Minor performance improvement, but given that we have hash tables available, avoid iterating in the visited nodes list every time just to check if a node has been already visited.
The data structure is not actually a proper hash map, but an hash set, as we are just adding nodes and not key,value pairs. Suggested-by: Hanna Reitz <hre...@redhat.com> Signed-off-by: Emanuele Giuseppe Esposito <eespo...@redhat.com> --- block.c | 28 ++++++++++++++++------------ include/block/block-global-state.h | 2 +- include/block/block_int-common.h | 3 ++- 3 files changed, 19 insertions(+), 14 deletions(-) diff --git a/block.c b/block.c index c80e49009a..c02a628336 100644 --- a/block.c +++ b/block.c @@ -109,7 +109,7 @@ 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, + GHashTable *visited, Transaction *tran, Error **errp); /* If non-zero, use only whitelisted block drivers */ @@ -7444,14 +7444,15 @@ typedef struct BdrvStateSetAioContext { } BdrvStateSetAioContext; static bool bdrv_parent_change_aio_context(BdrvChild *c, AioContext *ctx, - GSList **visited, Transaction *tran, + GHashTable *visited, + Transaction *tran, Error **errp) { GLOBAL_STATE_CODE(); - if (g_slist_find(*visited, c)) { + if (g_hash_table_contains(visited, c)) { return true; } - *visited = g_slist_prepend(*visited, c); + g_hash_table_add(visited, c); /* * A BdrvChildClass that doesn't handle AioContext changes cannot @@ -7482,14 +7483,14 @@ bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx, } bool bdrv_child_change_aio_context(BdrvChild *c, AioContext *ctx, - GSList **visited, Transaction *tran, + GHashTable *visited, Transaction *tran, Error **errp) { GLOBAL_STATE_CODE(); - if (g_slist_find(*visited, c)) { + if (g_hash_table_contains(visited, c)) { return true; } - *visited = g_slist_prepend(*visited, c); + g_hash_table_add(visited, c); return bdrv_change_aio_context(c->bs, ctx, visited, tran, errp); } @@ -7561,7 +7562,7 @@ static TransactionActionDrv set_aio_context = { * responsible for freeing the list afterwards. */ static bool bdrv_change_aio_context(BlockDriverState *bs, AioContext *ctx, - GSList **visited, Transaction *tran, + GHashTable *visited, Transaction *tran, Error **errp) { BdrvChild *c; @@ -7646,16 +7647,19 @@ int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx, BdrvChild *ignore_child, Error **errp) { Transaction *tran; - GSList *visited; + GHashTable *visited; int ret; AioContext *old_context = bdrv_get_aio_context(bs); GLOBAL_STATE_CODE(); /* Recursion phase: go through all nodes of the graph */ 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); + visited = g_hash_table_new(NULL, NULL); + if (ignore_child) { + g_hash_table_add(visited, ignore_child); + } + ret = bdrv_change_aio_context(bs, ctx, visited, tran, errp); + g_hash_table_destroy(visited); /* Linear phase: go through all callbacks collected in the transaction */ diff --git a/include/block/block-global-state.h b/include/block/block-global-state.h index fdcb81a175..ceecf0aa8e 100644 --- a/include/block/block-global-state.h +++ b/include/block/block-global-state.h @@ -230,7 +230,7 @@ bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx, AioContext *bdrv_child_get_parent_aio_context(BdrvChild *c); bool bdrv_child_change_aio_context(BdrvChild *c, AioContext *ctx, - GSList **visited, Transaction *tran, + GHashTable *visited, Transaction *tran, Error **errp); int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx, BdrvChild *ignore_child, Error **errp); diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h index 43828cf74f..c639873487 100644 --- a/include/block/block_int-common.h +++ b/include/block/block_int-common.h @@ -897,7 +897,8 @@ struct BdrvChildClass { void (*set_aio_ctx)(BdrvChild *child, AioContext *ctx, GSList **ignore); bool (*change_aio_ctx)(BdrvChild *child, AioContext *ctx, - GSList **visited, Transaction *tran, Error **errp); + GHashTable *visited, Transaction *tran, + Error **errp); AioContext *(*get_parent_aio_context)(BdrvChild *child); -- 2.31.1