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 /*
  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