Commit 74da6b94 authored by John Snow's avatar John Snow
Browse files

block/dirty-bitmaps: implement inconsistent bit 



Set the inconsistent bit on load instead of rejecting such bitmaps.
There is no way to un-set it; the only option is to delete the bitmap.

Obvervations:
- bitmap loading does not need to update the header for in_use bitmaps.
- inconsistent bitmaps don't need to have their data loaded; they're
  glorified corruption sentinels.
- bitmap saving does not need to save inconsistent bitmaps back to disk.
- bitmap reopening DOES need to drop the readonly flag from inconsistent
  bitmaps to allow reopening of qcow2 files with non-qemu-owned bitmaps
  being eventually flushed back to disk.

Signed-off-by: default avatarJohn Snow <jsnow@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Message-id: 20190301191545.8728-8-jsnow@redhat.com
Signed-off-by: default avatarJohn Snow <jsnow@redhat.com>
parent cb8e58e3

block/qcow2-bitmap.c

+51 −48
Original line number Diff line number Diff line
@@ -343,11 +343,17 @@ static BdrvDirtyBitmap *load_bitmap(BlockDriverState *bs, 
    uint32_t granularity;

    BdrvDirtyBitmap *bitmap = NULL;



    if (bm->flags & BME_FLAG_IN_USE) {

        error_setg(errp, "Bitmap '%s' is in use", bm->name);

    granularity = 1U << bm->granularity_bits;

    bitmap = bdrv_create_dirty_bitmap(bs, granularity, bm->name, errp);

    if (bitmap == NULL) {

        goto fail;

    }



    if (bm->flags & BME_FLAG_IN_USE) {

        /* Data is unusable, skip loading it */

        return bitmap;

    }



    ret = bitmap_table_load(bs, &bm->table, &bitmap_table);

    if (ret < 0) {

        error_setg_errno(errp, -ret,
@@ -356,12 +362,6 @@ static BdrvDirtyBitmap *load_bitmap(BlockDriverState *bs, 
        goto fail;

    }



    granularity = 1U << bm->granularity_bits;

    bitmap = bdrv_create_dirty_bitmap(bs, granularity, bm->name, errp);

    if (bitmap == NULL) {

        goto fail;

    }



    ret = load_bitmap_data(bs, bitmap_table, bm->table.size, bitmap);

    if (ret < 0) {

        error_setg_errno(errp, -ret, "Could not read bitmap '%s' from image",
@@ -950,6 +950,7 @@ bool qcow2_load_dirty_bitmaps(BlockDriverState *bs, Error **errp) 
    Qcow2Bitmap *bm;

    GSList *created_dirty_bitmaps = NULL;

    bool header_updated = false;

    bool needs_update = false;



    if (s->nb_bitmaps == 0) {

        /* No bitmaps - nothing to do */
@@ -963,24 +964,27 @@ bool qcow2_load_dirty_bitmaps(BlockDriverState *bs, Error **errp) 
    }



    QSIMPLEQ_FOREACH(bm, bm_list, entry) {

        if (!(bm->flags & BME_FLAG_IN_USE)) {

        BdrvDirtyBitmap *bitmap = load_bitmap(bs, bm, errp);

        if (bitmap == NULL) {

            goto fail;

        }



        bdrv_dirty_bitmap_set_persistance(bitmap, true);

        if (bm->flags & BME_FLAG_IN_USE) {

            bdrv_dirty_bitmap_set_inconsistent(bitmap);

        } else {

            /* NB: updated flags only get written if can_write(bs) is true. */

            bm->flags |= BME_FLAG_IN_USE;

            needs_update = true;

        }

        if (!(bm->flags & BME_FLAG_AUTO)) {

            bdrv_disable_dirty_bitmap(bitmap);

        }

            bdrv_dirty_bitmap_set_persistance(bitmap, true);

            bm->flags |= BME_FLAG_IN_USE;

        created_dirty_bitmaps =

            g_slist_append(created_dirty_bitmaps, bitmap);

    }

    }



    if (created_dirty_bitmaps != NULL) {

        if (can_write(bs)) {

    if (needs_update && can_write(bs)) {

        /* in_use flags must be updated */

        int ret = update_ext_header_and_dir_in_place(bs, bm_list);

        if (ret < 0) {
@@ -988,11 +992,12 @@ bool qcow2_load_dirty_bitmaps(BlockDriverState *bs, Error **errp) 
            goto fail;

        }

        header_updated = true;

        } else {

    }



    if (!can_write(bs)) {

        g_slist_foreach(created_dirty_bitmaps, set_readonly_helper,

                        (gpointer)true);

    }

    }



    g_slist_free(created_dirty_bitmaps);

    bitmap_list_free(bm_list);
@@ -1113,16 +1118,15 @@ int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs, bool *header_updated, 
    }



    QSIMPLEQ_FOREACH(bm, bm_list, entry) {

        if (!(bm->flags & BME_FLAG_IN_USE)) {

        BdrvDirtyBitmap *bitmap = bdrv_find_dirty_bitmap(bs, bm->name);

        if (bitmap == NULL) {

            continue;

        }



        if (!bdrv_dirty_bitmap_readonly(bitmap)) {

                error_setg(errp, "Bitmap %s is not readonly but not marked"

                                 "'IN_USE' in the image. Something went wrong,"

                                 "all the bitmaps may be corrupted", bm->name);

            error_setg(errp, "Bitmap %s was loaded prior to rw-reopen, but was "

                       "not marked as readonly. This is a bug, something went "

                       "wrong. All of the bitmaps may be corrupted", bm->name);

            ret = -EINVAL;

            goto out;

        }
@@ -1130,7 +1134,6 @@ int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs, bool *header_updated, 
        bm->flags |= BME_FLAG_IN_USE;

        ro_dirty_bitmaps = g_slist_append(ro_dirty_bitmaps, bitmap);

    }

    }



    if (ro_dirty_bitmaps != NULL) {

        /* in_use flags must be updated */
@@ -1425,8 +1428,8 @@ void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp) 
        Qcow2Bitmap *bm;



        if (!bdrv_dirty_bitmap_get_persistance(bitmap) ||

            bdrv_dirty_bitmap_readonly(bitmap))

        {

            bdrv_dirty_bitmap_readonly(bitmap) ||

            bdrv_dirty_bitmap_inconsistent(bitmap)) {

            continue;

        }