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-event.h"
  19 #include "qmp-commands.h"
  20
  21
  22 uint64_t bdrv_write_threshold_get(const BlockDriverState *bs)
  23 {
  24     return bs->write_threshold_offset;
  25 }
  26
  27 bool bdrv_write_threshold_is_set(const BlockDriverState *bs)
  28 {
  29     return bs->write_threshold_offset > 0;
  30 }
  31
  32 static 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
  40 uint64_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
  54 static 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             &error_abort);
  68
  69         /* autodisable to avoid flooding the monitor */
  70         write_threshold_disable(bs);
  71     }
  72
  73     return 0; /* should always let other notifiers run */
  74 }
  75
  76 static void write_threshold_register_notifier(BlockDriverState *bs)
  77 {
  78     bs->write_threshold_notifier.notify = before_write_notify;
  79     notifier_with_return_list_add(&bs->before_write_notifiers,
  80                                   &bs->write_threshold_notifier);
  81 }
  82
  83 static void write_threshold_update(BlockDriverState *bs,
  84                                    int64_t threshold_bytes)
  85 {
  86     bs->write_threshold_offset = threshold_bytes;
  87 }
  88
  89 void bdrv_write_threshold_set(BlockDriverState *bs, uint64_t threshold_bytes)
  90 {
  91     if (bdrv_write_threshold_is_set(bs)) {
  92         if (threshold_bytes > 0) {
  93             write_threshold_update(bs, threshold_bytes);
  94         } else {
  95             write_threshold_disable(bs);
  96         }
  97     } else {
  98         if (threshold_bytes > 0) {
  99             /* avoid multiple registration */
 100             write_threshold_register_notifier(bs);
 101             write_threshold_update(bs, threshold_bytes);
 102         }
 103         /* discard bogus disable request */
 104     }
 105 }
 106
 107 void qmp_block_set_write_threshold(const char *node_name,
 108                                    uint64_t threshold_bytes,
 109                                    Error **errp)
 110 {
 111     BlockDriverState *bs;
 112     AioContext *aio_context;
 113
 114     bs = bdrv_find_node(node_name);
 115     if (!bs) {
 116         error_setg(errp, "Device '%s' not found", node_name);
 117         return;
 118     }
 119
 120     aio_context = bdrv_get_aio_context(bs);
 121     aio_context_acquire(aio_context);
 122
 123     bdrv_write_threshold_set(bs, threshold_bytes);
 124
 125     aio_context_release(aio_context);
 126 }