block: move logical block size check function to a common utility function
[qemu.git] / block / stream.c
blob8ce6729a33da478a2454ed285d79241ad10ec006
1 /*
2 * Image streaming
4 * Copyright IBM, Corp. 2011
6 * Authors:
7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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.
14 #include "qemu/osdep.h"
15 #include "trace.h"
16 #include "block/block_int.h"
17 #include "block/blockjob_int.h"
18 #include "qapi/error.h"
19 #include "qapi/qmp/qerror.h"
20 #include "qemu/ratelimit.h"
21 #include "sysemu/block-backend.h"
23 enum {
25 * Maximum chunk size to feed to copy-on-read. This should be
26 * large enough to process multiple clusters in a single call, so
27 * that populating contiguous regions of the image is efficient.
29 STREAM_CHUNK = 512 * 1024, /* in bytes */
32 typedef struct StreamBlockJob {
33 BlockJob common;
34 BlockDriverState *base_overlay; /* COW overlay (stream from this) */
35 BlockDriverState *above_base; /* Node directly above the base */
36 BlockdevOnError on_error;
37 char *backing_file_str;
38 bool bs_read_only;
39 bool chain_frozen;
40 } StreamBlockJob;
42 static int coroutine_fn stream_populate(BlockBackend *blk,
43 int64_t offset, uint64_t bytes)
45 assert(bytes < SIZE_MAX);
47 return blk_co_preadv(blk, offset, bytes, NULL,
48 BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
51 static void stream_abort(Job *job)
53 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
55 if (s->chain_frozen) {
56 BlockJob *bjob = &s->common;
57 bdrv_unfreeze_backing_chain(blk_bs(bjob->blk), s->above_base);
61 static int stream_prepare(Job *job)
63 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
64 BlockJob *bjob = &s->common;
65 BlockDriverState *bs = blk_bs(bjob->blk);
66 BlockDriverState *unfiltered_bs = bdrv_skip_filters(bs);
67 BlockDriverState *base = bdrv_filter_or_cow_bs(s->above_base);
68 Error *local_err = NULL;
69 int ret = 0;
71 bdrv_unfreeze_backing_chain(bs, s->above_base);
72 s->chain_frozen = false;
74 if (bdrv_cow_child(unfiltered_bs)) {
75 const char *base_id = NULL, *base_fmt = NULL;
76 if (base) {
77 base_id = s->backing_file_str;
78 if (base->drv) {
79 base_fmt = base->drv->format_name;
82 bdrv_set_backing_hd(unfiltered_bs, base, &local_err);
83 ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false);
84 if (local_err) {
85 error_report_err(local_err);
86 return -EPERM;
90 return ret;
93 static void stream_clean(Job *job)
95 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
96 BlockJob *bjob = &s->common;
97 BlockDriverState *bs = blk_bs(bjob->blk);
99 /* Reopen the image back in read-only mode if necessary */
100 if (s->bs_read_only) {
101 /* Give up write permissions before making it read-only */
102 blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
103 bdrv_reopen_set_read_only(bs, true, NULL);
106 g_free(s->backing_file_str);
109 static int coroutine_fn stream_run(Job *job, Error **errp)
111 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
112 BlockBackend *blk = s->common.blk;
113 BlockDriverState *bs = blk_bs(blk);
114 BlockDriverState *unfiltered_bs = bdrv_skip_filters(bs);
115 bool enable_cor = !bdrv_cow_child(s->base_overlay);
116 int64_t len;
117 int64_t offset = 0;
118 uint64_t delay_ns = 0;
119 int error = 0;
120 int64_t n = 0; /* bytes */
122 if (unfiltered_bs == s->base_overlay) {
123 /* Nothing to stream */
124 return 0;
127 len = bdrv_getlength(bs);
128 if (len < 0) {
129 return len;
131 job_progress_set_remaining(&s->common.job, len);
133 /* Turn on copy-on-read for the whole block device so that guest read
134 * requests help us make progress. Only do this when copying the entire
135 * backing chain since the copy-on-read operation does not take base into
136 * account.
138 if (enable_cor) {
139 bdrv_enable_copy_on_read(bs);
142 for ( ; offset < len; offset += n) {
143 bool copy;
144 int ret;
146 /* Note that even when no rate limit is applied we need to yield
147 * with no pending I/O here so that bdrv_drain_all() returns.
