Subject: [PATCH] v9fs: fix fid management
From: Eric Van Hensbergen <[email protected]>
Date: 1140666276 -0600
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 <[email protected]>
---
fs/9p/fid.c | 94 +++-------------------------------------------------
fs/9p/fid.h | 1 -
fs/9p/v9fs.c | 1 +
fs/9p/vfs_dentry.c | 45 ++++---------------------
4 files changed, 15 insertions(+), 126 deletions(-)
255909b76466561a6626bcd49a7676ff5c5aab42
diff --git a/fs/9p/fid.c b/fs/9p/fid.c
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -1,7 +1,7 @@
/*
* V9FS FID Management
*
- * Copyright (C) 2005 by Eric Van Hensbergen <[email protected]>
+ * Copyright (C) 2005, 2006 by Eric Van Hensbergen <[email protected]>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -57,7 +57,6 @@ int v9fs_fid_insert(struct v9fs_fid *fid
}
fid->uid = current->uid;
- fid->pid = current->pid;
list_add(&fid->list, fid_list);
return 0;
}
@@ -88,7 +87,7 @@ struct v9fs_fid *v9fs_fid_create(struct
new->rdir_fcall = NULL;
INIT_LIST_HEAD(&new->list);
- return new;
+ return new;
}
/**
@@ -104,75 +103,13 @@ void v9fs_fid_destroy(struct v9fs_fid *f
}
/**
- * v9fs_fid_walk_up - walks from the process current directory
- * up to the specified dentry.
- */
-static struct v9fs_fid *v9fs_fid_walk_up(struct dentry *dentry)
-{
- int fidnum, cfidnum, err;
- struct v9fs_fid *cfid, *fid;
- struct dentry *cde;
- struct v9fs_session_info *v9ses;
-
- v9ses = v9fs_inode2v9ses(current->fs->pwd->d_inode);
- cfid = v9fs_fid_lookup(current->fs->pwd);
- if (cfid == NULL) {
- dprintk(DEBUG_ERROR, "process cwd doesn't have a fid\n");
- return ERR_PTR(-ENOENT);
- }
-
- cfidnum = cfid->fid;
- cde = current->fs->pwd;
- /* TODO: take advantage of multiwalk */
-
- fidnum = v9fs_get_idpool(&v9ses->fidpool);
- if (fidnum < 0) {
- dprintk(DEBUG_ERROR, "could not get a new fid num\n");
- err = -ENOENT;
- goto clunk_fid;
- }
-
- while (cde != dentry) {
- if (cde == cde->d_parent) {
- dprintk(DEBUG_ERROR, "can't find dentry\n");
- err = -ENOENT;
- goto clunk_fid;
- }
-
- err = v9fs_t_walk(v9ses, cfidnum, fidnum, "..", NULL);
- if (err < 0) {
- dprintk(DEBUG_ERROR, "problem walking to parent\n");
- goto clunk_fid;
- }
-
- cfidnum = fidnum;
- cde = cde->d_parent;
- }
-
- fid = v9fs_fid_create(v9ses, fidnum);
- if (fid) {
- err = v9fs_fid_insert(fid, dentry);
- if (err < 0) {
- kfree(fid);
- goto clunk_fid;
- }
- }
-
- return fid;
-
-clunk_fid:
- v9fs_t_clunk(v9ses, fidnum);
- return ERR_PTR(err);
-}
-
-/**
* v9fs_fid_lookup - retrieve the right fid from a particular dentry
* @dentry: dentry to look for fid in
* @type: intent of lookup (operation or traversal)
*
- * search list of fids associated with a dentry for a fid with a matching
- * thread id or uid. If that fails, look up the dentry's parents to see if you
- * can find a matching fid.
+ * find a fid in the dentry
+ *
+ * TODO: only match fids that have the same uid as current user
*
*/
@@ -187,26 +124,7 @@ struct v9fs_fid *v9fs_fid_lookup(struct
return_fid = list_entry(fid_list->next, struct v9fs_fid, list);
if (!return_fid) {
- struct dentry *par = current->fs->pwd->d_parent;
- int count = 1;
- while (par != NULL) {
- if (par == dentry)
- break;
- count++;
- if (par == par->d_parent) {
- dprintk(DEBUG_ERROR,
- "got to root without finding dentry\n");
- break;
- }
- par = par->d_parent;
- }
-
-/* XXX - there may be some duplication we can get rid of */
- if (par == dentry) {
- return_fid = v9fs_fid_walk_up(dentry);
- if (IS_ERR(return_fid))
- return_fid = NULL;
- }
+ dprintk(DEBUG_ERROR, "Couldn't find a fid in dentry\n");
}
return return_fid;
diff --git a/fs/9p/fid.h b/fs/9p/fid.h
--- a/fs/9p/fid.h
+++ b/fs/9p/fid.h
@@ -44,7 +44,6 @@ struct v9fs_fid {
struct v9fs_fcall *rdir_fcall;
/* management stuff */
- pid_t pid; /* thread associated with this fid */
uid_t uid; /* user associated with this fid */
/* private data */
diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -397,6 +397,7 @@ v9fs_session_init(struct v9fs_session_in
}
if (v9ses->afid != ~0) {
+ dprintk(DEBUG_ERROR, "afid not equal to ~0\n");
if (v9fs_t_clunk(v9ses, v9ses->afid))
dprintk(DEBUG_ERROR, "clunk failed\n");
}
diff --git a/fs/9p/vfs_dentry.c b/fs/9p/vfs_dentry.c
--- a/fs/9p/vfs_dentry.c
+++ b/fs/9p/vfs_dentry.c
@@ -43,47 +43,18 @@
#include "fid.h"
/**
- * v9fs_dentry_validate - VFS dcache hook to validate cache
- * @dentry: dentry that is being validated
- * @nd: path data
+ * v9fs_dentry_delete - called when dentry refcount equals 0
+ * @dentry: dentry in question
*
- * dcache really shouldn't be used for 9P2000 as at all due to
- * potential attached semantics to directory traversal (walk).
- *
- * FUTURE: look into how to use dcache to allow multi-stage
- * walks in Plan 9 & potential for better dcache operation which
- * would remain valid for Plan 9 semantics. Older versions
- * had validation via stat for those interested. However, since
- * stat has the same approximate overhead as walk there really
- * is no difference. The only improvement would be from a
- * time-decay cache like NFS has and that undermines the
- * synchronous nature of 9P2000.
+ * By returning 1 here we should remove cacheing of unused
+ * dentry components.
*
*/
-static int v9fs_dentry_validate(struct dentry *dentry, struct nameidata *nd)
+int v9fs_dentry_delete(struct dentry *dentry)
{
- struct dentry *dc = current->fs->pwd;
-
- dprintk(DEBUG_VFS, "dentry: %s (%p)\n", dentry->d_iname, dentry);
- if (v9fs_fid_lookup(dentry)) {
- dprintk(DEBUG_VFS, "VALID\n");
- return 1;
- }
-
- while (dc != NULL) {
- if (dc == dentry) {
- dprintk(DEBUG_VFS, "VALID\n");
- return 1;
- }
- if (dc == dc->d_parent)
- break;
-
- dc = dc->d_parent;
- }
-
- dprintk(DEBUG_VFS, "INVALID\n");
- return 0;
+ dprintk(DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
+ return 1;
}
/**
@@ -118,6 +89,6 @@ void v9fs_dentry_release(struct dentry *
}
struct dentry_operations v9fs_dentry_operations = {
- .d_revalidate = v9fs_dentry_validate,
+ .d_delete = v9fs_dentry_delete,
.d_release = v9fs_dentry_release,
};
-
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