From d3684397ea9ba2edf02be0aa2b4dcab3bd74c503 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Fri, 15 Aug 2025 19:29:55 -0400 Subject: [PATCH] nfs/localio: avoid bouncing LOCALIO if nfs_client_is_local() Previously nfs_local_probe() was made to disable and then attempt to re-enable LOCALIO (via LOCALIO protocol handshake) if/when it was called and LOCALIO already enabled. Vague memory for _why_ this was the case is that this was useful if/when a local NFS server were to be restarted with a local NFS client connected to it. But as it happens this causes an absurd amount of LOCALIO flapping which has a side-effect of too much IO being needlessly sent to NFSD (using RPC over the loopback network interface). This is the definition of "serious performance loss" (that negates the point of having LOCALIO). So remove this mis-optimization for re-enabling LOCALIO if/when an NFS server is restarted (which is an extremely rare thing to do). Will revisit testing that scenario again but in the meantime this patch restores the full benefit of LOCALIO. Signed-off-by: Mike Snitzer Reviewed-by: Jeff Layton Reviewed-by: NeilBrown Signed-off-by: Trond Myklebust --- fs/nfs/localio.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c index bdb82a19136aa..97abf62f109d2 100644 --- a/fs/nfs/localio.c +++ b/fs/nfs/localio.c @@ -180,10 +180,8 @@ static void nfs_local_probe(struct nfs_client *clp) return; } - if (nfs_client_is_local(clp)) { - /* If already enabled, disable and re-enable */ - nfs_localio_disable_client(clp); - } + if (nfs_client_is_local(clp)) + return; if (!nfs_uuid_begin(&clp->cl_uuid)) return; @@ -244,7 +242,8 @@ __nfs_local_open_fh(struct nfs_client *clp, const struct cred *cred, case -ENOMEM: case -ENXIO: case -ENOENT: - /* Revalidate localio, will disable if unsupported */ + /* Revalidate localio */ + nfs_localio_disable_client(clp); nfs_local_probe(clp); } } -- 2.47.3