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