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block/export: add iothread and fixed-iothread options

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Make it possible to specify the iothread where the export will run. By
default the block node can be moved to other AioContexts later and the
export will follow. The fixed-iothread option forces strict behavior
that prevents changing AioContext while the export is active. See the
QAPI docs for details.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200929125516.186715-5-stefanha@redhat.com
[Fix stray '#' character in block-export.json and add missing "(since:
5.2)" as suggested by Eric Blake.
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-09-29 13:55:16 +01:00
parent cbc20bfb8f
commit f51d23c80a
4 changed files with 45 additions and 4 deletions
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31
block/export/export.c
View file

@ -15,6 +15,7 @@
#include "block/block.h"
#include "sysemu/block-backend.h"
#include "sysemu/iothread.h"
#include "block/export.h"
#include "block/nbd.h"
#include "qapi/error.h"
@ -63,10 +64,11 @@ static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
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;
BlockBackend *blk = NULL;
AioContext *ctx;
uint64_t perm;
int ret;
@ -102,6 +104,28 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
if (export->has_iothread) {
IOThread *iothread;
AioContext *new_ctx;
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);
ret = bdrv_try_set_aio_context(bs, new_ctx, 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
@ -116,6 +140,11 @@ BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
}
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;