18c01ab302
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>
59 lines
1.9 KiB
C
59 lines
1.9 KiB
C
/*
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* include/linux/nfsd/export.h
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*
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* Public declarations for NFS exports. The definitions for the
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* syscall interface are in nfsctl.h
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*
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* Copyright (C) 1995-1997 Olaf Kirch <okir@monad.swb.de>
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*/
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#ifndef _UAPINFSD_EXPORT_H
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#define _UAPINFSD_EXPORT_H
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# include <linux/types.h>
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/*
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* Important limits for the exports stuff.
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*/
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#define NFSCLNT_IDMAX 1024
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#define NFSCLNT_ADDRMAX 16
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#define NFSCLNT_KEYMAX 32
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/*
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* Export flags.
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*/
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#define NFSEXP_READONLY 0x0001
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#define NFSEXP_INSECURE_PORT 0x0002
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#define NFSEXP_ROOTSQUASH 0x0004
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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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#define NFSEXP_NOREADDIRPLUS 0x0040
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/* 80 100 currently 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 /* Don't authenticate NLM requests - just trust */
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#define NFSEXP_MSNFS 0x1000 /* do silly things that MS clients expect; no longer supported */
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#define NFSEXP_FSID 0x2000
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#define NFSEXP_CROSSMOUNT 0x4000
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#define NFSEXP_NOACL 0x8000 /* reserved for possible ACL related use */
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/*
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* The NFSEXP_V4ROOT flag causes the kernel to give access only to NFSv4
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* clients, and only to the single directory that is the root of the
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* export; further lookup and readdir operations are treated as if every
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* subdirectory was a mountpoint, and ignored if they are not themselves
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* exported. This is used by nfsd and mountd to construct the NFSv4
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* pseudofilesystem, which provides access only to paths leading to each
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* exported filesystem.
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*/
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#define NFSEXP_V4ROOT 0x10000
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/* All flags that we claim to support. (Note we don't support NOACL.) */
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#define NFSEXP_ALLFLAGS 0x1FE7F
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/* The flags that may vary depending on security flavor: */
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#define NFSEXP_SECINFO_FLAGS (NFSEXP_READONLY | NFSEXP_ROOTSQUASH \
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| NFSEXP_ALLSQUASH \
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| NFSEXP_INSECURE_PORT)
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#endif /* _UAPINFSD_EXPORT_H */
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