xref: /openbmc/qemu/block/commit.c (revision 8f1e884b)
1 /*
2  * Live block commit
3  *
4  * Copyright Red Hat, Inc. 2012
5  *
6  * Authors:
7  *  Jeff Cody   <jcody@redhat.com>
8  *  Based on stream.c by Stefan Hajnoczi
9  *
10  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
11  * See the COPYING.LIB file in the top-level directory.
12  *
13  */
14 
15 #include "trace.h"
16 #include "block/block_int.h"
17 #include "block/blockjob.h"
18 #include "qemu/ratelimit.h"
19 
20 enum {
21     /*
22      * Size of data buffer for populating the image file.  This should be large
23      * enough to process multiple clusters in a single call, so that populating
24      * contiguous regions of the image is efficient.
25      */
26     COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */
27 };
28 
29 #define SLICE_TIME 100000000ULL /* ns */
30 
31 typedef struct CommitBlockJob {
32     BlockJob common;
33     RateLimit limit;
34     BlockDriverState *active;
35     BlockDriverState *top;
36     BlockDriverState *base;
37     BlockdevOnError on_error;
38     int base_flags;
39     int orig_overlay_flags;
40 } CommitBlockJob;
41 
42 static int coroutine_fn commit_populate(BlockDriverState *bs,
43                                         BlockDriverState *base,
44                                         int64_t sector_num, int nb_sectors,
45                                         void *buf)
46 {
47     int ret = 0;
48 
49     ret = bdrv_read(bs, sector_num, buf, nb_sectors);
50     if (ret) {
51         return ret;
52     }
53 
54     ret = bdrv_write(base, sector_num, buf, nb_sectors);
55     if (ret) {
56         return ret;
57     }
58 
59     return 0;
60 }
61 
62 static void coroutine_fn commit_run(void *opaque)
63 {
64     CommitBlockJob *s = opaque;
65     BlockDriverState *active = s->active;
66     BlockDriverState *top = s->top;
67     BlockDriverState *base = s->base;
68     BlockDriverState *overlay_bs;
69     int64_t sector_num, end;
70     int ret = 0;
71     int n = 0;
72     void *buf;
73     int bytes_written = 0;
74     int64_t base_len;
75 
76     ret = s->common.len = bdrv_getlength(top);
77 
78 
79     if (s->common.len < 0) {
80         goto exit_restore_reopen;
81     }
82 
83     ret = base_len = bdrv_getlength(base);
84     if (base_len < 0) {
85         goto exit_restore_reopen;
86     }
87 
88     if (base_len < s->common.len) {
89         ret = bdrv_truncate(base, s->common.len);
90         if (ret) {
91             goto exit_restore_reopen;
92         }
93     }
94 
95     end = s->common.len >> BDRV_SECTOR_BITS;
96     buf = qemu_blockalign(top, COMMIT_BUFFER_SIZE);
97 
98     for (sector_num = 0; sector_num < end; sector_num += n) {
99         uint64_t delay_ns = 0;
100         bool copy;
101 
102 wait:
103         /* Note that even when no rate limit is applied we need to yield
104          * with no pending I/O here so that bdrv_drain_all() returns.
