Commit 1a2b8b40 authored by John Snow's avatar John Snow
Browse files

block/backup: support bitmap sync modes for non-bitmap backups 



Accept bitmaps and sync policies for the other backup modes.
This allows us to do things like create a bitmap synced to a full backup
without a transaction, or start a resumable backup process.

Some combinations don't make sense, though:

- NEVER policy combined with any non-BITMAP mode doesn't do anything,
  because the bitmap isn't used for input or output.
  It's harmless, but is almost certainly never what the user wanted.

- sync=NONE is more questionable. It can't use on-success because this
  job never completes with success anyway, and the resulting artifact
  of 'always' is suspect: because we start with a full bitmap and only
  copy out segments that get written to, the final output bitmap will
  always be ... a fully set bitmap.

  Maybe there's contexts in which bitmaps make sense for sync=none,
  but not without more severe changes to the current job, and omitting
  it here doesn't prevent us from adding it later.

Signed-off-by: default avatarJohn Snow <jsnow@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
Message-id: 20190716000117.25219-11-jsnow@redhat.com
Signed-off-by: default avatarJohn Snow <jsnow@redhat.com>
parent 7e30dd61

block/backup.c

+1 −7
Original line number Diff line number Diff line
@@ -697,7 +697,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, 
        return NULL;

    }



    if (sync_mode == MIRROR_SYNC_MODE_BITMAP) {

    if (sync_bitmap) {

        /* If we need to write to this bitmap, check that we can: */

        if (bitmap_mode != BITMAP_SYNC_MODE_NEVER &&

            bdrv_dirty_bitmap_check(sync_bitmap, BDRV_BITMAP_DEFAULT, errp)) {
@@ -708,12 +708,6 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, 
        if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) {

            return NULL;

        }

    } else if (sync_bitmap) {

        error_setg(errp,

                   "a bitmap was given to backup_job_create, "

                   "but it received an incompatible sync_mode (%s)",

                   MirrorSyncMode_str(sync_mode));

        return NULL;

    }



    len = bdrv_getlength(bs);

blockdev.c

+22 −0
Original line number Diff line number Diff line
@@ -3567,6 +3567,28 @@ static BlockJob *do_backup_common(BackupCommon *backup, 
        if (bdrv_dirty_bitmap_check(bmap, BDRV_BITMAP_ALLOW_RO, errp)) {

            return NULL;

        }



        /* This does not produce a useful bitmap artifact: */

        if (backup->sync == MIRROR_SYNC_MODE_NONE) {

            error_setg(errp, "sync mode '%s' does not produce meaningful bitmap"

                       " outputs", MirrorSyncMode_str(backup->sync));

            return NULL;

        }



        /* If the bitmap isn't used for input or output, this is useless: */

        if (backup->bitmap_mode == BITMAP_SYNC_MODE_NEVER &&

            backup->sync != MIRROR_SYNC_MODE_BITMAP) {

            error_setg(errp, "Bitmap sync mode '%s' has no meaningful effect"

                       " when combined with sync mode '%s'",

                       BitmapSyncMode_str(backup->bitmap_mode),

                       MirrorSyncMode_str(backup->sync));

            return NULL;

        }

    }



    if (!backup->has_bitmap && backup->has_bitmap_mode) {

        error_setg(errp, "Cannot specify bitmap sync mode without a bitmap");

        return NULL;

    }



    if (!backup->auto_finalize) {

qapi/block-core.json

+4 −2
Original line number Diff line number Diff line
@@ -1352,13 +1352,15 @@ 
# @speed: the maximum speed, in bytes per second. The default is 0,

#         for unlimited.

#

# @bitmap: the name of a dirty bitmap if sync is "bitmap" or "incremental".

# @bitmap: The name of a dirty bitmap to use.

#          Must be present if sync is "bitmap" or "incremental".

#          Can be present if sync is "full" or "top".

#          Must not be present otherwise.

#          (Since 2.4 (drive-backup), 3.1 (blockdev-backup))

#

# @bitmap-mode: Specifies the type of data the bitmap should contain after

#               the operation concludes. Must be present if sync is "bitmap".

#               the operation concludes.

#               Must be present if a bitmap was provided,

#               Must NOT be present otherwise. (Since 4.2)

#

# @compress: true to compress data, if the target format supports it.