Hi Shaun,
> On 25 May 2017, at 01:20, Shaun McDowell <shaunjmcdowell@...17...> wrote:
>
> Not sure if this is the place for nbd kernel code changes but we hit a problem where we were never receiving commands with the fua flag set on our nbd server (running on ubuntu 16.04 lts with 4.4.0-78 kernel)
You probably want to explicitly copy the kernel maintainer Josef Bacik <jbacik@...2204...> and the normal lkml lists, but a big +1 for the code change. I'm not qualified to fully review the patch, but I'd love the kernel to support FUA properly.
You might want to separate the debug stuff into a separate patch.
> After digging into the nbd kernel module code it turns out that the linux kernel module is not handling the NBD_FLAG_SEND_FUA and was not setting REQ_FUA on the request queue.
>
> Here is a patch to enable FUA writes on the queue and then detect them in the req->cmd_flags and set the appropriate bit in the request.type field for the server.
>
> This patch also includes a fix to the /sys/kernel/debug/nbd/*/flags file that was being incorrectly called resulting in garbage to the debug file instead of the flags that we came across while trying to decipher why we weren't receiving the fua cmds.
>
> I've never contributed code to the linux kernel before so if this isn't the right place then if someone more knowledgeable on the linux kernel nbd module maintainer could direct me to him/her I would appreciate it.
> <nbd-fua.patch>--------------------------------------------- ------------------------------ ---
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Alex Bligh