RE: [PATCH] nfsd: allow turning off nfsv3 readdir_plus

[Rajesh Ghanekar <Rajesh_Ghanekar@symantec.com>]

Hi Bruce, Steve,
       Here is the nfs-utils patch reworked. Sorry for top posting, though.
We had to wait for internal legal approval to complete, and hence
got delayed. Same "signed-off" by signature can go to nfsd kernel
patch which you have reworked. Please let me know if I need to
resend (copy from your mail with signed-off added) nfsd kernel patch.

Signed-off-by: Rajesh Ghanekar <rajesh_ghanekar@symantec.com>


diff -uprN nfs-utils-1.3.0.old/support/include/nfs/export.h nfs-utils-1.3.0/support/include/nfs/export.h
--- nfs-utils-1.3.0.old/support/include/nfs/export.h	2014-03-25 20:42:07.000000000 +0530
+++ nfs-utils-1.3.0/support/include/nfs/export.h	2014-08-18 22:28:24.420262810 +0530
@@ -17,7 +17,8 @@
 #define NFSEXP_ALLSQUASH	0x0008
 #define NFSEXP_ASYNC		0x0010
 #define NFSEXP_GATHERED_WRITES	0x0020
-/* 40, 80, 100 unused */
+#define NFSEXP_NOREADDIRPLUS	0x0040
+/* 80, 100 unused */
 #define NFSEXP_NOHIDE		0x0200
 #define NFSEXP_NOSUBTREECHECK	0x0400
 #define NFSEXP_NOAUTHNLM	0x0800
diff -uprN nfs-utils-1.3.0.old/support/nfs/exports.c nfs-utils-1.3.0/support/nfs/exports.c
--- nfs-utils-1.3.0.old/support/nfs/exports.c	2014-03-25 20:42:07.000000000 +0530
+++ nfs-utils-1.3.0/support/nfs/exports.c	2014-08-18 22:28:24.600262814 +0530
@@ -273,6 +273,8 @@ putexportent(struct exportent *ep)
 		"in" : "");
 	fprintf(fp, "%sacl,", (ep->e_flags & NFSEXP_NOACL)?
 		"no_" : "");
+	if (ep->e_flags & NFSEXP_NOREADDIRPLUS)
+		fprintf(fp, "nordirplus,");
 	if (ep->e_flags & NFSEXP_FSID) {
 		fprintf(fp, "fsid=%d,", ep->e_fsid);
 	}
@@ -539,6 +541,8 @@ parseopts(char *cp, struct exportent *ep
 			clearflags(NFSEXP_ASYNC, active, ep);
 		else if (!strcmp(opt, "async"))
 			setflags(NFSEXP_ASYNC, active, ep);
+		else if (!strcmp(opt, "nordirplus"))
+			setflags(NFSEXP_NOREADDIRPLUS, active, ep);
 		else if (!strcmp(opt, "nohide"))
 			setflags(NFSEXP_NOHIDE, active, ep);
 		else if (!strcmp(opt, "hide"))
diff -uprN nfs-utils-1.3.0.old/utils/exportfs/exports.man nfs-utils-1.3.0/utils/exportfs/exports.man
--- nfs-utils-1.3.0.old/utils/exportfs/exports.man	2014-03-25 20:42:07.000000000 +0530
+++ nfs-utils-1.3.0/utils/exportfs/exports.man	2014-08-18 22:27:23.360261358 +0530
@@ -360,6 +360,13 @@ supported so the same configuration can
 kernels alike.
 
 .TP
+.IR nordirplus
+This option will allow disabling READDIRPLUS request handling.
+When enabled, READDIRPLUS requests from NFS client will be returned
+with "not supported" reply. Most of the NFS client implementations
+starts to use READDIR request if READDIRPLUS is returned with
+"not supported" reply. This option is only applicable for NFSv3.
+.TP
 .IR refer= path@host[+host][:path@host[+host]]
 A client referencing the export point will be directed to choose from
 the given list an alternative location for the filesystem.


