diff options
| -rw-r--r-- | block.c | 220 | ||||
| -rw-r--r-- | include/block/block-global-state.h | 6 | ||||
| -rw-r--r-- | include/block/block_int-common.h | 3 |
3 files changed, 228 insertions, 1 deletions
@@ -104,6 +104,10 @@ static void bdrv_reopen_abort(BDRVReopenState *reopen_state); static bool bdrv_backing_overridden(BlockDriverState *bs); +static bool bdrv_change_aio_context(BlockDriverState *bs, AioContext *ctx, + GSList **visited, Transaction *tran, + Error **errp); + /* If non-zero, use only whitelisted block drivers */ static int use_bdrv_whitelist; @@ -7196,7 +7200,7 @@ static void bdrv_attach_aio_context(BlockDriverState *bs, * must not own the AioContext lock for new_context (unless new_context is the * same as the current context of bs). * - * @ignore will accumulate all visited BdrvChild object. The caller is + * @ignore will accumulate all visited BdrvChild objects. The caller is * responsible for freeing the list afterwards. */ void bdrv_set_aio_context_ignore(BlockDriverState *bs, @@ -7305,6 +7309,38 @@ static bool bdrv_parent_can_set_aio_context(BdrvChild *c, AioContext *ctx, return true; } +typedef struct BdrvStateSetAioContext { + AioContext *new_ctx; + BlockDriverState *bs; +} BdrvStateSetAioContext; + +static bool bdrv_parent_change_aio_context(BdrvChild *c, AioContext *ctx, + GSList **visited, Transaction *tran, + Error **errp) +{ + GLOBAL_STATE_CODE(); + if (g_slist_find(*visited, c)) { + return true; + } + *visited = g_slist_prepend(*visited, c); + + /* + * A BdrvChildClass that doesn't handle AioContext changes cannot + * tolerate any AioContext changes + */ + if (!c->klass->change_aio_ctx) { + char *user = bdrv_child_user_desc(c); + error_setg(errp, "Changing iothreads is not supported by %s", user); + g_free(user); + return false; + } + if (!c->klass->change_aio_ctx(c, ctx, visited, tran, errp)) { + assert(!errp || *errp); + return false; + } + return true; +} + bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx, GSList **ignore, Error **errp) { @@ -7316,6 +7352,18 @@ bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx, return bdrv_can_set_aio_context(c->bs, ctx, ignore, errp); } +bool bdrv_child_change_aio_context(BdrvChild *c, AioContext *ctx, + GSList **visited, Transaction *tran, + Error **errp) +{ + GLOBAL_STATE_CODE(); + if (g_slist_find(*visited, c)) { + return true; + } + *visited = g_slist_prepend(*visited, c); + return bdrv_change_aio_context(c->bs, ctx, visited, tran, errp); +} + /* @ignore will accumulate all visited BdrvChild object. The caller is * responsible for freeing the list afterwards. */ bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx, @@ -7343,6 +7391,98 @@ bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx, return true; } +static void bdrv_set_aio_context_clean(void *opaque) +{ + BdrvStateSetAioContext *state = (BdrvStateSetAioContext *) opaque; + BlockDriverState *bs = (BlockDriverState *) state->bs; + + /* Paired with bdrv_drained_begin in bdrv_change_aio_context() */ + bdrv_drained_end(bs); + + g_free(state); +} + +static void bdrv_set_aio_context_commit(void *opaque) +{ + BdrvStateSetAioContext *state = (BdrvStateSetAioContext *) opaque; + BlockDriverState *bs = (BlockDriverState *) state->bs; + AioContext *new_context = state->new_ctx; + AioContext *old_context = bdrv_get_aio_context(bs); + assert_bdrv_graph_writable(bs); + + /* + * Take the old AioContex when detaching it from bs. + * At this point, new_context lock is already acquired, and we are now + * also taking old_context. This is safe as long as bdrv_detach_aio_context + * does not call AIO_POLL_WHILE(). + */ + if (old_context != qemu_get_aio_context()) { + aio_context_acquire(old_context); + } + bdrv_detach_aio_context(bs); + if (old_context != qemu_get_aio_context()) { + aio_context_release(old_context); + } + bdrv_attach_aio_context(bs, new_context); +} + +static TransactionActionDrv set_aio_context = { + .commit = bdrv_set_aio_context_commit, + .clean = bdrv_set_aio_context_clean, +}; + +/* + * Changes the AioContext used for fd handlers, timers, and BHs by this + * BlockDriverState and all its children and parents. + * + * Must be called from the main AioContext. + * + * The caller must own the AioContext lock for the old AioContext of bs, but it + * must not own the AioContext lock for new_context (unless new_context is the + * same as the current context of bs). + * + * @visited will accumulate all visited BdrvChild objects. The caller is + * responsible for freeing the list afterwards. + */ +static bool bdrv_change_aio_context(BlockDriverState *bs, AioContext *ctx, + GSList **visited, Transaction *tran, + Error **errp) +{ + BdrvChild *c; + BdrvStateSetAioContext *state; + + GLOBAL_STATE_CODE(); + + if (bdrv_get_aio_context(bs) == ctx) { + return true; + } + + QLIST_FOREACH(c, &bs->parents, next_parent) { + if (!bdrv_parent_change_aio_context(c, ctx, visited, tran, errp)) { + return false; + } + } + + QLIST_FOREACH(c, &bs->children, next) { + if (!bdrv_child_change_aio_context(c, ctx, visited, tran, errp)) { + return false; + } + } + + state = g_new(BdrvStateSetAioContext, 1); + *state = (BdrvStateSetAioContext) { + .new_ctx = ctx, + .bs = bs, + }; + + /* Paired with bdrv_drained_end in bdrv_set_aio_context_clean() */ + bdrv_drained_begin(bs); + + tran_add(tran, &set_aio_context, state); + + return true; +} + int bdrv_child_try_set_aio_context(BlockDriverState *bs, AioContext *ctx, BdrvChild *ignore_child, Error **errp) { @@ -7366,6 +7506,84 @@ int bdrv_child_try_set_aio_context(BlockDriverState *bs, AioContext *ctx, return 0; } +/* + * Change bs's and recursively all of its parents' and children's AioContext + * to the given new context, returning an error if that isn't possible. + * + * If ignore_child is not NULL, that child (and its subgraph) will not + * be touched. + * + * This function still requires the caller to take the bs current + * AioContext lock, otherwise draining will fail since AIO_WAIT_WHILE + * assumes the lock is always held if bs is in another AioContext. + * For the same reason, it temporarily also holds the new AioContext, since + * bdrv_drained_end calls BDRV_POLL_WHILE that assumes the lock is taken too. + * Therefore the new AioContext lock must not be taken by the caller. + */ +int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx, + BdrvChild *ignore_child, Error **errp) +{ + Transaction *tran; + GSList *visited; + int ret; + AioContext *old_context = bdrv_get_aio_context(bs); + GLOBAL_STATE_CODE(); + + /* + * Recursion phase: go through all nodes of the graph. + * Take care of checking that all nodes support changing AioContext + * and drain them, builing a linear list of callbacks to run if everything + * is successful (the transaction itself). + */ + tran = tran_new(); + visited = ignore_child ? g_slist_prepend(NULL, ignore_child) : NULL; + ret = bdrv_change_aio_context(bs, ctx, &visited, tran, errp); + g_slist_free(visited); + + /* + * Linear phase: go through all callbacks collected in the transaction. + * Run all callbacks collected in the recursion to switch all nodes + * AioContext lock (transaction commit), or undo all changes done in the + * recursion (transaction abort). + */ + + if (!ret) { + /* Just run clean() callbacks. No AioContext changed. */ + tran_abort(tran); + return -EPERM; + } + + /* + * Release old AioContext, it won't be needed anymore, as all + * bdrv_drained_begin() have been called already. + */ + if (qemu_get_aio_context() != old_context) { + aio_context_release(old_context); + } + + /* + * Acquire new AioContext since bdrv_drained_end() is going to be called + * after we switched all nodes in the new AioContext, and the function + * assumes that the lock of the bs is always taken. + */ + if (qemu_get_aio_context() != ctx) { + aio_context_acquire(ctx); + } + + tran_commit(tran); + + if (qemu_get_aio_context() != ctx) { + aio_context_release(ctx); + } + + /* Re-acquire the old AioContext, since the caller takes and releases it. */ + if (qemu_get_aio_context() != old_context) { + aio_context_acquire(old_context); + } + + return 0; +} + int bdrv_try_set_aio_context(BlockDriverState *bs, AioContext *ctx, Error **errp) { diff --git a/include/block/block-global-state.h b/include/block/block-global-state.h index 29a38d7..7b0095b 100644 --- a/include/block/block-global-state.h +++ b/include/block/block-global-state.h @@ -232,6 +232,12 @@ bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx, GSList **ignore, Error **errp); AioContext *bdrv_child_get_parent_aio_context(BdrvChild *c); +bool bdrv_child_change_aio_context(BdrvChild *c, AioContext *ctx, + GSList **visited, Transaction *tran, + Error **errp); +int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx, + BdrvChild *ignore_child, Error **errp); + int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz); int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo); diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h index 1f300ee..9067a99 100644 --- a/include/block/block_int-common.h +++ b/include/block/block_int-common.h @@ -910,6 +910,9 @@ struct BdrvChildClass { GSList **ignore, Error **errp); void (*set_aio_ctx)(BdrvChild *child, AioContext *ctx, GSList **ignore); + bool (*change_aio_ctx)(BdrvChild *child, AioContext *ctx, + GSList **visited, Transaction *tran, Error **errp); + AioContext *(*get_parent_aio_context)(BdrvChild *child); /* |