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 #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