[SPDK] Re: Why does the flush operation in bdev_nvme do nothing?

I think you can submit a fix patch.

If FLUSH IO type is supported, then call spdk_nvme_ns_cmd_flush.

> -----Original Message-----
> From: fandahao17(a)mail.ustc.edu.cn <fandahao17(a)mail.ustc.edu.cn>
> Sent: Monday, January 25, 2021 7:51 PM
> To: spdk(a)lists.01.org
> Subject: [SPDK] Why does the flush operation in bdev_nvme do nothing?
> 
> Hi, there! I ran into the following code in module/bdev/nvme/bdev_nvme.c
> when I wanted to force a flush into my SSD to make sure all my previous writes
> are durable.
> 
> static int
> bdev_nvme_flush(struct spdk_nvme_ns *ns, struct spdk_nvme_qpair *qpair,
> 		struct nvme_bdev_io *bio, uint64_t offset, uint64_t nbytes)
> {
> 	spdk_bdev_io_complete(spdk_bdev_io_from_ctx(bio),
> SPDK_BDEV_IO_STATUS_SUCCESS);
> 	return 0;
> }
> 
> Seems that it just completes without issuing any nvme FLUSH commands. This
> interests me because I thought it would call something like
> spdk_nvme_ns_cmd_flush(). I am curious how can I make sure the data is
> written into the non-volatile media of the SSD? Can I still guarantee the write-
> read order without using a FLUSH operation in between? Thanks!
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