[Devel] [PATCH rh7] fuse: resend interrupted release

[Konstantin Khorenko]

Maxim, should this patch be sent to mainstream as well?

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

On 03/30/2016 03:58 AM, Maxim Patlasov wrote:
> If a client gets fatal signal while explicitly waiting for ACK from fused
> (request_wait_answer()), kernel fuse discards the request like this:
>
>> 		/* Request is not yet in userspace, bail out */
>> 		if (req->state == FUSE_REQ_PENDING) {
>> 			list_del(&req->list);
>> 			__fuse_put_request(req);
>> 			req->out.h.error = -EINTR;
>> 			return;
>> 		}
>
> This is nice for requests directly initiated by client, but not for RELEASE
> requests: we have to avoid discarding RELEASE requests because otherwise
> fused won't know when the file is "closed" by client (last fput called).
>
> The problem didn't exist before close_wait feature because then fuse_file_put
> sent RELEASE asynchronously. Hence no request_wait_answer() involved.
>
> The patch solves the problem by resending interrupted RELEASE asynchronously.
> This is OK because if the client is killed, he/she doesn't care about
> sync/async close(2) behavior.
>
> https://jira.sw.ru/browse/PSBM-45428
>
> Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
> ---
>   fs/fuse/file.c |    6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index f432b70..11c5959 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -155,10 +155,16 @@ static void fuse_file_put(struct fuse_file *ff, bool sync)
>   		if (sync) {
>   			req->background = 0;
>   			fuse_request_send(ff->fc, req);
> +			if (req->out.h.error == -EINTR) {
> +				req->state = FUSE_REQ_INIT;
> +				req->out.h.error = 0;
> +				goto async_fallback;
> +			}
>   			fuse_file_list_del(ff);
>   			path_put(&req->misc.release.path);
>   			fuse_put_request(ff->fc, req);
>   		} else {
> +async_fallback:
>   			fuse_file_list_del(ff);
>   			req->end = fuse_release_end;
>   			req->background = 1;
>
> .
>