block/export/export.c - qemu - Git at Google

 /*
  * Common block export infrastructure
  *
  * Copyright (c) 2012, 2020 Red Hat, Inc.
  *
  * Authors:
  * Paolo Bonzini <pbonzini@redhat.com>
  * Kevin Wolf <kwolf@redhat.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or
  * later.  See the COPYING file in the top-level directory.
  */

 #include "qemu/osdep.h"

 #include "block/block.h"
 #include "sysemu/block-backend.h"
 #include "sysemu/iothread.h"
 #include "block/export.h"
 #include "block/fuse.h"
 #include "block/nbd.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-block-export.h"
 #include "qapi/qapi-events-block-export.h"
 #include "qemu/id.h"
 #ifdef CONFIG_VHOST_USER_BLK_SERVER
 #include "vhost-user-blk-server.h"
 #endif
 #ifdef CONFIG_VDUSE_BLK_EXPORT
 #include "vduse-blk.h"
 #endif

 static const BlockExportDriver *blk_exp_drivers[] = {
     &blk_exp_nbd,
 #ifdef CONFIG_VHOST_USER_BLK_SERVER
     &blk_exp_vhost_user_blk,
 #endif
 #ifdef CONFIG_FUSE
     &blk_exp_fuse,
 #endif
 #ifdef CONFIG_VDUSE_BLK_EXPORT
     &blk_exp_vduse_blk,
 #endif
 };

 /* Only accessed from the main thread */
 static QLIST_HEAD(, BlockExport) block_exports =
     QLIST_HEAD_INITIALIZER(block_exports);

 BlockExport *blk_exp_find(const char *id)
 {
     BlockExport *exp;

     QLIST_FOREACH(exp, &block_exports, next) {
         if (strcmp(id, exp->id) == 0) {
             return exp;
         }
     }

     return NULL;
 }

 static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
 {
     int i;

     for (i = 0; i < ARRAY_SIZE(blk_exp_drivers); i++) {
         if (blk_exp_drivers[i]->type == type) {
             return blk_exp_drivers[i];
         }
     }
     return NULL;
 }

 BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
 {
     bool fixed_iothread = export->has_fixed_iothread && export->fixed_iothread;
     const BlockExportDriver *drv;
     BlockExport *exp = NULL;
     BlockDriverState *bs;
     BlockBackend *blk = NULL;
     AioContext *ctx;
     uint64_t perm;
     int ret;

     if (!id_wellformed(export->id)) {
         error_setg(errp, "Invalid block export id");
         return NULL;
     }
     if (blk_exp_find(export->id)) {
         error_setg(errp, "Block export id '%s' is already in use", export->id);
         return NULL;
     }

     drv = blk_exp_find_driver(export->type);
     if (!drv) {
         error_setg(errp, "No driver found for the requested export type");
         return NULL;
     }

     bs = bdrv_lookup_bs(NULL, export->node_name, errp);
     if (!bs) {
         return NULL;
     }

     if (!export->has_writable) {
         export->writable = false;
     }
     if (bdrv_is_read_only(bs) && export->writable) {
         error_setg(errp, "Cannot export read-only node as writable");
         return NULL;
     }

     ctx = bdrv_get_aio_context(bs);
     aio_context_acquire(ctx);

     if (export->iothread) {
         IOThread *iothread;
         AioContext *new_ctx;
         Error **set_context_errp;

         iothread = iothread_by_id(export->iothread);
         if (!iothread) {
             error_setg(errp, "iothread \"%s\" not found", export->iothread);
             goto fail;
         }

         new_ctx = iothread_get_aio_context(iothread);

         /* Ignore errors with fixed-iothread=false */
         set_context_errp = fixed_iothread ? errp : NULL;
         ret = bdrv_try_change_aio_context(bs, new_ctx, NULL, set_context_errp);
         if (ret == 0) {
             aio_context_release(ctx);
             aio_context_acquire(new_ctx);
             ctx = new_ctx;
         } else if (fixed_iothread) {
             goto fail;
         }
     }

