Re: [PATCH v14 00/25] nfs/nfsd: add support for LOCALIO

[Mike Snitzer <snitzer@kernel.org>]

On Wed, Aug 28, 2024 at 09:03:55PM -0400, Mike Snitzer wrote:
> These latest changes are available in my git tree here:
> https://git.kernel.org/pub/scm/linux/kernel/git/snitzer/linux.git/log/?h=nfs-localio-for-next
> 
> I _think_ I addressed all of v13's very helpful review comments.
> Special thanks to Neil and Chuck for their time and help!
> 
> And hopefully I didn't miss anything in the changelog below.

As it happens, a last minute rebase that I did just before sending out
v14 caused me to send out 2 stale patches:
[PATCH v14 09/25] nfsd: add nfsd_file_acquire_local()
[PATCH v14 25/25] nfs: add FAQ section to Documentation/filesystems/nfs/localio.rst

I will reply to each patch with a correct v14.5 for each.

Sorry for the confusion.

Here is the incremental diff that shows what was missing in v14:

diff --git a/Documentation/filesystems/nfs/localio.rst b/Documentation/filesystems/nfs/localio.rst
index 4b6d63246479..5d652f637a97 100644
--- a/Documentation/filesystems/nfs/localio.rst
+++ b/Documentation/filesystems/nfs/localio.rst
@@ -120,12 +120,13 @@ FAQ
    using RPC, beneficial?  Is the benefit pNFS specific?
 
    Avoiding the use of XDR and RPC for file opens is beneficial to
-   performance regardless of whether pNFS is used. However adding a
-   requirement to go over the wire to do an open and/or close ends up
-   negating any benefit of avoiding the wire for doing the I/O itself
-   when we´re dealing with small files. There is no benefit to replacing
-   the READ or WRITE with a new open and/or close operation that still
-   needs to go over the wire.
+   performance regardless of whether pNFS is used. Especially when
+   dealing with small files its best to avoid going over the wire
+   whenever possible, otherwise it could reduce or even negate the
+   benefits of avoiding the wire for doing the small file I/O itself.
+   Given LOCALIO's requirements the current approach of having the
+   client perform a server-side file open, without using RPC, is ideal.
+   If in the future requirements change then we can adapt accordingly.
 
 7. Why is LOCALIO only supported with UNIX Authentication (AUTH_UNIX)?
 
diff --git a/fs/nfsd/lockd.c b/fs/nfsd/lockd.c
index e636d2a1e664..46a7f9b813e5 100644
--- a/fs/nfsd/lockd.c
+++ b/fs/nfsd/lockd.c
@@ -32,10 +32,8 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
 	int		access;
 	struct svc_fh	fh;
 
-	if (rqstp->rq_vers == 4)
-		fh_init(&fh, NFS3_FHSIZE);
-	else
-		fh_init(&fh, NFS_FHSIZE);
+	/* must initialize before using! but maxsize doesn't matter */
+	fh_init(&fh,0);
 	fh.fh_handle.fh_size = f->size;
 	memcpy(&fh.fh_handle.fh_raw, f->data, f->size);
 	fh.fh_export = NULL;
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 49468e478d23..eca577cf3263 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -290,9 +290,6 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net,
 			fhp->fh_use_wgather = true;
 		if (exp->ex_flags & NFSEXP_V4ROOT)
 			goto out;
-		break;
-	case 0:
-		WARN_ONCE(1, "Uninitialized file handle");
 	}
 
 	return 0;