2be417843a
Testing with it, there appears to be a race between Lookup
and VOPs like Setattr-of-size, where Lookup ends up loading
stale attributes (including what might be the wrong file size)
into the NFS vnode's attribute cache.
The race occurs when the modifying VOP (which holds a lock
on the vnode), blocks the acquisition of the vnode in Lookup,
after the RPC (with now potentially stale attributes).
Here's what seems to happen:
Child Parent
does stat(), which does
VOP_LOOKUP(), doing the Lookup
RPC with the directory vnode
locked, acquiring file attributes
valid at this point in time
blocks waiting for locked file does ftruncate(), which
vnode does VOP_SETATTR() of Size,
changing the file's size
while holding an exclusive
lock on the file's vnode
releases the vnode lock
acquires file vnode and fills in
now stale attributes including
the old wrong Size
does a read() which returns
wrong data size
This patch fixes the problem by saving a timestamp in the NFS vnode
in the VOPs that modify the file (Setattr-of-size, Allocate).
Then lookup/readdirplus compares that timestamp with the time just
before starting the RPC after it has acquired the file's vnode.
If the modifying RPC occurred during the Lookup, the attributes
in the RPC reply are discarded, since they might be stale.
With this patch the test program works as expected.
Note that the test program does not fail on a July stable/12,
although this race is in the NFS client code. I suspect a
fairly recent change to the name caching code exposed this
bug.
PR: 259071
Reviewed by: asomers
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D32635
203 lines
7.8 KiB
C
203 lines
7.8 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Rick Macklem at The University of Guelph.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _NFSCLIENT_NFSNODE_H_
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#define _NFSCLIENT_NFSNODE_H_
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#include <sys/_task.h>
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/*
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* Silly rename structure that hangs off the nfsnode until the name
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* can be removed by nfs_inactive()
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*/
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struct sillyrename {
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struct task s_task;
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struct ucred *s_cred;
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struct vnode *s_dvp;
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long s_namlen;
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char s_name[32];
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};
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/*
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* This structure is used to save the logical directory offset to
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* NFS cookie mappings.
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* The mappings are stored in a list headed
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* by n_cookies, as required.
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* There is one mapping for each NFS_DIRBLKSIZ bytes of directory information
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* stored in increasing logical offset byte order.
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*/
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#define NFSNUMCOOKIES 31
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struct nfsdmap {
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LIST_ENTRY(nfsdmap) ndm_list;
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int ndm_eocookie;
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union {
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nfsuint64 ndmu3_cookies[NFSNUMCOOKIES];
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uint64_t ndmu4_cookies[NFSNUMCOOKIES];
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} ndm_un1;
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};
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#define ndm_cookies ndm_un1.ndmu3_cookies
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#define ndm4_cookies ndm_un1.ndmu4_cookies
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struct nfs_accesscache {
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u_int32_t mode; /* ACCESS mode cache */
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uid_t uid; /* credentials having mode */
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time_t stamp; /* mode cache timestamp */
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};
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/*
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* The nfsnode is the nfs equivalent to ufs's inode. Any similarity
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* is purely coincidental.
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* There is a unique nfsnode allocated for each active file,
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* each current directory, each mounted-on file, text file, and the root.
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* An nfsnode is 'named' by its file handle. (nget/nfs_node.c)
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* If this structure exceeds 256 bytes (it is currently 256 using 4.4BSD-Lite
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* type definitions), file handles of > 32 bytes should probably be split out
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* into a separate malloc()'d data structure. (Reduce the size of nfsfh_t by
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* changing the definition in nfsproto.h of NFS_SMALLFH.)
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* NB: Hopefully the current order of the fields is such that everything will
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* be well aligned and, therefore, tightly packed.
