block/commit.c

   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     char *backing_file_str;
  41 } CommitBlockJob;
  42
  43 static int coroutine_fn commit_populate(BlockDriverState *bs,
  44                                         BlockDriverState *base,
  45                                         int64_t sector_num, int nb_sectors,
  46                                         void *buf)
  47 {
  48     int ret = 0;
  49
  50     ret = bdrv_read(bs, sector_num, buf, nb_sectors);
  51     if (ret) {
  52         return ret;
  53     }
  54
  55     ret = bdrv_write(base, sector_num, buf, nb_sectors);
  56     if (ret) {
  57         return ret;
  58     }
  59
  60     return 0;
  61 }
  62
  63 typedef struct {
  64     int ret;
  65 } CommitCompleteData;
  66
  67 static void commit_complete(BlockJob *job, void *opaque)
  68 {
  69     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
  70     CommitCompleteData *data = opaque;
  71     BlockDriverState *active = s->active;
  72     BlockDriverState *top = s->top;
  73     BlockDriverState *base = s->base;
  74     BlockDriverState *overlay_bs;
  75     int ret = data->ret;
  76
  77     if (!block_job_is_cancelled(&s->common) && ret == 0) {
  78         /* success */
  79         ret = bdrv_drop_intermediate(active, top, base, s->backing_file_str);
  80     }
  81
  82     /* restore base open flags here if appropriate (e.g., change the base back
  83      * to r/o). These reopens do not need to be atomic, since we won't abort
  84      * even on failure here */
  85     if (s->base_flags != bdrv_get_flags(base)) {
  86         bdrv_reopen(base, s->base_flags, NULL);
  87     }
  88     overlay_bs = bdrv_find_overlay(active, top);
  89     if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
  90         bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);
  91     }
  92     g_free(s->backing_file_str);
  93     block_job_completed(&s->common, ret);
  94     g_free(data);
  95 }
  96
  97 static void coroutine_fn commit_run(void *opaque)
  98 {
  99     CommitBlockJob *s = opaque;
 100     CommitCompleteData *data;
 101     BlockDriverState *top = s->top;
 102     BlockDriverState *base = s->base;
 103     int64_t sector_num, end;
 104     int ret = 0;
 105     int n = 0;
 106     void *buf = NULL;
 107     int bytes_written = 0;
 108     int64_t base_len;
 109
 110     ret = s->common.len = bdrv_getlength(top);
 111
 112
 113     if (s->common.len < 0) {
 114         goto out;
 115     }
 116
 117     ret = base_len = bdrv_getlength(base);
 118     if (base_len < 0) {
 119         goto out;
 120     }
 121
 122     if (base_len < s->common.len) {
 123         ret = bdrv_truncate(base, s->common.len);
 124         if (ret) {
 125             goto out;
 126         }
 127     }
 128
 129     end = s->common.len >> BDRV_SECTOR_BITS;
 130     buf = qemu_blockalign(top, COMMIT_BUFFER_SIZE);
 131
 132     for (sector_num = 0; sector_num < end; sector_num += n) {
 133         uint64_t delay_ns = 0;
 134         bool copy;
 135
 136 wait:
 137         /* Note that even when no rate limit is applied we need to yield
 138          * with no pending I/O here so that bdrv_drain_all() returns.