     /*
      * Block exports are used for non-shared storage migration. Make sure
      * that BDRV_O_INACTIVE is cleared and the image is ready for write
      * access since the export could be available before migration handover.
      * ctx was acquired in the caller.
      */
     bdrv_activate(bs, NULL);

     perm = BLK_PERM_CONSISTENT_READ;
     if (export->writable) {
         perm |= BLK_PERM_WRITE;
     }

     blk = blk_new(ctx, perm, BLK_PERM_ALL);

     if (!fixed_iothread) {
         blk_set_allow_aio_context_change(blk, true);
     }

     ret = blk_insert_bs(blk, bs, errp);
     if (ret < 0) {
         goto fail;
     }

     if (!export->has_writethrough) {
         export->writethrough = false;
     }
     blk_set_enable_write_cache(blk, !export->writethrough);

     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,
     };

     ret = drv->create(exp, export, errp);
     if (ret < 0) {
         goto fail;
     }

     assert(exp->blk != NULL);

     QLIST_INSERT_HEAD(&block_exports, exp, next);

     aio_context_release(ctx);
     return exp;

 fail:
     if (blk) {
         blk_set_dev_ops(blk, NULL, NULL);
         blk_unref(blk);
     }
     aio_context_release(ctx);
     if (exp) {
         g_free(exp->id);
         g_free(exp);
     }
     return NULL;
 }

 /* Callers must hold exp->ctx lock */
 void blk_exp_ref(BlockExport *exp)
 {
     assert(exp->refcount > 0);
     exp->refcount++;
 }

 /* Runs in the main thread */
 static void blk_exp_delete_bh(void *opaque)
 {
     BlockExport *exp = opaque;
     AioContext *aio_context = exp->ctx;

     aio_context_acquire(aio_context);

     assert(exp->refcount == 0);
     QLIST_REMOVE(exp, next);
     exp->drv->delete(exp);
     blk_set_dev_ops(exp->blk, NULL, NULL);
     blk_unref(exp->blk);
     qapi_event_send_block_export_deleted(exp->id);
     g_free(exp->id);
     g_free(exp);

     aio_context_release(aio_context);
 }

 /* Callers must hold exp->ctx lock */
 void blk_exp_unref(BlockExport *exp)
 {
     assert(exp->refcount > 0);
     if (--exp->refcount == 0) {
         /* Touch the block_exports list only in the main thread */
         aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh,
                                 exp);
     }
 }

 /*
  * Drops the user reference to the export and requests that all client
  * connections and other internally held references start to shut down. When
  * the function returns, there may still be active references while the export
  * is in the process of shutting down.
  *
  * Acquires exp->ctx internally. Callers must *not* hold the lock.
  */
 void blk_exp_request_shutdown(BlockExport *exp)
 {
     AioContext *aio_context = exp->ctx;

     aio_context_acquire(aio_context);

     /*
      * If the user doesn't own the export any more, it is already shutting
      * down. We must not call .request_shutdown and decrease the refcount a
      * second time.
      */
     if (!exp->user_owned) {
         goto out;
     }

     exp->drv->request_shutdown(exp);

     assert(exp->user_owned);
     exp->user_owned = false;
     blk_exp_unref(exp);

 out:
     aio_context_release(aio_context);
 }

 /*
  * Returns whether a block export of the given type exists.
  * type == BLOCK_EXPORT_TYPE__MAX checks for an export of any type.
  */
 static bool blk_exp_has_type(BlockExportType type)
 {
     BlockExport *exp;

     if (type == BLOCK_EXPORT_TYPE__MAX) {
         return !QLIST_EMPTY(&block_exports);
     }

     QLIST_FOREACH(exp, &block_exports, next) {
         if (exp->drv->type == type) {
             return true;
         }
     }

     return false;
 }

 /* type == BLOCK_EXPORT_TYPE__MAX for all types */
 void blk_exp_close_all_type(BlockExportType type)
 {
     BlockExport *exp, *next;

     assert(in_aio_context_home_thread(qemu_get_aio_context()));

