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 } 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, rt_clock, delay_ns);
 107         if (block_job_is_cancelled(&s->common)) {
 108             break;
 109         }
 110         /* Copy if allocated above the base */
 111         ret = bdrv_co_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 BlockJobType commit_job_type = {
 177     .instance_size = sizeof(CommitBlockJob),
 178     .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_set(errp, QERR_INVALID_PARAMETER_COMBINATION);
 198         return;
 199     }
 200
 201     /* Once we support top == active layer, remove this check */
 202     if (top == bs) {
 203         error_setg(errp,
 204                    "Top image as the active layer is currently unsupported");
 205         return;
 206     }
 207
 208     if (top == base) {
 209         error_setg(errp, "Invalid files for merge: top and base are the same");
 210         return;
 211     }
 212
 213     overlay_bs = bdrv_find_overlay(bs, top);
 214
 215     if (overlay_bs == NULL) {
 216         error_setg(errp, "Could not find overlay image for %s:", top->filename);
 217         return;
 218     }
 219
 220     orig_base_flags    = bdrv_get_flags(base);
 221     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 222
 223     /* convert base & overlay_bs to r/w, if necessary */
 224     if (!(orig_base_flags & BDRV_O_RDWR)) {
 225         reopen_queue = bdrv_reopen_queue(reopen_queue, base,
 226                                          orig_base_flags | BDRV_O_RDWR);
 227     }
 228     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
 229         reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs,
 230                                          orig_overlay_flags | BDRV_O_RDWR);
 231     }
 232     if (reopen_queue) {
 233         bdrv_reopen_multiple(reopen_queue, &local_err);
 234         if (local_err != NULL) {
 235             error_propagate(errp, local_err);
 236             return;
 237         }
 238     }
 239
 240
 241     s = block_job_create(&commit_job_type, bs, speed, cb, opaque, errp);
 242     if (!s) {
 243         return;
 244     }
 245
 246     s->base   = base;
 247     s->top    = top;
 248     s->active = bs;
 249
 250     s->base_flags          = orig_base_flags;
 251     s->orig_overlay_flags  = orig_overlay_flags;
 252
 253     s->on_error = on_error;
 254     s->common.co = qemu_coroutine_create(commit_run);
 255
 256     trace_commit_start(bs, base, top, s, s->common.co, opaque);
 257     qemu_coroutine_enter(s->common.co, s);
 258 }