On Mon, Oct 03, 2016 at 09:51:49AM +0200, Wouter Verhelst wrote: > Actually, I was pointing out the TCP head-of-line issue, where a delay > on the socket that contains the flush reply would result in the arrival > in the kernel block layer of a write reply before the said flush reply, > resulting in a write being considered part of the flush when in fact it > was not. The kernel (or any other user of SCSI/ATA/NVMe-like cache flushes) will wait for all I/O that needs to be in the cache for explicitly, so this is not a problem. > Can you clarify what you mean by that? Why is it an "odd flush > definition", and how would you "properly" define it? E.g. take the defintion from NVMe which also supports multiple queues: "The Flush command shall commit data and metadata associated with the specified namespace(s) to non-volatile media. The flush applies to all commands completed prior to the submission of the Flush command. The controller may also flush additional data and/or metadata from any namespace." The focus is completed - we need to get a reply to the host first before we can send the flush command, so anything that we require to be flushed needs to explicitly be completed first. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