     QLIST_FOREACH_SAFE(exp, &block_exports, next, next) {
         if (type != BLOCK_EXPORT_TYPE__MAX && exp->drv->type != type) {
             continue;
         }
         blk_exp_request_shutdown(exp);
     }

     AIO_WAIT_WHILE_UNLOCKED(NULL, blk_exp_has_type(type));
 }

 void blk_exp_close_all(void)
 {
     blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
 }

 void qmp_block_export_add(BlockExportOptions *export, Error **errp)
 {
     blk_exp_add(export, errp);
 }

 void qmp_block_export_del(const char *id,
                           bool has_mode, BlockExportRemoveMode mode,
                           Error **errp)
 {
     ERRP_GUARD();
     BlockExport *exp;

     exp = blk_exp_find(id);
     if (exp == NULL) {
         error_setg(errp, "Export '%s' is not found", id);
         return;
     }
     if (!exp->user_owned) {
         error_setg(errp, "Export '%s' is already shutting down", id);
         return;
     }

     if (!has_mode) {
         mode = BLOCK_EXPORT_REMOVE_MODE_SAFE;
     }
     if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE && exp->refcount > 1) {
         error_setg(errp, "export '%s' still in use", exp->id);
         error_append_hint(errp, "Use mode='hard' to force client "
                           "disconnect\n");
         return;
     }

     blk_exp_request_shutdown(exp);
 }

 BlockExportInfoList *qmp_query_block_exports(Error **errp)
 {
     BlockExportInfoList *head = NULL, **tail = &head;
     BlockExport *exp;

     QLIST_FOREACH(exp, &block_exports, next) {
         BlockExportInfo *info = g_new(BlockExportInfo, 1);
         *info = (BlockExportInfo) {
             .id             = g_strdup(exp->id),
             .type           = exp->drv->type,
             .node_name      = g_strdup(bdrv_get_node_name(blk_bs(exp->blk))),
             .shutting_down  = !exp->user_owned,
         };

         QAPI_LIST_APPEND(tail, info);
     }

     return head;
 }
	/*
	* Common block export infrastructure
	*
	* Copyright (c) 2012, 2020 Red Hat, Inc.
	*
	* Authors:
	* Paolo Bonzini <pbonzini@redhat.com>
	* Kevin Wolf <kwolf@redhat.com>
	*
	* This work is licensed under the terms of the GNU GPL, version 2 or
	* later. See the COPYING file in the top-level directory.
	*/

	#include "qemu/osdep.h"

	#include "block/block.h"
	#include "sysemu/block-backend.h"
	#include "sysemu/iothread.h"
	#include "block/export.h"
	#include "block/fuse.h"
	#include "block/nbd.h"
	#include "qapi/error.h"
	#include "qapi/qapi-commands-block-export.h"
	#include "qapi/qapi-events-block-export.h"
	#include "qemu/id.h"
	#ifdef CONFIG_VHOST_USER_BLK_SERVER
	#include "vhost-user-blk-server.h"
	#endif
	#ifdef CONFIG_VDUSE_BLK_EXPORT
	#include "vduse-blk.h"
	#endif

	static const BlockExportDriver *blk_exp_drivers[] = {
	&blk_exp_nbd,
	#ifdef CONFIG_VHOST_USER_BLK_SERVER
	&blk_exp_vhost_user_blk,
	#endif
	#ifdef CONFIG_FUSE
	&blk_exp_fuse,
	#endif
	#ifdef CONFIG_VDUSE_BLK_EXPORT
	&blk_exp_vduse_blk,
	#endif
	};

	/* Only accessed from the main thread */
	static QLIST_HEAD(, BlockExport) block_exports =
	QLIST_HEAD_INITIALIZER(block_exports);

	BlockExport blk_exp_find(const char id)
	{
	BlockExport *exp;

	QLIST_FOREACH(exp, &block_exports, next) {
	if (strcmp(id, exp->id) == 0) {
	return exp;
	}
	}

	return NULL;
	}

	static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
	{
	int i;

	for (i = 0; i < ARRAY_SIZE(blk_exp_drivers); i++) {
	if (blk_exp_drivers[i]->type == type) {
	return blk_exp_drivers[i];
	}
	}
	return NULL;
	}

