134 lines
3.5 KiB
C
134 lines
3.5 KiB
C
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/*
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* Image streaming
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#include "trace.h"
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#include "block_int.h"
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enum {
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/*
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* Size of data buffer for populating the image file. This should be large
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* enough to process multiple clusters in a single call, so that populating
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* contiguous regions of the image is efficient.
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*/
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STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
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};
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typedef struct StreamBlockJob {
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BlockJob common;
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BlockDriverState *base;
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} StreamBlockJob;
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static int coroutine_fn stream_populate(BlockDriverState *bs,
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int64_t sector_num, int nb_sectors,
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void *buf)
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{
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struct iovec iov = {
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.iov_base = buf,
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.iov_len = nb_sectors * BDRV_SECTOR_SIZE,
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};
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QEMUIOVector qiov;
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qemu_iovec_init_external(&qiov, &iov, 1);
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/* Copy-on-read the unallocated clusters */
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return bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, &qiov);
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}
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static void coroutine_fn stream_run(void *opaque)
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{
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StreamBlockJob *s = opaque;
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BlockDriverState *bs = s->common.bs;
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int64_t sector_num, end;
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int ret = 0;
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int n;
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void *buf;
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s->common.len = bdrv_getlength(bs);
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if (s->common.len < 0) {
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block_job_complete(&s->common, s->common.len);
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return;
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}
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end = s->common.len >> BDRV_SECTOR_BITS;
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buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
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/* Turn on copy-on-read for the whole block device so that guest read
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* requests help us make progress. Only do this when copying the entire
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* backing chain since the copy-on-read operation does not take base into
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* account.
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*/
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if (!base) {
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bdrv_enable_copy_on_read(bs);
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}
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for (sector_num = 0; sector_num < end; sector_num += n) {
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if (block_job_is_cancelled(&s->common)) {
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break;
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}
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/* TODO rate-limit */
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/* Note that even when no rate limit is applied we need to yield with
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* no pending I/O here so that qemu_aio_flush() is able to return.
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*/
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co_sleep_ns(rt_clock, 0);
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ret = bdrv_co_is_allocated(bs, sector_num,
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STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
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trace_stream_one_iteration(s, sector_num, n, ret);
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if (ret == 0) {
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ret = stream_populate(bs, sector_num, n, buf);
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}
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if (ret < 0) {
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break;
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}
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/* Publish progress */
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s->common.offset += n * BDRV_SECTOR_SIZE;
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}
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if (!base) {
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bdrv_disable_copy_on_read(bs);
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}
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if (sector_num == end && ret == 0) {
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ret = bdrv_change_backing_file(bs, NULL, NULL);
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}
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qemu_vfree(buf);
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block_job_complete(&s->common, ret);
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}
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static BlockJobType stream_job_type = {
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.instance_size = sizeof(StreamBlockJob),
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.job_type = "stream",
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};
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int stream_start(BlockDriverState *bs, BlockDriverState *base,
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BlockDriverCompletionFunc *cb, void *opaque)
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{
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StreamBlockJob *s;
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Coroutine *co;
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s = block_job_create(&stream_job_type, bs, cb, opaque);
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if (!s) {
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return -EBUSY; /* bs must already be in use */
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}
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s->base = base;
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co = qemu_coroutine_create(stream_run);
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trace_stream_start(bs, base, s, co, opaque);
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qemu_coroutine_enter(co, s);
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return 0;
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}
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