk_exp_close_all(void)
299 {
300     blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
301 }
302 
303 void qmp_block_export_add(BlockExportOptions *export, Error **errp)
304 {
305     blk_exp_add(export, errp);
306 }
307 
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 
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