	BlockExport blk_exp_add(BlockExportOptions export, Error **errp)
	{
	bool fixed_iothread = export->has_fixed_iothread && export->fixed_iothread;
	const BlockExportDriver *drv;
	BlockExport *exp = NULL;
	BlockDriverState *bs;
	BlockBackend *blk = NULL;
	AioContext *ctx;
	uint64_t perm;
	int ret;

	if (!id_wellformed(export->id)) {
	error_setg(errp, "Invalid block export id");
	return NULL;
	}
	if (blk_exp_find(export->id)) {
	error_setg(errp, "Block export id '%s' is already in use", export->id);
	return NULL;
	}

	drv = blk_exp_find_driver(export->type);
	if (!drv) {
	error_setg(errp, "No driver found for the requested export type");
	return NULL;
	}

	bs = bdrv_lookup_bs(NULL, export->node_name, errp);
	if (!bs) {
	return NULL;
	}

	if (!export->has_writable) {
	export->writable = false;
	}
	if (bdrv_is_read_only(bs) && export->writable) {
	error_setg(errp, "Cannot export read-only node as writable");
	return NULL;
	}

	ctx = bdrv_get_aio_context(bs);
	aio_context_acquire(ctx);

	if (export->iothread) {
	IOThread *iothread;
	AioContext *new_ctx;
	Error **set_context_errp;

	iothread = iothread_by_id(export->iothread);
	if (!iothread) {
	error_setg(errp, "iothread \"%s\" not found", export->iothread);
	goto fail;
	}

	new_ctx = iothread_get_aio_context(iothread);

	/* Ignore errors with fixed-iothread=false */
	set_context_errp = fixed_iothread ? errp : NULL;
	ret = bdrv_try_change_aio_context(bs, new_ctx, NULL, set_context_errp);
	if (ret == 0) {
	aio_context_release(ctx);
	aio_context_acquire(new_ctx);
	ctx = new_ctx;
	} else if (fixed_iothread) {
	goto fail;
	}
	}

	/*
	* Block exports are used for non-shared storage migration. Make sure
	* that BDRV_O_INACTIVE is cleared and the image is ready for write
	* access since the export could be available before migration handover.
	* ctx was acquired in the caller.
	*/
	bdrv_activate(bs, NULL);

	perm = BLK_PERM_CONSISTENT_READ;
	if (export->writable) {
	perm \|= BLK_PERM_WRITE;
	}

	blk = blk_new(ctx, perm, BLK_PERM_ALL);

	if (!fixed_iothread) {
	blk_set_allow_aio_context_change(blk, true);
	}

	ret = blk_insert_bs(blk, bs, errp);
	if (ret < 0) {
	goto fail;
	}

	if (!export->has_writethrough) {
	export->writethrough = false;
	}
	blk_set_enable_write_cache(blk, !export->writethrough);

	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,
	};

	ret = drv->create(exp, export, errp);
	if (ret < 0) {
	goto fail;
	}

	assert(exp->blk != NULL);

	QLIST_INSERT_HEAD(&block_exports, exp, next);

	aio_context_release(ctx);
	return exp;

	fail:
	if (blk) {
	blk_set_dev_ops(blk, NULL, NULL);
	blk_unref(blk);
	}
	aio_context_release(ctx);
	if (exp) {
	g_free(exp->id);
	g_free(exp);
	}
	return NULL;
	}

	/* Callers must hold exp->ctx lock */
	void blk_exp_ref(BlockExport *exp)
	{
	assert(exp->refcount > 0);
	exp->refcount++;
	}

