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 bdrv_add_before_write_notifier(bs, &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 } 126