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 "qemu/osdep.h"
  16 #include "trace.h"
  17 #include "block/block_int.h"
  18 #include "block/blockjob.h"
  19 #include "qapi/qmp/qerror.h"
  20 #include "qemu/ratelimit.h"
  21 #include "sysemu/block-backend.h"
  22
  23 enum {
  24     /*
  25      * Size of data buffer for populating the image file.  This should be large
  26      * enough to process multiple clusters in a single call, so that populating
  27      * contiguous regions of the image is efficient.
  28      */
  29     COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */
  30 };
  31
  32 #define SLICE_TIME 100000000ULL /* ns */
  33
  34 typedef struct CommitBlockJob {
  35     BlockJob common;
  36     RateLimit limit;
  37     BlockDriverState *active;
  38     BlockDriverState *top;
  39     BlockDriverState *base;
  40     BlockdevOnError on_error;
  41     int base_flags;
  42     int orig_overlay_flags;
  43     char *backing_file_str;
  44 } CommitBlockJob;
  45
  46 static int coroutine_fn commit_populate(BlockDriverState *bs,
  47                                         BlockDriverState *base,
  48                                         int64_t sector_num, int nb_sectors,
  49                                         void *buf)
  50 {
  51     int ret = 0;
  52
  53     ret = bdrv_read(bs, sector_num, buf, nb_sectors);
  54     if (ret) {
  55         return ret;
  56     }
  57
  58     ret = bdrv_write(base, sector_num, buf, nb_sectors);
  59     if (ret) {
  60         return ret;
  61     }
  62
  63     return 0;
  64 }
  65
  66 typedef struct {
  67     int ret;
  68 } CommitCompleteData;
  69
  70 static void commit_complete(BlockJob *job, void *opaque)
  71 {
  72     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
  73     CommitCompleteData *data = opaque;
  74     BlockDriverState *active = s->active;
  75     BlockDriverState *top = s->top;
  76     BlockDriverState *base = s->base;
  77     BlockDriverState *overlay_bs;
  78     int ret = data->ret;
  79
  80     if (!block_job_is_cancelled(&s->common) && ret == 0) {
  81         /* success */
  82         ret = bdrv_drop_intermediate(active, top, base, s->backing_file_str);
  83     }
  84
  85     /* restore base open flags here if appropriate (e.g., change the base back
  86      * to r/o). These reopens do not need to be atomic, since we won't abort
  87      * even on failure here */
  88     if (s->base_flags != bdrv_get_flags(base)) {
  89         bdrv_reopen(base, s->base_flags, NULL);
  90     }
  91     overlay_bs = bdrv_find_overlay(active, top);
  92     if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
  93         bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);
  94     }
  95     g_free(s->backing_file_str);
  96     block_job_completed(&s->common, ret);
  97     g_free(data);
  98 }
  99
 100 static void coroutine_fn commit_run(void *opaque)
 101 {
 102     CommitBlockJob *s = opaque;
 103     CommitCompleteData *data;
 104     BlockDriverState *top = s->top;
 105     BlockDriverState *base = s->base;
 106     int64_t sector_num, end;
 107     int ret = 0;
 108     int n = 0;
 109     void *buf = NULL;
 110     int bytes_written = 0;
 111     int64_t base_len;
 112
 113     ret = s->common.len = bdrv_getlength(top);
 114
 115
 116     if (s->common.len < 0) {
 117         goto out;
 118     }
 119
 120     ret = base_len = bdrv_getlength(base);
 121     if (base_len < 0) {
 122         goto out;
 123     }
 124
 125     if (base_len < s->common.len) {
 126         ret = bdrv_truncate(base, s->common.len);
 127         if (ret) {
 128             goto out;
 129         }
 130     }
 131
 132     end = s->common.len >> BDRV_SECTOR_BITS;
 133     buf = qemu_blockalign(top, COMMIT_BUFFER_SIZE);
 134
 135     for (sector_num = 0; sector_num < end; sector_num += n) {
 136         uint64_t delay_ns = 0;
 137         bool copy;
 138
 139 wait:
 140         /* Note that even when no rate limit is applied we need to yield
 141          * with no pending I/O here so that bdrv_drain_all() returns.