105          */
106         block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
107         if (block_job_is_cancelled(&s->common)) {
108             break;
109         }
110         /* Copy if allocated above the base */
111         ret = bdrv_is_allocated_above(top, base, sector_num,
112                                       COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,
113                                       &n);
114         copy = (ret == 1);
115         trace_commit_one_iteration(s, sector_num, n, ret);
116         if (copy) {
117             if (s->common.speed) {
118                 delay_ns = ratelimit_calculate_delay(&s->limit, n);
119                 if (delay_ns > 0) {
120                     goto wait;
121                 }
122             }
123             ret = commit_populate(top, base, sector_num, n, buf);
124             bytes_written += n * BDRV_SECTOR_SIZE;
125         }
126         if (ret < 0) {
127             if (s->on_error == BLOCKDEV_ON_ERROR_STOP ||
128                 s->on_error == BLOCKDEV_ON_ERROR_REPORT||
129                 (s->on_error == BLOCKDEV_ON_ERROR_ENOSPC && ret == -ENOSPC)) {
130                 goto exit_free_buf;
131             } else {
132                 n = 0;
133                 continue;
134             }
135         }
136         /* Publish progress */
137         s->common.offset += n * BDRV_SECTOR_SIZE;
138     }
139 
140     ret = 0;
141 
142     if (!block_job_is_cancelled(&s->common) && sector_num == end) {
143         /* success */
144         ret = bdrv_drop_intermediate(active, top, base);
145     }
146 
147 exit_free_buf:
148     qemu_vfree(buf);
149 
150 exit_restore_reopen:
151     /* restore base open flags here if appropriate (e.g., change the base back
152      * to r/o). These reopens do not need to be atomic, since we won't abort
153      * even on failure here */
154     if (s->base_flags != bdrv_get_flags(base)) {
155         bdrv_reopen(base, s->base_flags, NULL);
156     }
157     overlay_bs = bdrv_find_overlay(active, top);
158     if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
159         bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);
160     }
161 
162     block_job_completed(&s->common, ret);
163 }
164 
165 static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp)
166 {
167     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
168 
169     if (speed < 0) {
170         error_set(errp, QERR_INVALID_PARAMETER, "speed");
171         return;
172     }
173     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
174 }
175 
176 static const BlockJobDriver commit_job_driver = {
177     .instance_size = sizeof(CommitBlockJob),
178     .job_type      = BLOCK_JOB_TYPE_COMMIT,
179     .set_speed     = commit_set_speed,
180 };
181 
182 void commit_start(BlockDriverState *bs, BlockDriverState *base,
183                   BlockDriverState *top, int64_t speed,
184                   BlockdevOnError on_error, BlockDriverCompletionFunc *cb,
185                   void *opaque, Error **errp)
186 {
187     CommitBlockJob *s;
188     BlockReopenQueue *reopen_queue = NULL;
189     int orig_overlay_flags;
190     int orig_base_flags;
191     BlockDriverState *overlay_bs;
192     Error *local_err = NULL;
193 
194     if ((on_error == BLOCKDEV_ON_ERROR_STOP ||
195          on_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
196         !bdrv_iostatus_is_enabled(bs)) {
197         error_setg(errp, "Invalid parameter combination");
198         return;
199     }
200 
201     assert(top != bs);
202     if (top == base) {
203         error_setg(errp, "Invalid files for merge: top and base are the same");
204         return;
205     }
206 
207     overlay_bs = bdrv_find_overlay(bs, top);
208 
209     if (overlay_bs == NULL) {
210         error_setg(errp, "Could not find overlay image for %s:", top->filename);
211         return;
212     }
213 
214     orig_base_flags    = bdrv_get_flags(base);
215     orig_overlay_flags = bdrv_get_flags(overlay_bs);
216 
217     /* convert base & overlay_bs to r/w, if necessary */
218     if (!(orig_base_flags & BDRV_O_RDWR)) {
219         reopen_queue = bdrv_reopen_queue(reopen_queue, base,
220                                          orig_base_flags | BDRV_O_RDWR);
221     }
222     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
223         reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs,
224                                          orig_overlay_flags | BDRV_O_RDWR);
225     }
226     if (reopen_queue) {
227         bdrv_reopen_multiple(reopen_queue, &local_err);
228         if (local_err != NULL) {
229             error_propagate(errp, local_err);
230             return;
231         }
232     }
233 
234 
235     s = block_job_create(&commit_job_driver, bs, speed, cb, opaque, errp);
236     if (!s) {
237         return;
238     }
239 
240     s->base   = base;
241     s->top    = top;
242     s->active = bs;
243 
244     s->base_flags          = orig_base_flags;
245     s->orig_overlay_flags  = orig_overlay_flags;
246 
247     s->on_error = on_error;
248     s->common.co = qemu_coroutine_create(commit_run);
249 
250     trace_commit_start(bs, base, top, s, s->common.co, opaque);
251     qemu_coroutine_enter(s->common.co, s);
252 }
253