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 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 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 bdrv_add_before_write_notifier(bs, &bs->write_threshold_notifier); 79 } 80 81 static void write_threshold_update(BlockDriverState *bs, 82 int64_t threshold_bytes) 83 { 84 bs->write_threshold_offset = threshold_bytes; 85 } 86 87 void 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 } 104 105 void 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