diff options
| -rw-r--r-- | block.c | 166 | ||||
| -rw-r--r-- | include/block/block.h | 2 |
2 files changed, 168 insertions, 0 deletions
@@ -2984,6 +2984,27 @@ BlockDriverState *bdrv_open(const char *filename, const char *reference, } /* + * Returns true if @child can be reached recursively from @bs + */ +static bool bdrv_recurse_has_child(BlockDriverState *bs, + BlockDriverState *child) +{ + BdrvChild *c; + + if (bs == child) { + return true; + } + + QLIST_FOREACH(c, &bs->children, next) { + if (bdrv_recurse_has_child(c->bs, child)) { + return true; + } + } + + return false; +} + +/* * Adds a BlockDriverState to a simple queue for an atomic, transactional * reopen of multiple devices. * @@ -3208,6 +3229,19 @@ int bdrv_reopen_multiple(AioContext *ctx, BlockReopenQueue *bs_queue, Error **er if (ret < 0) { goto cleanup_perm; } + /* Check if new_backing_bs would accept the new permissions */ + if (state->replace_backing_bs && state->new_backing_bs) { + uint64_t nperm, nshared; + bdrv_child_perm(state->bs, state->new_backing_bs, + NULL, &child_backing, bs_queue, + state->perm, state->shared_perm, + &nperm, &nshared); + ret = bdrv_check_update_perm(state->new_backing_bs, NULL, + nperm, nshared, NULL, errp); + if (ret < 0) { + goto cleanup_perm; + } + } bs_entry->perms_checked = true; } @@ -3231,6 +3265,9 @@ cleanup_perm: bdrv_set_perm(state->bs, state->perm, state->shared_perm); } else { bdrv_abort_perm_update(state->bs); + if (state->replace_backing_bs && state->new_backing_bs) { + bdrv_abort_perm_update(state->new_backing_bs); + } } } cleanup: @@ -3242,6 +3279,9 @@ cleanup: qobject_unref(bs_entry->state.explicit_options); qobject_unref(bs_entry->state.options); } + if (bs_entry->state.new_backing_bs) { + bdrv_unref(bs_entry->state.new_backing_bs); + } g_free(bs_entry); } g_free(bs_queue); @@ -3314,6 +3354,101 @@ static void bdrv_reopen_perm(BlockReopenQueue *q, BlockDriverState *bs, } /* + * Take a BDRVReopenState and check if the value of 'backing' in the + * reopen_state->options QDict is valid or not. + * + * If 'backing' is missing from the QDict then return 0. + * + * If 'backing' contains the node name of the backing file of + * reopen_state->bs then return 0. + * + * If 'backing' contains a different node name (or is null) then check + * whether the current backing file can be replaced with the new one. + * If that's the case then reopen_state->replace_backing_bs is set to + * true and reopen_state->new_backing_bs contains a pointer to the new + * backing BlockDriverState (or NULL). + * + * Return 0 on success, otherwise return < 0 and set @errp. + */ +static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state, + Error **errp) +{ + BlockDriverState *bs = reopen_state->bs; + BlockDriverState *overlay_bs, *new_backing_bs; + QObject *value; + const char *str; + + value = qdict_get(reopen_state->options, "backing"); + if (value == NULL) { + return 0; + } + + switch (qobject_type(value)) { + case QTYPE_QNULL: + new_backing_bs = NULL; + break; + case QTYPE_QSTRING: + str = qobject_get_try_str(value); + new_backing_bs = bdrv_lookup_bs(NULL, str, errp); + if (new_backing_bs == NULL) { + return -EINVAL; + } else if (bdrv_recurse_has_child(new_backing_bs, bs)) { + error_setg(errp, "Making '%s' a backing file of '%s' " + "would create a cycle", str, bs->node_name); + return -EINVAL; + } + break; + default: + /* 'backing' does not allow any other data type */ + g_assert_not_reached(); + } + + /* + * TODO: before removing the x- prefix from x-blockdev-reopen we + * should move the new backing file into the right AioContext + * instead of returning an error. + */ + if (new_backing_bs) { + if (bdrv_get_aio_context(new_backing_bs) != bdrv_get_aio_context(bs)) { + error_setg(errp, "Cannot use a new backing file " + "with a different AioContext"); + return -EINVAL; + } + } + + /* + * Find the "actual" backing file by skipping all links that point + * to an implicit node, if any (e.g. a commit filter node). + */ + overlay_bs = bs; + while (backing_bs(overlay_bs) && backing_bs(overlay_bs)->implicit) { + overlay_bs = backing_bs(overlay_bs); + } + + /* If we want to replace the backing file we need some extra checks */ + if (new_backing_bs != backing_bs(overlay_bs)) { + /* Check for implicit nodes between bs and its backing file */ + if (bs != overlay_bs) { + error_setg(errp, "Cannot change backing link if '%s' has " + "an implicit backing file", bs->node_name); + return -EPERM; + } + /* Check if the backing link that we want to replace is frozen */ + if (bdrv_is_backing_chain_frozen(overlay_bs, backing_bs(overlay_bs), + errp)) { + return -EPERM; + } + reopen_state->replace_backing_bs = true; + if (new_backing_bs) { + bdrv_ref(new_backing_bs); + reopen_state->new_backing_bs = new_backing_bs; + } + } + + return 0; +} + +/* * Prepares a BlockDriverState for reopen. All changes are staged in the * 'opaque' field of the BDRVReopenState, which is used and allocated by * the block driver layer .bdrv_reopen_prepare() @@ -3447,6 +3582,17 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, goto error; } + /* + * Allow changing the 'backing' option. The new value can be + * either a reference to an existing node (using its node name) + * or NULL to simply detach the current backing file. + */ + ret = bdrv_reopen_parse_backing(reopen_state, errp); + if (ret < 0) { + goto error; + } + qdict_del(reopen_state->options, "backing"); + /* Options that are not handled are only okay if they are unchanged * compared to the old state. It is expected that some options are only * used for the initial open, but not reopen (e.g. filename) */ @@ -3556,6 +3702,11 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state) bs->read_only = !(reopen_state->flags & BDRV_O_RDWR); bs->detect_zeroes = reopen_state->detect_zeroes; + if (reopen_state->replace_backing_bs) { + qdict_del(bs->explicit_options, "backing"); + qdict_del(bs->options, "backing"); + } + /* Remove child references from bs->options and bs->explicit_options. * Child options were already removed in bdrv_reopen_queue_child() */ QLIST_FOREACH(child, &bs->children, next) { @@ -3563,6 +3714,21 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state) qdict_del(bs->options, child->name); } + /* + * Change the backing file if a new one was specified. We do this + * after updating bs->options, so bdrv_refresh_filename() (called + * from bdrv_set_backing_hd()) has the new values. + */ + if (reopen_state->replace_backing_bs) { + BlockDriverState *old_backing_bs = backing_bs(bs); + assert(!old_backing_bs || !old_backing_bs->implicit); + /* Abort the permission update on the backing bs we're detaching */ + if (old_backing_bs) { + bdrv_abort_perm_update(old_backing_bs); + } + bdrv_set_backing_hd(bs, reopen_state->new_backing_bs, &error_abort); + } + bdrv_refresh_limits(bs, NULL); new_can_write = diff --git a/include/block/block.h b/include/block/block.h index fcc61a3a19..68a3efbb43 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -188,6 +188,8 @@ typedef struct BDRVReopenState { int flags; BlockdevDetectZeroesOptions detect_zeroes; bool backing_missing; + bool replace_backing_bs; /* new_backing_bs is ignored if this is false */ + BlockDriverState *new_backing_bs; /* If NULL then detach the current bs */ uint64_t perm, shared_perm; QDict *options; QDict *explicit_options; |