diff options
| author | Stefan Hajnoczi <stefanha@redhat.com> | 2022-06-09 17:47:12 +0100 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2022-06-15 16:43:42 +0100 |
| commit | 99b969fbe105117f5af6060d3afef40ca39cc9c1 (patch) | |
| tree | 86bb7301ad0f534513a53984d0d3c17a1740f453 | |
| parent | f387cac5af030a58ac5a0dacf64cab5e5a4fe5c7 (diff) | |
linux-aio: explain why max batch is checked in laio_io_unplug()
It may not be obvious why laio_io_unplug() checks max batch. I discussed
this with Stefano and have added a comment summarizing the reason.
Cc: Stefano Garzarella <sgarzare@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20220609164712.1539045-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
| -rw-r--r-- | block/linux-aio.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/block/linux-aio.c b/block/linux-aio.c index 6078da7e42..9c2393a2f7 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -365,6 +365,12 @@ void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s, assert(s->io_q.plugged); s->io_q.plugged--; + /* + * Why max batch checking is performed here: + * Another BDS may have queued requests with a higher dev_max_batch and + * therefore in_queue could now exceed our dev_max_batch. Re-check the max + * batch so we can honor our device's dev_max_batch. + */ if (s->io_q.in_queue >= laio_max_batch(s, dev_max_batch) || (!s->io_q.plugged && !s->io_q.blocked && !QSIMPLEQ_EMPTY(&s->io_q.pending))) { |