nfsd: allow turning off nfsv3 readdir_plus (18c01ab3) · Commits · 戴 / test

One of our customer's application only needs file names, not file attributes. With directories having 10K+ inodes (assuming buffer cache has directory blocks cached having file names, but inode cache is limited and hence need eviction of older cached inodes), older inodes are evicted periodically. So if they keep on doing readdir(2) from NSF client on multiple directories, some directory's files are periodically removed from inode cache and hence new readdir(2) on same directory requires disk access to bring back inodes again to inode cache. As READDIRPLUS request fetches attributes also, doing getattr on each file on server, it causes unnecessary disk accesses. If READDIRPLUS on NFS client is returned with -ENOTSUPP, NFS client uses READDIR request which just gets the names of the files in a directory, not attributes, hence avoiding disk accesses on server. There's already a corresponding client-side mount option, but an export option reduces the need for configuration across multiple clients. This flag affects NFSv3 only. If it turns out it's needed for NFSv4 as well then we may have to figure out how to extend the behavior to NFSv4, but it's not currently obvious how to do that. Signed-off-by:

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

J. Bruce Fields <bfields@redhat.com>

fs/nfsd/export.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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", ""}},

fs/nfsd/nfs3proc.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -466,6 +466,14 @@ 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,

include/uapi/linux/nfsd/export.h

+3 −2

Original line number	Diff line number	Diff line
		@@ -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 \

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