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