 142          */
 143         block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
 144         if (block_job_is_cancelled(&s->common)) {
 145             break;
 146         }
 147         /* Copy if allocated above the base */
 148         ret = bdrv_is_allocated_above(top, base, sector_num,
 149                                       COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,
 150                                       &n);
 151         copy = (ret == 1);
 152         trace_commit_one_iteration(s, sector_num, n, ret);
 153         if (copy) {
 154             if (s->common.speed) {
 155                 delay_ns = ratelimit_calculate_delay(&s->limit, n);
 156                 if (delay_ns > 0) {
 157                     goto wait;
 158                 }
 159             }
 160             ret = commit_populate(top, base, sector_num, n, buf);
 161             bytes_written += n * BDRV_SECTOR_SIZE;
 162         }
 163         if (ret < 0) {
 164             if (s->on_error == BLOCKDEV_ON_ERROR_STOP ||
 165                 s->on_error == BLOCKDEV_ON_ERROR_REPORT||
 166                 (s->on_error == BLOCKDEV_ON_ERROR_ENOSPC && ret == -ENOSPC)) {
 167                 goto out;
 168             } else {
 169                 n = 0;
 170                 continue;
 171             }
 172         }
 173         /* Publish progress */
 174         s->common.offset += n * BDRV_SECTOR_SIZE;
 175     }
 176
 177     ret = 0;
 178
 179 out:
 180     qemu_vfree(buf);
 181
 182     data = g_malloc(sizeof(*data));
 183     data->ret = ret;
 184     block_job_defer_to_main_loop(&s->common, commit_complete, data);
 185 }
 186
 187 static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp)
 188 {
 189     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
 190
 191     if (speed < 0) {
 192         error_setg(errp, QERR_INVALID_PARAMETER, "speed");
 193         return;
 194     }
 195     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
 196 }
 197
 198 static const BlockJobDriver commit_job_driver = {
 199     .instance_size = sizeof(CommitBlockJob),
 200     .job_type      = BLOCK_JOB_TYPE_COMMIT,
 201     .set_speed     = commit_set_speed,
 202 };
 203
 204 void commit_start(BlockDriverState *bs, BlockDriverState *base,
 205                   BlockDriverState *top, int64_t speed,
 206                   BlockdevOnError on_error, BlockCompletionFunc *cb,
 207                   void *opaque, const char *backing_file_str, Error **errp)
 208 {
 209     CommitBlockJob *s;
 210     BlockReopenQueue *reopen_queue = NULL;
 211     int orig_overlay_flags;
 212     int orig_base_flags;
 213     BlockDriverState *overlay_bs;
 214     Error *local_err = NULL;
 215
 216     if ((on_error == BLOCKDEV_ON_ERROR_STOP ||
 217          on_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
 218         (!bs->blk || !blk_iostatus_is_enabled(bs->blk))) {
 219         error_setg(errp, "Invalid parameter combination");
 220         return;
 221     }
 222
 223     assert(top != bs);
 224     if (top == base) {
 225         error_setg(errp, "Invalid files for merge: top and base are the same");
 226         return;
 227     }
 228
 229     overlay_bs = bdrv_find_overlay(bs, top);
 230
 231     if (overlay_bs == NULL) {
 232         error_setg(errp, "Could not find overlay image for %s:", top->filename);
 233         return;
 234     }
 235
 236     orig_base_flags    = bdrv_get_flags(base);
 237     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 238
 239     /* convert base & overlay_bs to r/w, if necessary */
 240     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
 241         reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL,
 242                                          orig_overlay_flags | BDRV_O_RDWR);
 243     }
 244     if (!(orig_base_flags & BDRV_O_RDWR)) {
 245         reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL,
 246                                          orig_base_flags | BDRV_O_RDWR);
 247     }
 248     if (reopen_queue) {
 249         bdrv_reopen_multiple(reopen_queue, &local_err);
 250         if (local_err != NULL) {
 251             error_propagate(errp, local_err);
 252             return;
 253         }
 254     }
 255
 256
 257     s = block_job_create(&commit_job_driver, bs, speed, cb, opaque, errp);
 258     if (!s) {
 259         return;
 260     }
 261
 262     s->base   = base;
 263     s->top    = top;
 264     s->active = bs;
 265
 266     s->base_flags          = orig_base_flags;
 267     s->orig_overlay_flags  = orig_overlay_flags;
 268
 269     s->backing_file_str = g_strdup(backing_file_str);
 270
 271     s->on_error = on_error;
 272     s->common.co = qemu_coroutine_create(commit_run);
 273
 274     trace_commit_start(bs, base, top, s, s->common.co, opaque);
 275     qemu_coroutine_enter(s->common.co, s);
 276 }