 139          */
 140         block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
 141         if (block_job_is_cancelled(&s->common)) {
 142             break;
 143         }
 144         /* Copy if allocated above the base */
 145         ret = bdrv_is_allocated_above(top, base, sector_num,
 146                                       COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,
 147                                       &n);
 148         copy = (ret == 1);
 149         trace_commit_one_iteration(s, sector_num, n, ret);
 150         if (copy) {
 151             if (s->common.speed) {
 152                 delay_ns = ratelimit_calculate_delay(&s->limit, n);
 153                 if (delay_ns > 0) {
 154                     goto wait;
 155                 }
 156             }
 157             ret = commit_populate(top, base, sector_num, n, buf);
 158             bytes_written += n * BDRV_SECTOR_SIZE;
 159         }
 160         if (ret < 0) {
 161             if (s->on_error == BLOCKDEV_ON_ERROR_STOP ||
 162                 s->on_error == BLOCKDEV_ON_ERROR_REPORT||
 163                 (s->on_error == BLOCKDEV_ON_ERROR_ENOSPC && ret == -ENOSPC)) {
 164                 goto out;
 165             } else {
 166                 n = 0;
 167                 continue;
 168             }
 169         }
 170         /* Publish progress */
 171         s->common.offset += n * BDRV_SECTOR_SIZE;
 172     }
 173
 174     ret = 0;
 175
 176 out:
 177     qemu_vfree(buf);
 178
 179     data = g_malloc(sizeof(*data));
 180     data->ret = ret;
 181     block_job_defer_to_main_loop(&s->common, commit_complete, data);
 182 }
 183
 184 static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp)
 185 {
 186     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
 187
 188     if (speed < 0) {
 189         error_set(errp, QERR_INVALID_PARAMETER, "speed");
 190         return;
 191     }
 192     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
 193 }
 194
 195 static const BlockJobDriver commit_job_driver = {
 196     .instance_size = sizeof(CommitBlockJob),
 197     .job_type      = BLOCK_JOB_TYPE_COMMIT,
 198     .set_speed     = commit_set_speed,
 199 };
 200
 201 void commit_start(BlockDriverState *bs, BlockDriverState *base,
 202                   BlockDriverState *top, int64_t speed,
 203                   BlockdevOnError on_error, BlockCompletionFunc *cb,
 204                   void *opaque, const char *backing_file_str, Error **errp)
 205 {
 206     CommitBlockJob *s;
 207     BlockReopenQueue *reopen_queue = NULL;
 208     int orig_overlay_flags;
 209     int orig_base_flags;
 210     BlockDriverState *overlay_bs;
 211     Error *local_err = NULL;
 212
 213     if ((on_error == BLOCKDEV_ON_ERROR_STOP ||
 214          on_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
 215         !bdrv_iostatus_is_enabled(bs)) {
 216         error_setg(errp, "Invalid parameter combination");
 217         return;
 218     }
 219
 220     assert(top != bs);
 221     if (top == base) {
 222         error_setg(errp, "Invalid files for merge: top and base are the same");
 223         return;
 224     }
 225
 226     overlay_bs = bdrv_find_overlay(bs, top);
 227
 228     if (overlay_bs == NULL) {
 229         error_setg(errp, "Could not find overlay image for %s:", top->filename);
 230         return;
 231     }
 232
 233     orig_base_flags    = bdrv_get_flags(base);
 234     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 235
 236     /* convert base & overlay_bs to r/w, if necessary */
 237     if (!(orig_base_flags & BDRV_O_RDWR)) {
 238         reopen_queue = bdrv_reopen_queue(reopen_queue, base,
 239                                          orig_base_flags | BDRV_O_RDWR);
 240     }
 241     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
 242         reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs,
 243                                          orig_overlay_flags | BDRV_O_RDWR);
 244     }
 245     if (reopen_queue) {
 246         bdrv_reopen_multiple(reopen_queue, &local_err);
 247         if (local_err != NULL) {
 248             error_propagate(errp, local_err);
 249             return;
 250         }
 251     }
 252
 253
 254     s = block_job_create(&commit_job_driver, bs, speed, cb, opaque, errp);
 255     if (!s) {
 256         return;
 257     }
 258
 259     s->base   = base;
 260     s->top    = top;
 261     s->active = bs;
 262
 263     s->base_flags          = orig_base_flags;
 264     s->orig_overlay_flags  = orig_overlay_flags;
 265
 266     s->backing_file_str = g_strdup(backing_file_str);
 267
 268     s->on_error = on_error;
 269     s->common.co = qemu_coroutine_create(commit_run);
 270
 271     trace_commit_start(bs, base, top, s, s->common.co, opaque);
 272     qemu_coroutine_enter(s->common.co, s);
 273 }