149 job_sleep_ns(&s->common.job, delay_ns);
150 if (job_is_cancelled(&s->common.job)) {
151 break;
154 copy = false;
156 ret = bdrv_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &n);
157 if (ret == 1) {
158 /* Allocated in the top, no need to copy. */
159 } else if (ret >= 0) {
160 /* Copy if allocated in the intermediate images. Limit to the
161 * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE). */
162 ret = bdrv_is_allocated_above(bdrv_cow_bs(unfiltered_bs),
163 s->base_overlay, true,
164 offset, n, &n);
165 /* Finish early if end of backing file has been reached */
166 if (ret == 0 && n == 0) {
167 n = len - offset;
170 copy = (ret == 1);
172 trace_stream_one_iteration(s, offset, n, ret);
173 if (copy) {
174 ret = stream_populate(blk, offset, n);
176 if (ret < 0) {
177 BlockErrorAction action =
178 block_job_error_action(&s->common, s->on_error, true, -ret);
179 if (action == BLOCK_ERROR_ACTION_STOP) {
180 n = 0;
181 continue;
183 if (error == 0) {
184 error = ret;
186 if (action == BLOCK_ERROR_ACTION_REPORT) {
187 break;
191 /* Publish progress */
192 job_progress_update(&s->common.job, n);
193 if (copy) {
194 delay_ns = block_job_ratelimit_get_delay(&s->common, n);
195 } else {
196 delay_ns = 0;
200 if (enable_cor) {
201 bdrv_disable_copy_on_read(bs);
204 /* Do not remove the backing file if an error was there but ignored. */
205 return error;
208 static const BlockJobDriver stream_job_driver = {
209 .job_driver = {
210 .instance_size = sizeof(StreamBlockJob),
211 .job_type = JOB_TYPE_STREAM,
212 .free = block_job_free,
213 .run = stream_run,
214 .prepare = stream_prepare,
215 .abort = stream_abort,
216 .clean = stream_clean,
217 .user_resume = block_job_user_resume,
221 void stream_start(const char *job_id, BlockDriverState *bs,
222 BlockDriverState *base, const char *backing_file_str,
223 int creation_flags, int64_t speed,
224 BlockdevOnError on_error, Error **errp)
226 StreamBlockJob *s;
227 BlockDriverState *iter;
228 bool bs_read_only;
229 int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
230 BlockDriverState *base_overlay = bdrv_find_overlay(bs, base);
231 BlockDriverState *above_base;
233 if (!base_overlay) {
234 error_setg(errp, "'%s' is not in the backing chain of '%s'",
235 base->node_name, bs->node_name);
236 return;
240 * Find the node directly above @base. @base_overlay is a COW overlay, so
241 * it must have a bdrv_cow_child(), but it is the immediate overlay of
242 * @base, so between the two there can only be filters.
244 above_base = base_overlay;
245 if (bdrv_cow_bs(above_base) != base) {
246 above_base = bdrv_cow_bs(above_base);
247 while (bdrv_filter_bs(above_base) != base) {
248 above_base = bdrv_filter_bs(above_base);
252 if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
253 return;
256 /* Make sure that the image is opened in read-write mode */
257 bs_read_only = bdrv_is_read_only(bs);
258 if (bs_read_only) {
259 if (bdrv_reopen_set_read_only(bs, false, errp) != 0) {
260 bs_read_only = false;
261 goto fail;
265 /* Prevent concurrent jobs trying to modify the graph structure here, we
266 * already have our own plans. Also don't allow resize as the image size is
267 * queried only at the job start and then cached. */
268 s = block_job_create(job_id, &stream_job_driver, NULL, bs,
269 basic_flags | BLK_PERM_GRAPH_MOD,
270 basic_flags | BLK_PERM_WRITE,
271 speed, creation_flags, NULL, NULL, errp);
272 if (!s) {
273 goto fail;
276 /* Block all intermediate nodes between bs and base, because they will
277 * disappear from the chain after this operation. The streaming job reads
278 * every block only once, assuming that it doesn't change, so forbid writes
279 * and resizes. Reassign the base node pointer because the backing BS of the
280 * bottom node might change after the call to bdrv_reopen_set_read_only()
281 * due to parallel block jobs running.
282 * above_base node might change after the call to
283 * bdrv_reopen_set_read_only() due to parallel block jobs running.
285 base = bdrv_filter_or_cow_bs(above_base);
286 for (iter = bdrv_filter_or_cow_bs(bs); iter != base;
287 iter = bdrv_filter_or_cow_bs(iter))
289 block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
290 basic_flags, &error_abort);
293 s->base_overlay = base_overlay;
294 s->above_base = above_base;
295 s->backing_file_str = g_strdup(backing_file_str);
296 s->bs_read_only = bs_read_only;
297 s->chain_frozen = true;
299 s->on_error = on_error;
300 trace_stream_start(bs, base, s);
301 job_start(&s->common.job);
302 return;
304 fail:
305 if (bs_read_only) {
306 bdrv_reopen_set_read_only(bs, true, NULL);
308 bdrv_unfreeze_backing_chain(bs, above_base);