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 #ifndef BLOCK_WRITE_THRESHOLD_H
13 #define BLOCK_WRITE_THRESHOLD_H
14 
15 
16 #include "qemu/typedefs.h"
17 #include "qemu-common.h"
18 
19 /*
20  * bdrv_write_threshold_set:
21  *
22  * Set the write threshold for block devices, in bytes.
23  * Notify when a write exceeds the threshold, meaning the device
24  * is becoming full, so it can be transparently resized.
25  * To be used with thin-provisioned block devices.
26  *
27  * Use threshold_bytes == 0 to disable.
28  */
29 void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t threshold_bytes);
30 
31 /*
32  * bdrv_write_threshold_get
33  *
34  * Get the configured write threshold, in bytes.
35  * Zero means no threshold configured.
36  */
37 uint64_t bdrv_write_threshold_get(const BlockDriverState *bs);
38 
39 /*
40  * bdrv_write_threshold_is_set
41  *
42  * Tell if a write threshold is set for a given BDS.
43  */
44 bool bdrv_write_threshold_is_set(const BlockDriverState *bs);
45 
46 /*
47  * bdrv_write_threshold_exceeded
48  *
49  * Return the extent of a write request that exceeded the threshold,
50  * or zero if the request is below the threshold.
51  * Return zero also if the threshold was not set.
52  *
53  * NOTE: here we assume the following holds for each request this code
54  * deals with:
55  *
56  * assert((req->offset + req->bytes) <= UINT64_MAX)
57  *
58  * Please not there is *not* an actual C assert().
59  */
60 uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs,
61                                        const BdrvTrackedRequest *req);
62 
63 #endif
64