[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>

4 files changed, 15 insertions, 126 deletions

diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index c27f546dd25b..c4d13bf904d2 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -1,7 +1,7 @@
 /*
  * V9FS FID Management
  *
- *  Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
+ *  Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
  *
  *  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, struct dentry *dentry)
         }
 
         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 v9fs_session_info *v9ses, int fid)
         new->rdir_fcall = NULL;
         INIT_LIST_HEAD(&new->list);
 
-                return new;
+        return new;
 }
 
 /**
@@ -104,75 +103,13 @@ void v9fs_fid_destroy(struct v9fs_fid *fid)
 }
 
 /**
- * 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 dentry *dentry)
                 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
index 7ccf0d064e25..1fc2dd08d75a 100644
--- 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
index ef3386549140..61352491ba36 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -397,6 +397,7 @@ v9fs_session_init(struct v9fs_session_info *v9ses,
         }
 
         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
index 2dd806dac9f1..12c9cc926b71 100644
--- 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 *dentry)
 }
 
 struct dentry_operations v9fs_dentry_operations = {
-        .d_revalidate = v9fs_dentry_validate,
+        .d_delete = v9fs_dentry_delete,
         .d_release = v9fs_dentry_release,
 };