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block: Convert 'block_resize' to coroutine 

block_resize performs some I/O that could potentially take quite some
time, so use it as an example for the new 'coroutine': true annotation
in the QAPI schema.

bdrv_truncate() requires that we're already in the right AioContext for
the BlockDriverState if called in coroutine context. So instead of just
taking the AioContext lock, move the QMP handler coroutine to the
context.

Call blk_unref() only after switching back because blk_unref() may only
be called in the main thread.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20201005155855.256490-15-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
Kevin Wolf 2020-10-05 17:58:55 +02:00 committed by Markus Armbruster
parent 18c6ac1c6e
commit eb94b81a94
3 changed files with 11 additions and 9 deletions
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16
blockdev.c
View File

@ -2449,14 +2449,14 @@ BlockDirtyBitmapSha256 *qmp_x_debug_block_dirty_bitmap_sha256(const char *node,
return ret;
}
void qmp_block_resize(bool has_device, const char *device,
bool has_node_name, const char *node_name,
int64_t size, Error **errp)
void coroutine_fn qmp_block_resize(bool has_device, const char *device,
bool has_node_name, const char *node_name,
int64_t size, Error **errp)
{
Error *local_err = NULL;
BlockBackend *blk = NULL;
BlockDriverState *bs;
AioContext *aio_context;
AioContext *old_ctx;
bs = bdrv_lookup_bs(has_device ? device : NULL,
has_node_name ? node_name : NULL,
@ -2466,9 +2466,6 @@ void qmp_block_resize(bool has_device, const char *device,
return;
}
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
if (size < 0) {
error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "size", "a >0 size");
goto out;
@ -2485,12 +2482,15 @@ void qmp_block_resize(bool has_device, const char *device,
}
bdrv_drained_begin(bs);
old_ctx = bdrv_co_enter(bs);
blk_truncate(blk, size, false, PREALLOC_MODE_OFF, 0, errp);
bdrv_co_leave(bs, old_ctx);
bdrv_drained_end(bs);
out:
bdrv_co_lock(bs);
blk_unref(blk);
aio_context_release(aio_context);
bdrv_co_unlock(bs);
}
void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,

1
hmp-commands.hx
View File

@ -76,6 +76,7 @@ ERST
.params = "device size",
.help = "resize a block image",
.cmd = hmp_block_resize,
.coroutine = true,
},
SRST

3
qapi/block-core.json
View File

@ -1310,7 +1310,8 @@
{ 'command': 'block_resize',
'data': { '*device': 'str',
'*node-name': 'str',
'size': 'int' } }
'size': 'int' },
'coroutine': true }
##
# @NewImageMode: