Commit 678ba275 authored by Eric Blake's avatar Eric Blake
Browse files

nbd: Merge nbd_export_bitmap into nbd_export_new 



We only have one caller that wants to export a bitmap name,
which it does right after creation of the export. But there is
still a brief window of time where an NBD client could see the
export but not the dirty bitmap, which a robust client would
have to interpret as meaning the entire image should be treated
as dirty.  Better is to eliminate the window entirely, by
inlining nbd_export_bitmap() into nbd_export_new(), and refusing
to create the bitmap in the first place if the requested bitmap
can't be located.

We also no longer need logic for setting a different bitmap
name compared to the bitmap being exported.

Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190111194720.15671-8-eblake@redhat.com>
parent 7dc570b3

blockdev-nbd.c

+1 −10
Original line number Diff line number Diff line
@@ -175,7 +175,7 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name, 
        writable = false;

    }



    exp = nbd_export_new(bs, 0, -1, name, NULL,

    exp = nbd_export_new(bs, 0, -1, name, NULL, bitmap,

                         writable ? 0 : NBD_FLAG_READ_ONLY,

                         NULL, false, on_eject_blk, errp);

    if (!exp) {
@@ -186,15 +186,6 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name, 
     * our only way of accessing it is through nbd_export_find(), so we can drop

     * the strong reference that is @exp. */

    nbd_export_put(exp);



    if (has_bitmap) {

        Error *err = NULL;

        nbd_export_bitmap(exp, bitmap, bitmap, &err);

        if (err) {

            error_propagate(errp, err);

            nbd_export_remove(exp, NBD_SERVER_REMOVE_MODE_HARD, NULL);

        }

    }

}



void qmp_nbd_server_remove(const char *name,

include/block/nbd.h

+3 −6
Original line number Diff line number Diff line
@@ -296,9 +296,9 @@ typedef struct NBDClient NBDClient; 


NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,

                          const char *name, const char *description,

                          uint16_t nbdflags, void (*close)(NBDExport *),

                          bool writethrough, BlockBackend *on_eject_blk,

                          Error **errp);

                          const char *bitmap, uint16_t nbdflags,

                          void (*close)(NBDExport *), bool writethrough,

                          BlockBackend *on_eject_blk, Error **errp);

void nbd_export_close(NBDExport *exp);

void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp);

void nbd_export_get(NBDExport *exp);
@@ -319,9 +319,6 @@ void nbd_client_put(NBDClient *client); 
void nbd_server_start(SocketAddress *addr, const char *tls_creds,

                      Error **errp);



void nbd_export_bitmap(NBDExport *exp, const char *bitmap,

                       const char *bitmap_export_name, Error **errp);



/* nbd_read

 * Reads @size bytes from @ioc. Returns 0 on success.

 */

nbd/server.c

+40 −47
Original line number Diff line number Diff line
@@ -1457,9 +1457,9 @@ static void nbd_eject_notifier(Notifier *n, void *data) 


NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,

                          const char *name, const char *description,

                          uint16_t nbdflags, void (*close)(NBDExport *),

                          bool writethrough, BlockBackend *on_eject_blk,

                          Error **errp)

                          const char *bitmap, uint16_t nbdflags,

                          void (*close)(NBDExport *), bool writethrough,

                          BlockBackend *on_eject_blk, Error **errp)

{

    AioContext *ctx;

    BlockBackend *blk;
@@ -1507,6 +1507,43 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size, 
    }

    exp->size -= exp->size % BDRV_SECTOR_SIZE;



    if (bitmap) {

        BdrvDirtyBitmap *bm = NULL;

        BlockDriverState *bs = blk_bs(blk);



        while (true) {

            bm = bdrv_find_dirty_bitmap(bs, bitmap);

            if (bm != NULL || bs->backing == NULL) {

                break;

            }



            bs = bs->backing->bs;

        }



        if (bm == NULL) {

            error_setg(errp, "Bitmap '%s' is not found", bitmap);

            goto fail;

        }



        if ((nbdflags & NBD_FLAG_READ_ONLY) && bdrv_is_writable(bs) &&

            bdrv_dirty_bitmap_enabled(bm)) {

            error_setg(errp,

                       "Enabled bitmap '%s' incompatible with readonly export",

                       bitmap);

            goto fail;

        }



        if (bdrv_dirty_bitmap_user_locked(bm)) {

            error_setg(errp, "Bitmap '%s' is in use", bitmap);

            goto fail;

        }



        bdrv_dirty_bitmap_set_qmp_locked(bm, true);

        exp->export_bitmap = bm;

        exp->export_bitmap_context = g_strdup_printf("qemu:dirty-bitmap:%s",

                                                     bitmap);

    }



    exp->close = close;

    exp->ctx = blk_get_aio_context(blk);

    blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
@@ -2424,47 +2461,3 @@ void nbd_client_new(QIOChannelSocket *sioc, 
    co = qemu_coroutine_create(nbd_co_client_start, client);

    qemu_coroutine_enter(co);

}
 


void nbd_export_bitmap(NBDExport *exp, const char *bitmap,

                       const char *bitmap_export_name, Error **errp)

{

    BdrvDirtyBitmap *bm = NULL;

    BlockDriverState *bs = blk_bs(exp->blk);



    if (exp->export_bitmap) {

        error_setg(errp, "Export bitmap is already set");

        return;

    }



    while (true) {

        bm = bdrv_find_dirty_bitmap(bs, bitmap);

        if (bm != NULL || bs->backing == NULL) {

            break;

        }



        bs = bs->backing->bs;

    }



    if (bm == NULL) {

        error_setg(errp, "Bitmap '%s' is not found", bitmap);

        return;

    }



    if ((exp->nbdflags & NBD_FLAG_READ_ONLY) && bdrv_is_writable(bs) &&

        bdrv_dirty_bitmap_enabled(bm)) {

        error_setg(errp,

                   "Enabled bitmap '%s' incompatible with readonly export",

                   bitmap);

        return;

    }



    if (bdrv_dirty_bitmap_user_locked(bm)) {

        error_setg(errp, "Bitmap '%s' is in use", bitmap);

        return;

    }



    bdrv_dirty_bitmap_set_qmp_locked(bm, true);

    exp->export_bitmap = bm;

    exp->export_bitmap_context =

            g_strdup_printf("qemu:dirty-bitmap:%s", bitmap_export_name);

}

qemu-nbd.c

+3 −2
Original line number Diff line number Diff line
@@ -1016,8 +1016,9 @@ int main(int argc, char **argv) 
    }



    export = nbd_export_new(bs, dev_offset, fd_size, export_name,

                            export_description, nbdflags, nbd_export_closed,

                            writethrough, NULL, &error_fatal);

                            export_description, NULL, nbdflags,

                            nbd_export_closed, writethrough, NULL,

                            &error_fatal);



    if (device) {

#if HAVE_NBD_DEVICE