include/block/write-threshold.h

   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