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[PATCH] v9fs: simplify fid mapping
v9fs has been plagued by an over-complicated approach trying to map Linux dentry semantics to Plan 9 fid semantics. Our previous approach called for aggressive flushing of the dcache resulting in several problems (including wierd cwd behavior when running /bin/pwd). This patch dramatically simplifies our handling of this fid management. Fids will not be clunked as promptly, but the new approach is more functionally correct. We now clunk un-open fids only when their dentry ref_count reaches 0 (and d_delete is called). Another simplification is we no longer seek to match fids to the process-id or uid of the action initiator. The uid-matching will need to be revisited when we fix the security model. Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Eric Van Hensbergen
Linus Torvalds
parent
74b8054c73
commit
46f6dac259
94
fs/9p/fid.c
94
fs/9p/fid.c
@ -1,7 +1,7 @@
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/*
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* V9FS FID Management
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*
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* Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
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* Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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@ -57,7 +57,6 @@ int v9fs_fid_insert(struct v9fs_fid *fid, struct dentry *dentry)
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}
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fid->uid = current->uid;
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fid->pid = current->pid;
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list_add(&fid->list, fid_list);
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return 0;
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}
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@ -88,7 +87,7 @@ struct v9fs_fid *v9fs_fid_create(struct v9fs_session_info *v9ses, int fid)
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new->rdir_fcall = NULL;
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INIT_LIST_HEAD(&new->list);
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return new;
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return new;
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}
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/**
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@ -103,76 +102,14 @@ void v9fs_fid_destroy(struct v9fs_fid *fid)
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kfree(fid);
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}
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/**
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* v9fs_fid_walk_up - walks from the process current directory
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* up to the specified dentry.
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*/
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static struct v9fs_fid *v9fs_fid_walk_up(struct dentry *dentry)
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{
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int fidnum, cfidnum, err;
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struct v9fs_fid *cfid, *fid;
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struct dentry *cde;
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struct v9fs_session_info *v9ses;
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v9ses = v9fs_inode2v9ses(current->fs->pwd->d_inode);
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cfid = v9fs_fid_lookup(current->fs->pwd);
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if (cfid == NULL) {
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dprintk(DEBUG_ERROR, "process cwd doesn't have a fid\n");
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return ERR_PTR(-ENOENT);
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}
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cfidnum = cfid->fid;
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cde = current->fs->pwd;
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/* TODO: take advantage of multiwalk */
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fidnum = v9fs_get_idpool(&v9ses->fidpool);
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if (fidnum < 0) {
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dprintk(DEBUG_ERROR, "could not get a new fid num\n");
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err = -ENOENT;
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goto clunk_fid;
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}
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while (cde != dentry) {
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if (cde == cde->d_parent) {
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dprintk(DEBUG_ERROR, "can't find dentry\n");
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err = -ENOENT;
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goto clunk_fid;
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}
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err = v9fs_t_walk(v9ses, cfidnum, fidnum, "..", NULL);
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if (err < 0) {
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dprintk(DEBUG_ERROR, "problem walking to parent\n");
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goto clunk_fid;
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}
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cfidnum = fidnum;
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cde = cde->d_parent;
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}
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fid = v9fs_fid_create(v9ses, fidnum);
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if (fid) {
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err = v9fs_fid_insert(fid, dentry);
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if (err < 0) {
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kfree(fid);
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goto clunk_fid;
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}
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}
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return fid;
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clunk_fid:
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v9fs_t_clunk(v9ses, fidnum);
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return ERR_PTR(err);
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}
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/**
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* v9fs_fid_lookup - retrieve the right fid from a particular dentry
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* @dentry: dentry to look for fid in
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* @type: intent of lookup (operation or traversal)
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*
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* search list of fids associated with a dentry for a fid with a matching
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* thread id or uid. If that fails, look up the dentry's parents to see if you
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* can find a matching fid.
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* find a fid in the dentry
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*
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* TODO: only match fids that have the same uid as current user
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*
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*/
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@ -187,26 +124,7 @@ struct v9fs_fid *v9fs_fid_lookup(struct dentry *dentry)
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return_fid = list_entry(fid_list->next, struct v9fs_fid, list);
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if (!return_fid) {
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struct dentry *par = current->fs->pwd->d_parent;
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int count = 1;
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while (par != NULL) {
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if (par == dentry)
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break;
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count++;
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if (par == par->d_parent) {
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dprintk(DEBUG_ERROR,
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"got to root without finding dentry\n");
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break;
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}
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par = par->d_parent;
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}
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/* XXX - there may be some duplication we can get rid of */
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if (par == dentry) {
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return_fid = v9fs_fid_walk_up(dentry);
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if (IS_ERR(return_fid))
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return_fid = NULL;
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}
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dprintk(DEBUG_ERROR, "Couldn't find a fid in dentry\n");
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}
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return return_fid;
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@ -44,7 +44,6 @@ struct v9fs_fid {
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struct v9fs_fcall *rdir_fcall;
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/* management stuff */
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pid_t pid; /* thread associated with this fid */
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uid_t uid; /* user associated with this fid */
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/* private data */
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@ -397,6 +397,7 @@ v9fs_session_init(struct v9fs_session_info *v9ses,
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}
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if (v9ses->afid != ~0) {
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dprintk(DEBUG_ERROR, "afid not equal to ~0\n");
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if (v9fs_t_clunk(v9ses, v9ses->afid))
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dprintk(DEBUG_ERROR, "clunk failed\n");
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}
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@ -43,47 +43,18 @@
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#include "fid.h"
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/**
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* v9fs_dentry_validate - VFS dcache hook to validate cache
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* @dentry: dentry that is being validated
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* @nd: path data
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* v9fs_dentry_delete - called when dentry refcount equals 0
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* @dentry: dentry in question
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*
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* dcache really shouldn't be used for 9P2000 as at all due to
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* potential attached semantics to directory traversal (walk).
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*
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* FUTURE: look into how to use dcache to allow multi-stage
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* walks in Plan 9 & potential for better dcache operation which
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* would remain valid for Plan 9 semantics. Older versions
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* had validation via stat for those interested. However, since
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* stat has the same approximate overhead as walk there really
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* is no difference. The only improvement would be from a
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* time-decay cache like NFS has and that undermines the
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* synchronous nature of 9P2000.
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* By returning 1 here we should remove cacheing of unused
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* dentry components.
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*
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*/
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static int v9fs_dentry_validate(struct dentry *dentry, struct nameidata *nd)
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int v9fs_dentry_delete(struct dentry *dentry)
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{
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struct dentry *dc = current->fs->pwd;
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dprintk(DEBUG_VFS, "dentry: %s (%p)\n", dentry->d_iname, dentry);
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if (v9fs_fid_lookup(dentry)) {
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dprintk(DEBUG_VFS, "VALID\n");
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return 1;
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}
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while (dc != NULL) {
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if (dc == dentry) {
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dprintk(DEBUG_VFS, "VALID\n");
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return 1;
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}
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if (dc == dc->d_parent)
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break;
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dc = dc->d_parent;
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}
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dprintk(DEBUG_VFS, "INVALID\n");
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return 0;
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dprintk(DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
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return 1;
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}
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/**
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@ -118,6 +89,6 @@ void v9fs_dentry_release(struct dentry *dentry)
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}
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struct dentry_operations v9fs_dentry_operations = {
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.d_revalidate = v9fs_dentry_validate,
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.d_delete = v9fs_dentry_delete,
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.d_release = v9fs_dentry_release,
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};
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