mirror of https://github.com/proxmox/mirror_qemu
block: Ignore guest dev permissions during incoming migration
Usually guest devices don't like other writers to the same image, so they use blk_set_perm() to prevent this from happening. In the migration phase before the VM is actually running, though, they don't have a problem with writes to the image. On the other hand, storage migration needs to be able to write to the image in this phase, so the restrictive blk_set_perm() call of qdev devices breaks it. This patch flags all BlockBackends with a qdev device as blk->disable_perm during incoming migration, which means that the requested permissions are stored in the BlockBackend, but not actually applied to its root node yet. Once migration has finished and the VM should be resumed, the permissions are applied. If they cannot be applied (e.g. because the NBD server used for block migration hasn't been shut down), resuming the VM fails. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Tested-by: Kashyap Chamarthy <kchamart@redhat.com>master
parent
5fe2339e6b
commit
d35ff5e6b3
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@ -61,6 +61,7 @@ struct BlockBackend {
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uint64_t perm;
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uint64_t perm;
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uint64_t shared_perm;
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uint64_t shared_perm;
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bool disable_perm;
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bool allow_write_beyond_eof;
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bool allow_write_beyond_eof;
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@ -578,7 +579,7 @@ int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm,
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{
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{
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int ret;
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int ret;
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if (blk->root) {
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if (blk->root && !blk->disable_perm) {
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ret = bdrv_child_try_set_perm(blk->root, perm, shared_perm, errp);
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ret = bdrv_child_try_set_perm(blk->root, perm, shared_perm, errp);
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if (ret < 0) {
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if (ret < 0) {
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return ret;
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return ret;
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@ -597,15 +598,52 @@ void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm)
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*shared_perm = blk->shared_perm;
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*shared_perm = blk->shared_perm;
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}
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}
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/*
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* Notifies the user of all BlockBackends that migration has completed. qdev
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* devices can tighten their permissions in response (specifically revoke
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* shared write permissions that we needed for storage migration).
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*
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* If an error is returned, the VM cannot be allowed to be resumed.
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*/
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void blk_resume_after_migration(Error **errp)
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{
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BlockBackend *blk;
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Error *local_err = NULL;
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for (blk = blk_all_next(NULL); blk; blk = blk_all_next(blk)) {
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if (!blk->disable_perm) {
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continue;
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}
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blk->disable_perm = false;
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blk_set_perm(blk, blk->perm, blk->shared_perm, &local_err);
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if (local_err) {
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error_propagate(errp, local_err);
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blk->disable_perm = true;
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return;
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}
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}
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}
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static int blk_do_attach_dev(BlockBackend *blk, void *dev)
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static int blk_do_attach_dev(BlockBackend *blk, void *dev)
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{
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{
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if (blk->dev) {
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if (blk->dev) {
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return -EBUSY;
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return -EBUSY;
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}
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}
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/* While migration is still incoming, we don't need to apply the
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* permissions of guest device BlockBackends. We might still have a block
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* job or NBD server writing to the image for storage migration. */
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if (runstate_check(RUN_STATE_INMIGRATE)) {
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blk->disable_perm = true;
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}
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blk_ref(blk);
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blk_ref(blk);
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blk->dev = dev;
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blk->dev = dev;
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blk->legacy_dev = false;
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blk->legacy_dev = false;
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blk_iostatus_reset(blk);
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blk_iostatus_reset(blk);
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return 0;
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return 0;
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}
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}
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@ -366,6 +366,8 @@ void bdrv_invalidate_cache(BlockDriverState *bs, Error **errp);
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void bdrv_invalidate_cache_all(Error **errp);
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void bdrv_invalidate_cache_all(Error **errp);
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int bdrv_inactivate_all(void);
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int bdrv_inactivate_all(void);
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void blk_resume_after_migration(Error **errp);
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/* Ensure contents are flushed to disk. */
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/* Ensure contents are flushed to disk. */
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int bdrv_flush(BlockDriverState *bs);
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int bdrv_flush(BlockDriverState *bs);
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int coroutine_fn bdrv_co_flush(BlockDriverState *bs);
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int coroutine_fn bdrv_co_flush(BlockDriverState *bs);
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@ -349,6 +349,14 @@ static void process_incoming_migration_bh(void *opaque)
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exit(EXIT_FAILURE);
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exit(EXIT_FAILURE);
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}
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}
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/* If we get an error here, just don't restart the VM yet. */
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blk_resume_after_migration(&local_err);
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if (local_err) {
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error_free(local_err);
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local_err = NULL;
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autostart = false;
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}
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/*
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/*
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* This must happen after all error conditions are dealt with and
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* This must happen after all error conditions are dealt with and
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* we're sure the VM is going to be running on this host.
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* we're sure the VM is going to be running on this host.
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6
qmp.c
6
qmp.c
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@ -207,6 +207,12 @@ void qmp_cont(Error **errp)
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}
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}
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}
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}
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blk_resume_after_migration(&local_err);
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if (local_err) {
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error_propagate(errp, local_err);
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return;
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}
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if (runstate_check(RUN_STATE_INMIGRATE)) {
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if (runstate_check(RUN_STATE_INMIGRATE)) {
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autostart = 1;
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autostart = 1;
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} else {
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} else {
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