Thanks,
Rajesh

-----Original Message-----
From: J. Bruce Fields [mailto:bfields@fieldses.org] 
Sent: Tuesday, August 05, 2014 11:52 PM
To: Steve Dickson
Cc: Rishi Agrawal; linux-nfs@vger.kernel.org; Rajesh Ghanekar; Ram Pandiri; Sreeharsha Sarabu; Abhijit Dey; Tushar Shinde; bfields@redhat.com
Subject: Re: [PATCH] nfsd: allow turning off nfsv3 readdir_plus

On Mon, Aug 04, 2014 at 05:46:47PM -0400, J. Bruce Fields wrote:
> On Mon, Aug 04, 2014 at 11:24:11AM -0400, bfields wrote:
> > +static int
> > +nfsd3_is_readdirplus_supported(struct svc_rqst *rqstp, struct 
> > +svc_fh *fhp) {
> > +	struct svc_export *exp;
> > +	int supported = 1; /* fall back to readdirplus supported in case of errors.*/
> > +	int err;
> > +
> > +	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_READ);
> > +	if (err) {
> > +		goto out;
> > +	}
> 
> Actually, this isn't right: errors from fh_verify should be returned 
> to the client or weird things could happen (e.g. what should have been 
> a transient DELAY error could result in the client turning off 
> readdirplus).

Apologies, I misread: as the comment above notes, it falls back on allowing readdirplus when this fails, so I don't think there's a real bug here.

> And MAY_READ is more than nfsd_readdir actually asks for, I think, 
> probably should just be MAY_NOP here.
> 
> I'll fix that up.--b.

But it's probably still better to return the fh_verify error on failure, as follows.

--b.

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c index 72ffd7cce3c3..30a739d896ff 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -1145,6 +1145,7 @@ static struct flags {
 	{ NFSEXP_ALLSQUASH, {"all_squash", ""}},
 	{ NFSEXP_ASYNC, {"async", "sync"}},
 	{ NFSEXP_GATHERED_WRITES, {"wdelay", "no_wdelay"}},
+	{ NFSEXP_NOREADDIRPLUS, {"nordirplus", ""}},
 	{ NFSEXP_NOHIDE, {"nohide", ""}},
 	{ NFSEXP_CROSSMOUNT, {"crossmnt", ""}},
 	{ NFSEXP_NOSUBTREECHECK, {"no_subtree_check", ""}}, diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c index fa2525b2e9d7..247b06fb400d 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -471,6 +471,14 @@ nfsd3_proc_readdirplus(struct svc_rqst *rqstp, struct nfsd3_readdirargs *argp,
 	resp->buflen = resp->count;
 	resp->rqstp = rqstp;
 	offset = argp->cookie;
+
+	nfserr = fh_verify(rqstp, &resp->fh, S_IFDIR, NFSD_MAY_NOP);
+	if (nfserr)
+		RETURN_STATUS(nfserr);
+
+	if (resp->fh.fh_export->ex_flags & NFSEXP_NOREADDIRPLUS)
+		RETURN_STATUS(nfserr_notsupp);
+
 	nfserr = nfsd_readdir(rqstp, &resp->fh,
 				     &offset,
 				     &resp->common,
diff --git a/include/uapi/linux/nfsd/export.h b/include/uapi/linux/nfsd/export.h
index cf47c313794e..584b6ef3a5e8 100644
--- a/include/uapi/linux/nfsd/export.h
+++ b/include/uapi/linux/nfsd/export.h
@@ -28,7 +28,8 @@
 #define NFSEXP_ALLSQUASH	0x0008
 #define NFSEXP_ASYNC		0x0010
 #define NFSEXP_GATHERED_WRITES	0x0020
-/* 40 80 100 currently unused */
+#define NFSEXP_NOREADDIRPLUS    0x0040
+/* 80 100 currently unused */
 #define NFSEXP_NOHIDE		0x0200
 #define NFSEXP_NOSUBTREECHECK	0x0400
 #define	NFSEXP_NOAUTHNLM	0x0800		/* Don't authenticate NLM requests - just trust */
@@ -47,7 +48,7 @@
  */
 #define	NFSEXP_V4ROOT		0x10000
 /* All flags that we claim to support.  (Note we don't support NOACL.) */
-#define NFSEXP_ALLFLAGS		0x17E3F
+#define NFSEXP_ALLFLAGS		0x1FE7F
 
 /* The flags that may vary depending on security flavor: */
 #define NFSEXP_SECINFO_FLAGS	(NFSEXP_READONLY | NFSEXP_ROOTSQUASH \