xref: /openbmc/qemu/block/write-threshold.c (revision 91bfcdb0) 
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 "qemu/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 }
126