Move this function into a coroutine so we can convert the whole
qmp_query_block command into a coroutine in the next patches.
Placing the entire command in a coroutine allow us to yield all the
way back to the main loop, releasing the BQL and unblocking the main
loop.
When the whole conversion is completed, we'll be able to avoid a
priority inversion that happens when a QMP command calls a slow
(buggy) system call and blocks the vcpu thread from doing mmio due to
contention on the BQL.
About coroutine safety:
Most callees have coroutine versions themselves and thus are safe to
call in a coroutine. The remaining ones:
- bdrv_refresh_filename, bdrv_get_full_backing_filename: String
manipulation, nothing that would be unsafe for use in coroutines;
- bdrv_get_format_name: Just accesses a field;
- bdrv_get_specific_info, bdrv_query_snapshot_info_list: No locks or
anything that would poll or block.
(using a mixed wrapper for now, but after all callers are converted,
this can become a coroutine exclusively)
Link: https://lore.kernel.org/r/20240409145917.6780-1-farosas@suse.de
References: bsc#1211000
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
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