LXR qemu/block/write-threshold.c

   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
  13#include "qemu/osdep.h"
  14#include "block/block_int.h"
  15#include "qemu/coroutine.h"
  16#include "block/write-threshold.h"
  17#include "qemu/notify.h"
  18#include "qapi/error.h"
  19#include "qapi/qapi-commands-block-core.h"
  20#include "qapi/qapi-events-block-core.h"
  21
  22uint64_t bdrv_write_threshold_get(const BlockDriverState *bs)
  23{
  24    return bs->write_threshold_offset;
  25}
  26
  27bool bdrv_write_threshold_is_set(const BlockDriverState *bs)
  28{
  29    return bs->write_threshold_offset > 0;
  30}
  31
  32static void write_threshold_disable(BlockDriverState *bs)
  33{
  34    if (bdrv_write_threshold_is_set(bs)) {
  35        notifier_with_return_remove(&bs->write_threshold_notifier);
  36        bs->write_threshold_offset = 0;
  37    }
  38}
  39
  40uint64_t bdrv_write_threshold_exceeded(const BlockDriverState *bs,
  41                                       const BdrvTrackedRequest *req)
  42{
  43    if (bdrv_write_threshold_is_set(bs)) {
  44        if (req->offset > bs->write_threshold_offset) {
  45            return (req->offset - bs->write_threshold_offset) + req->bytes;
  46        }
  47        if ((req->offset + req->bytes) > bs->write_threshold_offset) {
  48            return (req->offset + req->bytes) - bs->write_threshold_offset;
  49        }
  50    }
  51    return 0;
  52}
  53
  54static int coroutine_fn before_write_notify(NotifierWithReturn *notifier,
  55                                            void *opaque)
  56{
  57    BdrvTrackedRequest *req = opaque;
  58    BlockDriverState *bs = req->bs;
  59    uint64_t amount = 0;
  60
  61    amount = bdrv_write_threshold_exceeded(bs, req);
  62    if (amount > 0) {
  63        qapi_event_send_block_write_threshold(
  64            bs->node_name,
  65            amount,
  66            bs->write_threshold_offset);
  67
  68        /* autodisable to avoid flooding the monitor */
  69        write_threshold_disable(bs);
  70    }
  71
  72    return 0; /* should always let other notifiers run */
  73}
  74
  75static void write_threshold_register_notifier(BlockDriverState *bs)
  76{
  77    bs->write_threshold_notifier.notify = before_write_notify;
  78    bdrv_add_before_write_notifier(bs, &bs->write_threshold_notifier);
  79}
  80
  81static void write_threshold_update(BlockDriverState *bs,
  82                                   int64_t threshold_bytes)
  83{
  84    bs->write_threshold_offset = threshold_bytes;
  85}
  86
  87void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t threshold_bytes)
  88{
  89    if (bdrv_write_threshold_is_set(bs)) {
  90        if (threshold_bytes > 0) {
  91            write_threshold_update(bs, threshold_bytes);
  92        } else {
  93            write_threshold_disable(bs);
  94        }
  95    } else {
  96        if (threshold_bytes > 0) {
  97            /* avoid multiple registration */
  98            write_threshold_register_notifier(bs);
  99            write_threshold_update(bs, threshold_bytes);
 100        }
 101        /* discard bogus disable request */
 102    }
 103}
 104
 105void qmp_block_set_write_threshold(const char *node_name,
 106                                   uint64_t threshold_bytes,
 107                                   Error **errp)
 108{
 109    BlockDriverState *bs;
 110    AioContext *aio_context;
 111
 112    bs = bdrv_find_node(node_name);
 113    if (!bs) {
 114        error_setg(errp, "Device '%s' not found", node_name);
 115        return;
 116    }
 117
 118    aio_context = bdrv_get_aio_context(bs);
 119    aio_context_acquire(aio_context);
 120
 121    bdrv_write_threshold_set(bs, threshold_bytes);
 122
 123    aio_context_release(aio_context);
 124}
 125