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*/
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struct nfsnode {
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struct mtx n_mtx; /* Protects all of these members */
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struct lock n_excl; /* Exclusive helper for shared
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vnode lock */
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u_quad_t n_size; /* Current size of file */
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u_quad_t n_brev; /* Modify rev when cached */
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u_quad_t n_lrev; /* Modify rev for lease */
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struct nfsvattr n_vattr; /* Vnode attribute cache */
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time_t n_attrstamp; /* Attr. cache timestamp */
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struct nfs_accesscache n_accesscache[NFS_ACCESSCACHESIZE];
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struct timespec n_mtime; /* Prev modify time. */
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struct nfsfh *n_fhp; /* NFS File Handle */
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struct vnode *n_vnode; /* associated vnode */
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struct vnode *n_dvp; /* parent vnode */
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struct lockf *n_lockf; /* Locking record of file */
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int n_error; /* Save write error value */
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union {
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struct timespec nf_atim; /* Special file times */
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nfsuint64 nd_cookieverf; /* Cookie verifier (dir only) */
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u_char nd4_cookieverf[NFSX_VERF];
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} n_un1;
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union {
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struct timespec nf_mtim;
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off_t nd_direof; /* Dir. EOF offset cache */
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} n_un2;
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union {
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struct sillyrename *nf_silly; /* Ptr to silly rename struct */
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LIST_HEAD(, nfsdmap) nd_cook; /* cookies */
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} n_un3;
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short n_fhsize; /* size in bytes, of fh */
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u_int32_t n_flag; /* Flag for locking.. */
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int n_directio_opens;
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int n_directio_asyncwr;
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u_int64_t n_change; /* old Change attribute */
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struct nfsv4node *n_v4; /* extra V4 stuff */
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struct ucred *n_writecred; /* Cred. for putpages */
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struct nfsclopen *n_openstateid; /* Cached open stateid */
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struct timespec n_localmodtime; /* Last local modify */
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};
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#define n_atim n_un1.nf_atim
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#define n_mtim n_un2.nf_mtim
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#define n_sillyrename n_un3.nf_silly
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#define n_cookieverf n_un1.nd_cookieverf
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#define n4_cookieverf n_un1.nd4_cookieverf
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#define n_direofoffset n_un2.nd_direof
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#define n_cookies n_un3.nd_cook
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/*
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* Flags for n_flag
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*/
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#define NDIRCOOKIELK 0x00000001 /* Lock to serialize access to directory cookies */
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#define NFSYNCWAIT 0x00000002 /* fsync waiting for all directio async
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writes to drain */
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#define NMODIFIED 0x00000004 /* Might have a modified buffer in bio */
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#define NWRITEERR 0x00000008 /* Flag write errors so close will know */
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#define NCREATED 0x00000010 /* Opened by nfs_create() */
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#define NTRUNCATE 0x00000020 /* Opened by nfs_setattr() */
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#define NSIZECHANGED 0x00000040 /* File size has changed: need cache inval */
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#define NNONCACHE 0x00000080 /* Node marked as noncacheable */
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#define NACC 0x00000100 /* Special file accessed */
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#define NUPD 0x00000200 /* Special file updated */
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#define NCHG 0x00000400 /* Special file times changed */
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#define NDELEGMOD 0x00000800 /* Modified delegation */
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#define NDELEGRECALL 0x00001000 /* Recall in progress */
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#define NREMOVEINPROG 0x00002000 /* Remove in progress */
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#define NREMOVEWANT 0x00004000 /* Want notification that remove is done */
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#define NLOCK 0x00008000 /* Sleep lock the node */
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#define NLOCKWANT 0x00010000 /* Want the sleep lock */
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#define NNOLAYOUT 0x00020000 /* Can't get a layout for this file */
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#define NWRITEOPENED 0x00040000 /* Has been opened for writing */
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#define NHASBEENLOCKED 0x00080000 /* Has been file locked. */
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#define NDSCOMMIT 0x00100000 /* Commit is done via the DS. */
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#define NVNSETSZSKIP 0x00200000 /* Skipped vnode_pager_setsize() */
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#define NMIGHTBELOCKED 0x00400000 /* Might be file locked. */
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/*
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* Convert between nfsnode pointers and vnode pointers
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*/
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#define VTONFS(vp) ((struct nfsnode *)(vp)->v_data)
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#define NFSTOV(np) ((struct vnode *)(np)->n_vnode)
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#define NFS_TIMESPEC_COMPARE(T1, T2) (((T1)->tv_sec != (T2)->tv_sec) || ((T1)->tv_nsec != (T2)->tv_nsec))
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#if defined(_KERNEL)
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/*
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* Prototypes for NFS vnode operations
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*/
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int ncl_getpages(struct vop_getpages_args *);
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int ncl_putpages(struct vop_putpages_args *);
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int ncl_write(struct vop_write_args *);
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int ncl_inactive(struct vop_inactive_args *);
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int ncl_reclaim(struct vop_reclaim_args *);
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/* other stuff */
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int ncl_removeit(struct sillyrename *, struct vnode *);
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int ncl_nget(struct mount *, u_int8_t *, int, struct nfsnode **, int);
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nfsuint64 *ncl_getcookie(struct nfsnode *, off_t, int);
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void ncl_invaldir(struct vnode *);
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bool ncl_excl_start(struct vnode *);
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void ncl_excl_finish(struct vnode *, bool old_lock);
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void ncl_dircookie_lock(struct nfsnode *);
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void ncl_dircookie_unlock(struct nfsnode *);
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#endif /* _KERNEL */
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#endif /* _NFSCLIENT_NFSNODE_H_ */
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