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GET /api/patches/2197742/?format=api
{ "id": 2197742, "url": "http://patchwork.ozlabs.org/api/patches/2197742/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260218132633.29748-20-hreitz@redhat.com/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/projects/14/?format=api", "name": "QEMU Development", "link_name": "qemu-devel", "list_id": "qemu-devel.nongnu.org", "list_email": "qemu-devel@nongnu.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260218132633.29748-20-hreitz@redhat.com>", "list_archive_url": null, "date": "2026-02-18T13:26:28", "name": "[v4,19/24] block/export: Add multi-threading interface", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "f48ad47ad4a30da377382856e8b3a2879cd904d2", "submitter": { "id": 82279, "url": "http://patchwork.ozlabs.org/api/people/82279/?format=api", "name": "Hanna Czenczek", "email": "hreitz@redhat.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/patch/20260218132633.29748-20-hreitz@redhat.com/mbox/", "series": [ { "id": 492547, "url": "http://patchwork.ozlabs.org/api/series/492547/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=492547", "date": "2026-02-18T13:26:09", "name": "export/fuse: Use coroutines and multi-threading", "version": 4, "mbox": "http://patchwork.ozlabs.org/series/492547/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2197742/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2197742/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=bqb5Hx3I;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=google header.b=Kz8lGsjc;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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charset=UTF-8", "Content-Transfer-Encoding": "8bit", "Received-SPF": "pass client-ip=170.10.133.124; envelope-from=hreitz@redhat.com;\n helo=us-smtp-delivery-124.mimecast.com", "X-Spam_score_int": "-20", "X-Spam_score": "-2.1", "X-Spam_bar": "--", "X-Spam_report": "(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.043,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n SPF_HELO_PASS=-0.001,\n SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no", "X-Spam_action": "no action", "X-BeenThere": "qemu-devel@nongnu.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "qemu development <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "Errors-To": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org", "Sender": "qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org" }, "content": "Make BlockExportType.iothread an alternate between a single-thread\nvariant 'str' and a multi-threading variant '[str]'.\n\nIn contrast to the single-thread setting, the multi-threading setting\nwill not change the BDS's context (and so is incompatible with the\nfixed-iothread setting), but instead just pass a list to the export\ndriver, with which it can do whatever it wants.\n\nCurrently no export driver supports multi-threading, so they all return\nan error when receiving such a list.\n\nSuggested-by: Kevin Wolf <kwolf@redhat.com>\nAcked-by: Markus Armbruster <armbru@redhat.com>\nReviewed-by: Stefan Hajnoczi <stefanha@redhat.com>\nSigned-off-by: Hanna Czenczek <hreitz@redhat.com>\n---\n qapi/block-export.json | 36 ++++++++++++++++++---\n include/block/export.h | 12 +++++--\n block/export/export.c | 48 +++++++++++++++++++++++++---\n block/export/fuse.c | 7 ++++\n block/export/vduse-blk.c | 7 ++++\n block/export/vhost-user-blk-server.c | 8 +++++\n nbd/server.c | 6 ++++\n 7 files changed, 113 insertions(+), 11 deletions(-)", "diff": "diff --git a/qapi/block-export.json b/qapi/block-export.json\nindex 076954ef1a..160cd2e3ca 100644\n--- a/qapi/block-export.json\n+++ b/qapi/block-export.json\n@@ -363,14 +363,16 @@\n # to the export before completion is signalled. (since: 5.2;\n # default: false)\n #\n-# @iothread: The name of the iothread object where the export will\n-# run. The default is to use the thread currently associated with\n-# the block node. (since: 5.2)\n+# @iothread: The name(s) of one or more iothread object(s) where the\n+# export will run. The default is to use the thread currently\n+# associated with the block node. (since: 5.2; multi-threading\n+# since 10.1)\n #\n # @fixed-iothread: True prevents the block node from being moved to\n # another thread while the export is active. If true and\n # @iothread is given, export creation fails if the block node\n-# cannot be moved to the iothread. The default is false.