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