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