\n+# cannot be moved to the iothread. Must not be true when giving\n+# multiple iothreads for @iothread. The default is false.\n # (since: 5.2)\n #\n # @allow-inactive: If true, the export allows the exported node to be\n@@ -387,7 +389,7 @@\n 'base': { 'type': 'BlockExportType',\n 'id': 'str',\n '*fixed-iothread': 'bool',\n- '*iothread': 'str',\n+ '*iothread': 'BlockExportIothreads',\n 'node-name': 'str',\n '*writable': 'bool',\n '*writethrough': 'bool',\n@@ -403,6 +405,30 @@\n 'if': 'CONFIG_VDUSE_BLK_EXPORT' }\n } }\n \n+##\n+# @BlockExportIothreads:\n+#\n+# Specify a single or multiple I/O threads in which to run a block\n+# export's I/O.\n+#\n+# @single: Run the export's I/O in the given single I/O thread.\n+#\n+# @multi: Use multi-threading across the given set of I/O threads,\n+# which must not be empty. Note: Passing a single I/O thread via\n+# this variant is still treated as multi-threading, which is\n+# different from using the @single variant. In particular, even\n+# if there only is a single I/O thread in the set, export types\n+# that do not support multi-threading will generally reject this\n+# variant, and BlockExportOptions.fixed-iothread is always\n+# incompatible with it.\n+#\n+# Since: 10.1\n+##\n+{ 'alternate': 'BlockExportIothreads',\n+ 'data': {\n+ 'single': 'str',\n+ 'multi': ['str'] } }\n+\n ##\n # @block-export-add:\n #\ndiff --git a/include/block/export.h b/include/block/export.h\nindex 4bd9531d4d..ca45da928c 100644\n--- a/include/block/export.h\n+++ b/include/block/export.h\n@@ -32,8 +32,16 @@ typedef struct BlockExportDriver {\n /* True if the export type supports running on an inactive node */\n bool supports_inactive;\n \n- /* Creates and starts a new block export */\n- int (*create)(BlockExport *, BlockExportOptions *, Error **);\n+ /*\n+ * Creates and starts a new block export.\n+ *\n+ * If the user passed a set of I/O threads for multi-threading, @multithread\n+ * is a list of the @multithread_count corresponding contexts (freed by the\n+ * caller). Note that @exp->ctx has no relation to that list.\n+ */\n+ int (*create)(BlockExport *exp, BlockExportOptions *opts,\n+ AioContext *const *multithread, size_t multithread_count,\n+ Error **errp);\n \n /*\n * Frees a removed block export. This function is only called after all\ndiff --git a/block/export/export.c b/block/export/export.c\nindex f3bbf11070..b733f269f3 100644\n--- a/block/export/export.c\n+++ b/block/export/export.c\n@@ -76,16 +76,26 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)\n {\n bool fixed_iothread = export->has_fixed_iothread && export->fixed_iothread;\n bool allow_inactive = export->has_allow_inactive && export->allow_inactive;\n+ bool multithread = export->iothread &&\n+ export->iothread->type == QTYPE_QLIST;\n const BlockExportDriver *drv;\n BlockExport *exp = NULL;\n BlockDriverState *bs;\n BlockBackend *blk = NULL;\n AioContext *ctx;\n+ AioContext **multithread_ctxs = NULL;\n+ size_t multithread_count = 0;\n uint64_t perm;\n int ret;\n \n GLOBAL_STATE_CODE();\n \n+ if (fixed_iothread && multithread) {\n+ error_setg(errp,\n+ \"Cannot use fixed-iothread for a multi-threaded export\");\n+ return NULL;\n+ }\n+\n if (!id_wellformed(export->id)) {\n error_setg(errp, \"Invalid block export id\");\n return NULL;\n@@ -116,14 +126,16 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)\n \n ctx = bdrv_get_aio_context(bs);\n \n- if (export->iothread) {\n+ /* Move the BDS to the target I/O thread, if it is a single one */\n+ if (export->iothread && !multithread) {\n+ const char *iothread_id = export->iothread->u.single;\n IOThread *iothread;\n AioContext *new_ctx;\n Error **set_context_errp;\n \n- iothread = iothread_by_id(export->iothread);\n+ iothread = iothread_by_id(iothread_id);\n if (!iothread) {\n- error_setg(errp, \"iothread \\\"%s\\\" not found\", export->iothread);\n+ error_setg(errp, \"iothread \\\"%s\\\" not found\", iothread_id);\n goto fail;\n }\n \n@@ -137,6 +149,32 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)\n } else if (fixed_iothread) {\n goto fail;\n }\n+ } else if (multithread) {\n+ strList *iothread_list = export->iothread->u.multi;\n+ size_t i;\n+\n+ multithread_count = 0;\n+ for (strList *e = iothread_list; e; e = e->next) {\n+ multithread_count++;\n+ }\n+\n+ if (multithread_count == 0) {\n+ error_setg(errp, \"The