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 "qemu/osdep.h" |
14 | #include "block/block_int.h" |
15 | #include "qemu/coroutine.h" |
16 | #include "block/write-threshold.h" |
17 | #include "qemu/notify.h" |
18 | #include "qapi/error.h" |
19 | #include "qapi/qapi-commands-block-core.h" |
20 | #include "qapi/qapi-events-block-core.h" |
21 | |
22 | uint64_t bdrv_write_threshold_get(const BlockDriverState *bs) |
23 | { |
24 | return bs->write_threshold_offset; |
25 | } |
26 | |
27 | bool bdrv_write_threshold_is_set(const BlockDriverState *bs) |
28 | { |
29 | return bs->write_threshold_offset > 0; |
30 | } |
31 | |
32 | static void write_threshold_disable(BlockDriverState *bs) |
33 | { |
34 | if (bdrv_write_threshold_is_set(bs)) { |
35 | notifier_with_return_remove(&bs->write_threshold_notifier); |
36 | bs->write_threshold_offset = 0; |
37 | } |
38 | } |
39 | |
40 | uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs, |
41 | const BdrvTrackedRequest *req) |
42 | { |
43 | if (bdrv_write_threshold_is_set(bs)) { |
44 | if (req->offset > bs->write_threshold_offset) { |
45 | return (req->offset - bs->write_threshold_offset) + req->bytes; |
46 | } |
47 | if ((req->offset + req->bytes) > bs->write_threshold_offset) { |
48 | return (req->offset + req->bytes) - bs->write_threshold_offset; |
49 | } |
50 | } |
51 | return 0; |
52 | } |
53 | |
54 | static int coroutine_fn before_write_notify(NotifierWithReturn *notifier, |
55 | void *opaque) |
56 | { |
57 | BdrvTrackedRequest *req = opaque; |
58 | BlockDriverState *bs = req->bs; |
59 | uint64_t amount = 0; |
60 | |
61 | amount = bdrv_write_threshold_exceeded(bs, req); |
62 | if (amount > 0) { |
63 | qapi_event_send_block_write_threshold( |
64 | bs->node_name, |
65 | amount, |
66 | bs->write_threshold_offset); |
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 | bdrv_add_before_write_notifier(bs, &bs->write_threshold_notifier); |
79 | } |
80 | |
81 | static void write_threshold_update(BlockDriverState *bs, |
82 | int64_t threshold_bytes) |
83 | { |
84 | bs->write_threshold_offset = threshold_bytes; |
85 | } |
86 | |
87 | void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t threshold_bytes) |
88 | { |
89 | if (bdrv_write_threshold_is_set(bs)) { |
90 | if (threshold_bytes > 0) { |
91 | write_threshold_update(bs, threshold_bytes); |
92 | } else { |
93 | write_threshold_disable(bs); |
94 | } |
95 | } else { |
96 | if (threshold_bytes > 0) { |
97 | /* avoid multiple registration */ |
98 | write_threshold_register_notifier(bs); |
99 | write_threshold_update(bs, threshold_bytes); |
100 | } |
101 | /* discard bogus disable request */ |
102 | } |
103 | } |
104 | |
105 | void qmp_block_set_write_threshold(const char *node_name, |
106 | uint64_t threshold_bytes, |
107 | Error **errp) |
108 | { |
109 | BlockDriverState *bs; |
110 | AioContext *aio_context; |
111 | |
112 | bs = bdrv_find_node(node_name); |
113 | if (!bs) { |
114 | error_setg(errp, "Device '%s' not found" , node_name); |
115 | return; |
116 | } |
117 | |
118 | aio_context = bdrv_get_aio_context(bs); |
119 | aio_context_acquire(aio_context); |
120 | |
121 | bdrv_write_threshold_set(bs, threshold_bytes); |
122 | |
123 | aio_context_release(aio_context); |
124 | } |
125 | |