On Sat, Aug 15, 2026 at 01:48:19AM +0800, Zhang Chen wrote: > Track the IOThreads used by a block export and identify the holder > with the unique BlockExportOptions id. > > Acquire holder-aware references during export creation and release > them on error or export deletion. Support both single- and > multi-iothread exports. > > Signed-off-by: Zhang Chen <[email protected]> > --- > block/export/export.c | 79 +++++++++++++++++++++++++++++++++++++----- > include/block/export.h | 6 ++++ > 2 files changed, 76 insertions(+), 9 deletions(-) > > diff --git a/block/export/export.c b/block/export/export.c > index b733f269f3..09136cda34 100644 > --- a/block/export/export.c > +++ b/block/export/export.c > @@ -15,7 +15,6 @@ > > #include "block/block.h" > #include "system/block-backend.h" > -#include "system/iothread.h" > #include "block/export.h" > #include "block/fuse.h" > #include "block/nbd.h" > @@ -85,6 +84,8 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error > **errp) > AioContext *ctx; > AioContext **multithread_ctxs = NULL; > size_t multithread_count = 0; > + g_autofree IOThread **local_iothreads = NULL; > + char *holder_id = NULL; > uint64_t perm; > int ret; > > @@ -139,7 +140,16 @@ BlockExport *blk_exp_add(BlockExportOptions *export, > Error **errp) > goto fail; > } > > - new_ctx = iothread_get_aio_context(iothread); > + holder_id = export->id; > + const IOThreadHolder holder = { > + .type = IO_THREAD_HOLDER_KIND_BLOCK_EXPORT, > + .u.block_export.export_id = holder_id, > + }; > + > + new_ctx = iothread_ref_and_get_aio_context(iothread, &holder); > + multithread_count = 1; > + local_iothreads = g_new0(IOThread *, 1); > + local_iothreads[0] = iothread; > > /* Ignore errors with fixed-iothread=false */ > set_context_errp = fixed_iothread ? errp : NULL; > @@ -163,8 +173,15 @@ BlockExport *blk_exp_add(BlockExportOptions *export, > Error **errp) > return NULL; > } > > + local_iothreads = g_new0(IOThread *, multithread_count); > multithread_ctxs = g_new(AioContext *, multithread_count); > i = 0; > + holder_id = export->id; > + const IOThreadHolder holder = { > + .type = IO_THREAD_HOLDER_KIND_BLOCK_EXPORT, > + .u.block_export.export_id = holder_id, > + }; > + > for (strList *e = iothread_list; e; e = e->next) { > IOThread *iothread = iothread_by_id(e->value); > > @@ -172,7 +189,9 @@ BlockExport *blk_exp_add(BlockExportOptions *export, > Error **errp) > error_setg(errp, "iothread \"%s\" not found", e->value); > goto fail; > } > - multithread_ctxs[i++] = iothread_get_aio_context(iothread); > + local_iothreads[i] = iothread; > + multithread_ctxs[i++] = > iothread_ref_and_get_aio_context(iothread, > + > &holder); > } > assert(i == multithread_count); > } > @@ -225,12 +244,15 @@ BlockExport *blk_exp_add(BlockExportOptions *export, > Error **errp) > assert(drv->instance_size >= sizeof(BlockExport)); > exp = g_malloc0(drv->instance_size); > *exp = (BlockExport) { > - .drv = drv, > - .refcount = 1, > - .user_owned = true, > - .id = g_strdup(export->id), > - .ctx = ctx, > - .blk = blk, > + .drv = drv, > + .refcount = 1, > + .user_owned = true, > + .id = g_strdup(export->id), > + .ctx = ctx, > + .blk = blk, > + .iothreads = g_steal_pointer(&local_iothreads), > + .iothread_count = multithread_count, > + .iothread_holder_id = g_strdup(holder_id),
Is this field necessary, it always seems to be the same as exp->id?
> };
>
> ret = drv->create(exp, export, multithread_ctxs, multithread_count,
> errp);
> @@ -250,8 +272,33 @@ fail:
> blk_unref(blk);
> }
> if (exp) {
> + if (exp->iothreads) {
> + const IOThreadHolder holder = {
> + .type = IO_THREAD_HOLDER_KIND_BLOCK_EXPORT,
> + .u.block_export.export_id = exp->iothread_holder_id,
> + };
> + for (size_t j = 0; j < exp->iothread_count; j++) {
> + if (exp->iothreads[j]) {
> + iothread_unref_and_put_aio_context(exp->iothreads[j],
> + &holder);
> + }
> + }
> + g_free(exp->iothreads);
> + }
> + g_free(exp->iothread_holder_id);
> g_free(exp->id);
> g_free(exp);
> + } else if (local_iothreads) {
> + const IOThreadHolder holder = {
> + .type = IO_THREAD_HOLDER_KIND_BLOCK_EXPORT,
> + .u.block_export.export_id = holder_id,
> + };
> +
> + for (size_t j = 0; j < multithread_count; j++) {
> + if (local_iothreads[j]) {
> + iothread_unref_and_put_aio_context(local_iothreads[j],
> &holder);
> + }
> + }
> }
> g_free(multithread_ctxs);
> return NULL;
> @@ -273,6 +320,20 @@ static void blk_exp_delete_bh(void *opaque)
> exp->drv->delete(exp);
> blk_set_dev_ops(exp->blk, NULL, NULL);
> blk_unref(exp->blk);
> +
> + if (exp->iothreads) {
> + const IOThreadHolder holder = {
> + .type = IO_THREAD_HOLDER_KIND_BLOCK_EXPORT,
> + .u.block_export.export_id = exp->iothread_holder_id,
> + };
> +
> + for (size_t i = 0; i < exp->iothread_count; i++) {
> + iothread_unref_and_put_aio_context(exp->iothreads[i], &holder);
> + }
> + g_free(exp->iothreads);
> + }
> +
> + g_free(exp->iothread_holder_id);
> qapi_event_send_block_export_deleted(exp->id);
> g_free(exp->id);
> g_free(exp);
There is quite a bit of code duplication with the loops that call
iothread_ref_and_get_aio_context() or
iothread_unref_and_put_aio_context().
Two helper functions could avoid duplication:
static void init_iothreads(const char *holder_id,
IOThread **iothreads,
size_t num_iothreads,
AioContext **aio_ctxs);
static void cleanup_iothreads(const char *holder_id,
IOThread **iothreads,
size_t num_iothreads);
> diff --git a/include/block/export.h b/include/block/export.h
> index ca45da928c..a093dea0b6 100644
> --- a/include/block/export.h
> +++ b/include/block/export.h
> @@ -16,6 +16,7 @@
>
> #include "qapi/qapi-types-block-export.h"
> #include "qemu/queue.h"
> +#include "system/iothread.h"
>
> typedef struct BlockExport BlockExport;
>
> @@ -89,6 +90,11 @@ struct BlockExport {
>
> /* List entry for block_exports */
> QLIST_ENTRY(BlockExport) next;
> +
> + /* The IOThreads utilized by this specific block export */
> + IOThread **iothreads;
> + size_t iothread_count;
> + char *iothread_holder_id;
> };
>
> BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp);
> --
> 2.54.0
>
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