set of I/O threads must not be empty\");\n+ return NULL;\n+ }\n+\n+ multithread_ctxs = g_new(AioContext *, multithread_count);\n+ i = 0;\n+ for (strList *e = iothread_list; e; e = e->next) {\n+ IOThread *iothread = iothread_by_id(e->value);\n+\n+ if (!iothread) {\n+ error_setg(errp, \"iothread \\\"%s\\\" not found\", e->value);\n+ goto fail;\n+ }\n+ multithread_ctxs[i++] = iothread_get_aio_context(iothread);\n+ }\n+ assert(i == multithread_count);\n }\n \n bdrv_graph_rdlock_main_loop();\n@@ -195,7 +233,7 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)\n .blk = blk,\n };\n \n- ret = drv->create(exp, export, errp);\n+ ret = drv->create(exp, export, multithread_ctxs, multithread_count, errp);\n if (ret < 0) {\n goto fail;\n }\n@@ -203,6 +241,7 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)\n assert(exp->blk != NULL);\n \n QLIST_INSERT_HEAD(&block_exports, exp, next);\n+ g_free(multithread_ctxs);\n return exp;\n \n fail:\n@@ -214,6 +253,7 @@ fail:\n g_free(exp->id);\n g_free(exp);\n }\n+ g_free(multithread_ctxs);\n return NULL;\n }\n \ndiff --git a/block/export/fuse.c b/block/export/fuse.c\nindex b60affe86b..aa4f1c0307 100644\n--- a/block/export/fuse.c\n+++ b/block/export/fuse.c\n@@ -260,6 +260,8 @@ static const BlockDevOps fuse_export_blk_dev_ops = {\n \n static int fuse_export_create(BlockExport *blk_exp,\n BlockExportOptions *blk_exp_args,\n+ AioContext *const *multithread,\n+ size_t mt_count,\n Error **errp)\n {\n ERRP_GUARD(); /* ensure clean-up even with error_fatal */\n@@ -269,6 +271,11 @@ static int fuse_export_create(BlockExport *blk_exp,\n \n assert(blk_exp_args->type == BLOCK_EXPORT_TYPE_FUSE);\n \n+ if (multithread) {\n+ error_setg(errp, \"FUSE export does not support multi-threading\");\n+ return -EINVAL;\n+ }\n+\n /* For growable and writable exports, take the RESIZE permission */\n if (args->growable || blk_exp_args->writable) {\n uint64_t blk_perm, blk_shared_perm;\ndiff --git a/block/export/vduse-blk.c b/block/export/vduse-blk.c\nindex 8af13b7f0b..10dc673c56 100644\n--- a/block/export/vduse-blk.c\n+++ b/block/export/vduse-blk.c\n@@ -267,6 +267,7 @@ static const BlockDevOps vduse_block_ops = {\n };\n \n static int vduse_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,\n+ AioContext *const *multithread, size_t mt_count,\n Error **errp)\n {\n VduseBlkExport *vblk_exp = container_of(exp, VduseBlkExport, export);\n@@ -302,6 +303,12 @@ static int vduse_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,\n return -EINVAL;\n }\n }\n+\n+ if (multithread) {\n+ error_setg(errp, \"vduse-blk export does not support multi-threading\");\n+ return -EINVAL;\n+ }\n+\n vblk_exp->num_queues = num_queues;\n vblk_exp->handler.blk = exp->blk;\n vblk_exp->handler.serial = g_strdup(vblk_opts->serial ?: \"\");\ndiff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c\nindex a4d54e824f..e89422bb85 100644\n--- a/block/export/vhost-user-blk-server.c\n+++ b/block/export/vhost-user-blk-server.c\n@@ -316,6 +316,7 @@ static const BlockDevOps vu_blk_dev_ops = {\n };\n \n static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,\n+ AioContext *const *multithread, size_t mt_count,\n Error **errp)\n {\n VuBlkExport *vexp = container_of(exp, VuBlkExport, export);\n@@ -341,6 +342,13 @@ static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,\n error_setg(errp, \"num-queues must be greater than 0\");\n return -EINVAL;\n }\n+\n+ if (multithread) {\n+ error_setg(errp,\n+ \"vhost-user-blk export does not support multi-threading\");\n+ return -EINVAL;\n+ }\n+\n vexp->handler.blk = exp->blk;\n vexp->handler.serial = g_strdup(\"vhost_user_blk\");\n vexp->handler.logical_block_size = logical_block_size;\ndiff --git a/nbd/server.c b/nbd/server.c\nindex acec0487a8..620097c58c 100644\n--- a/nbd/server.c\n+++ b/nbd/server.c\n@@ -1795,6 +1795,7 @@ static const BlockDevOps nbd_block_ops = {\n };\n \n static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,\n+ AioContext *const *multithread, size_t mt_count,\n Error **errp)\n {\n NBDExport *exp = container_of(blk_exp, NBDExport, common);\n@@ -1831,6 +1832,11 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,\n return -EEXIST;\n }\n \n+ if (multithread) {\n+ error_setg(errp, \"NBD export does not support multi-threading\");\n+ return -EINVAL;\n+ }\n+\n size = blk_getlength(blk);\n if (size < 0) {\n error_setg_errno(errp, -size,\n", "prefixes": [ "v4", "19/24" ] }