	/* Runs in the main thread */
	static void blk_exp_delete_bh(void *opaque)
	{
	BlockExport *exp = opaque;
	AioContext *aio_context = exp->ctx;

	aio_context_acquire(aio_context);

	assert(exp->refcount == 0);
	QLIST_REMOVE(exp, next);
	exp->drv->delete(exp);
	blk_set_dev_ops(exp->blk, NULL, NULL);
	blk_unref(exp->blk);
	qapi_event_send_block_export_deleted(exp->id);
	g_free(exp->id);
	g_free(exp);

	aio_context_release(aio_context);
	}

	/* Callers must hold exp->ctx lock */
	void blk_exp_unref(BlockExport *exp)
	{
	assert(exp->refcount > 0);
	if (--exp->refcount == 0) {
	/* Touch the block_exports list only in the main thread */
	aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh,
	exp);
	}
	}

	/*
	* Drops the user reference to the export and requests that all client
	* connections and other internally held references start to shut down. When
	* the function returns, there may still be active references while the export
	* is in the process of shutting down.
	*
	* Acquires exp->ctx internally. Callers must not hold the lock.
	*/
	void blk_exp_request_shutdown(BlockExport *exp)
	{
	AioContext *aio_context = exp->ctx;

	aio_context_acquire(aio_context);

	/*
	* If the user doesn't own the export any more, it is already shutting
	* down. We must not call .request_shutdown and decrease the refcount a
	* second time.
	*/
	if (!exp->user_owned) {
	goto out;
	}

	exp->drv->request_shutdown(exp);

	assert(exp->user_owned);
	exp->user_owned = false;
	blk_exp_unref(exp);

	out:
	aio_context_release(aio_context);
	}

	/*
	* Returns whether a block export of the given type exists.
	* type == BLOCK_EXPORT_TYPE__MAX checks for an export of any type.
	*/
	static bool blk_exp_has_type(BlockExportType type)
	{
	BlockExport *exp;

	if (type == BLOCK_EXPORT_TYPE__MAX) {
	return !QLIST_EMPTY(&block_exports);
	}

	QLIST_FOREACH(exp, &block_exports, next) {
	if (exp->drv->type == type) {
	return true;
	}
	}

	return false;
	}

	/* type == BLOCK_EXPORT_TYPE__MAX for all types */
	void blk_exp_close_all_type(BlockExportType type)
	{
	BlockExport exp, next;

	assert(in_aio_context_home_thread(qemu_get_aio_context()));

	QLIST_FOREACH_SAFE(exp, &block_exports, next, next) {
	if (type != BLOCK_EXPORT_TYPE__MAX && exp->drv->type != type) {
	continue;
	}
	blk_exp_request_shutdown(exp);
	}

	AIO_WAIT_WHILE_UNLOCKED(NULL, blk_exp_has_type(type));
	}

	void blk_exp_close_all(void)
	{
	blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
	}

	void qmp_block_export_add(BlockExportOptions export, Error *errp)
	{
	blk_exp_add(export, errp);
	}

	void qmp_block_export_del(const char *id,
	bool has_mode, BlockExportRemoveMode mode,
	Error **errp)
	{
	ERRP_GUARD();
	BlockExport *exp;

	exp = blk_exp_find(id);
	if (exp == NULL) {
	error_setg(errp, "Export '%s' is not found", id);
	return;
	}
	if (!exp->user_owned) {
	error_setg(errp, "Export '%s' is already shutting down", id);
	return;
	}

	if (!has_mode) {
	mode = BLOCK_EXPORT_REMOVE_MODE_SAFE;
	}
	if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE && exp->refcount > 1) {
	error_setg(errp, "export '%s' still in use", exp->id);
	error_append_hint(errp, "Use mode='hard' to force client "
	"disconnect\n");
	return;
	}

	blk_exp_request_shutdown(exp);
	}

	BlockExportInfoList qmp_query_block_exports(Error *errp)
	{
	BlockExportInfoList head = NULL, *tail = &head;
	BlockExport *exp;

	QLIST_FOREACH(exp, &block_exports, next) {
	BlockExportInfo *info = g_new(BlockExportInfo, 1);
	*info = (BlockExportInfo) {
	.id = g_strdup(exp->id),
	.type = exp->drv->type,
	.node_name = g_strdup(bdrv_get_node_name(blk_bs(exp->blk))),
	.shutting_down = !exp->user_owned,
	};

	QAPI_LIST_APPEND(tail, info);
	}

	return head;
	}