On Mon, Nov 04, 2024 at 03:47:42PM +1100, NeilBrown wrote:
>
> An NFSv4.2 COPY request can explicitly request a synchronous copy. If
> that is not requested then the server is free to perform the copy
> synchronously or asynchronously.
>
> In the Linux implementation an async copy requires more resources than a
> sync copy. If nfsd cannot allocate these resources, the best response
> is to simply perform the copy (or the first 4MB of it) synchronously.
>
> This choice may be debatable if the unavailable resource was due to
> memory allocation failure - when memalloc fails it might be best to
> simply give up as the server is clearly under load. However in the case
> that policy prevents another kthread being created there is no benefit
> and much cost is failing with NFS4ERR_DELAY. In that case it seems
> reasonable to avoid that error in all circumstances.
>
> So change the out_err case to retry as a sync copy.
>
> Fixes: aadc3bbea163 ("NFSD: Limit the number of concurrent async COPY operations")
Hi Neil,
Why is a Fixes: tag necessary?
And why that commit? async copies can fail due to lack of resources
on kernels that don't have aadc3bbea163, AFAICT.
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> ---
> fs/nfsd/nfs4proc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index fea171ffed62..06e0d9153ca9 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -1972,6 +1972,7 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> wake_up_process(async_copy->copy_task);
> status = nfs_ok;
> } else {
> + retry_sync:
> status = nfsd4_do_copy(copy, copy->nf_src->nf_file,
> copy->nf_dst->nf_file, true);
> }
> @@ -1990,8 +1991,7 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> }
> if (async_copy)
> cleanup_async_copy(async_copy);
> - status = nfserr_jukebox;
> - goto out;
> + goto retry_sync;
> }
>
> static struct nfsd4_copy *
>
> base-commit: 26e6e693936986309c01e8bb80e318d63fda4a44
> --
> 2.47.0
>
--
Chuck Lever
