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1 /*
2 * QEMU System Emulator block write threshold notification
3 *
4 * Copyright Red Hat, Inc. 2014
5 *
6 * Authors:
7 * Francesco Romani <fromani@redhat.com>
8 *
9 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
10 * See the COPYING.LIB file in the top-level directory.
11 */
12
13 #include "block/block_int.h"
14 #include "block/coroutine.h"
15 #include "block/write-threshold.h"
16 #include "qemu/notify.h"
17 #include "qapi-event.h"
18 #include "qmp-commands.h"
19
20
21 uint64_t bdrv_write_threshold_get(const BlockDriverState *bs)
22 {
23 return bs->write_threshold_offset;
24 }
25
26 bool bdrv_write_threshold_is_set(const BlockDriverState *bs)
27 {
28 return bs->write_threshold_offset > 0;
29 }
30
31 static void write_threshold_disable(BlockDriverState *bs)
32 {
33 if (bdrv_write_threshold_is_set(bs)) {
34 notifier_with_return_remove(&bs->write_threshold_notifier);
35 bs->write_threshold_offset = 0;
36 }
37 }
38
39 uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs,
40 const BdrvTrackedRequest *req)
41 {
42 if (bdrv_write_threshold_is_set(bs)) {
43 if (req->offset > bs->write_threshold_offset) {
44 return (req->offset - bs->write_threshold_offset) + req->bytes;
45 }
46 if ((req->offset + req->bytes) > bs->write_threshold_offset) {
47 return (req->offset + req->bytes) - bs->write_threshold_offset;
48 }
49 }
50 return 0;
51 }
52
53 static int coroutine_fn before_write_notify(NotifierWithReturn *notifier,
54 void *opaque)
55 {
56 BdrvTrackedRequest *req = opaque;
57 BlockDriverState *bs = req->bs;
58 uint64_t amount = 0;
59
60 amount = bdrv_write_threshold_exceeded(bs, req);
61 if (amount > 0) {
62 qapi_event_send_block_write_threshold(
63 bs->node_name,
64 amount,
65 bs->write_threshold_offset,
66 &error_abort);
67
68 /* autodisable to avoid flooding the monitor */
69 write_threshold_disable(bs);
70 }
71
72 return 0; /* should always let other notifiers run */
73 }
74
75 static void write_threshold_register_notifier(BlockDriverState *bs)
76 {
77 bs->write_threshold_notifier.notify = before_write_notify;
78 notifier_with_return_list_add(&bs->before_write_notifiers,
79 &bs->write_threshold_notifier);
80 }
81
82 static void write_threshold_update(BlockDriverState *bs,
83 int64_t threshold_bytes)
84 {
85 bs->write_threshold_offset = threshold_bytes;
86 }
87
88 void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t threshold_bytes)
89 {
90 if (bdrv_write_threshold_is_set(bs)) {
91 if (threshold_bytes > 0) {
92 write_threshold_update(bs, threshold_bytes);
93 } else {
94 write_threshold_disable(bs);
95 }
96 } else {
97 if (threshold_bytes > 0) {
98 /* avoid multiple registration */
99 write_threshold_register_notifier(bs);
100 write_threshold_update(bs, threshold_bytes);
101 }
102 /* discard bogus disable request */
103 }
104 }
105
106 void qmp_block_set_write_threshold(const char *node_name,
107 uint64_t threshold_bytes,
108 Error **errp)
109 {
110 BlockDriverState *bs;
111 AioContext *aio_context;
112
113 bs = bdrv_find_node(node_name);
114 if (!bs) {
115 error_setg(errp, "Device '%s' not found", node_name);
116 return;
117 }
118
119 aio_context = bdrv_get_aio_context(bs);
120 aio_context_acquire(aio_context);
121
122 bdrv_write_threshold_set(bs, threshold_bytes);
123
124 aio_context_release(aio_context);
125 }