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commit 4017afe28d640c535109576bd149bc7e0345f075
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Author: Rajesh Ghanekar <rajesh_ghanekar@symantec.com>
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Date: Wed Aug 20 14:00:59 2014 -0400
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nfs-utils: Allow turning off nfsv3 readdir_plus
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One of our customer's application only needs file names, not file
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attributes. With directories having 10K+ inodes (assuming buffer cache
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has directory blocks cached having file names, but inode cache is
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limited and hence need eviction of older cached inodes), older inodes
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are evicted periodically. So if they keep on doing readdir(2) from NSF
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client on multiple directories, some directory's files are periodically
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removed from inode cache and hence new readdir(2) on same directory
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requires disk access to bring back inodes again to inode cache.
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As READDIRPLUS request fetches attributes also, doing getattr on each
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file on server, it causes unnecessary disk accesses. If READDIRPLUS on
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NFS client is returned with -ENOTSUPP, NFS client uses READDIR request
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which just gets the names of the files in a directory, not attributes,
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hence avoiding disk accesses on server.
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There's already a corresponding client-side mount option, but an export
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option reduces the need for configuration across multiple clients.
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This flag affects NFSv3 only. If it turns out it's needed for NFSv4 as
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well then we may have to figure out how to extend the behavior to NFSv4,
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but it's not currently obvious how to do that.
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Signed-off-by: Rajesh Ghanekar <rajesh_ghanekar@symantec.com>
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Signed-off-by: Steve Dickson <steved@redhat.com>
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diff --git a/support/include/nfs/export.h b/support/include/nfs/export.h
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index 1547a87..2f59e6a 100644
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--- a/support/include/nfs/export.h
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+++ b/support/include/nfs/export.h
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@@ -17,7 +17,8 @@
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#define NFSEXP_ALLSQUASH 0x0008
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#define NFSEXP_ASYNC 0x0010
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#define NFSEXP_GATHERED_WRITES 0x0020
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-/* 40, 80, 100 unused */
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+#define NFSEXP_NOREADDIRPLUS 0x0040
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+/* 80, 100 unused */
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#define NFSEXP_NOHIDE 0x0200
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#define NFSEXP_NOSUBTREECHECK 0x0400
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#define NFSEXP_NOAUTHNLM 0x0800
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diff --git a/support/nfs/exports.c b/support/nfs/exports.c
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index 819d6c4..eb782b9 100644
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--- a/support/nfs/exports.c
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+++ b/support/nfs/exports.c
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@@ -273,6 +273,8 @@ putexportent(struct exportent *ep)
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"in" : "");
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fprintf(fp, "%sacl,", (ep->e_flags & NFSEXP_NOACL)?
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"no_" : "");
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+ if (ep->e_flags & NFSEXP_NOREADDIRPLUS)
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+ fprintf(fp, "nordirplus,");
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if (ep->e_flags & NFSEXP_FSID) {
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fprintf(fp, "fsid=%d,", ep->e_fsid);
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}
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@@ -539,6 +541,8 @@ parseopts(char *cp, struct exportent *ep, int warn, int *had_subtree_opt_ptr)
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clearflags(NFSEXP_ASYNC, active, ep);
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else if (!strcmp(opt, "async"))
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setflags(NFSEXP_ASYNC, active, ep);
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+ else if (!strcmp(opt, "nordirplus"))
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+ setflags(NFSEXP_NOREADDIRPLUS, active, ep);
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else if (!strcmp(opt, "nohide"))
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setflags(NFSEXP_NOHIDE, active, ep);
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else if (!strcmp(opt, "hide"))
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diff --git a/utils/exportfs/exports.man b/utils/exportfs/exports.man
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index e8b29df..3d974d9 100644
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--- a/utils/exportfs/exports.man
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+++ b/utils/exportfs/exports.man
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@@ -360,6 +360,11 @@ supported so the same configuration can be made to work on old and new
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kernels alike.
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.TP
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+.IR nordirplus
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+This option will disable READDIRPLUS request handling. When set,
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+READDIRPLUS requests from NFS clients return NFS3ERR_NOTSUPP, and
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+clients fall back on READDIR. This option affects only NFSv3 clients.
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+.TP
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.IR refer= path@host[+host][:path@host[+host]]
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A client referencing the export point will be directed to choose from
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the given list an alternative location for the filesystem.
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