The new cramfs_unlink function replaces an existing dentry with

a pinned negative dentry in cramfs, so that lookup does not find

it any more.
The readdir function gets changed here to no longer show the file

if a negative dentry exists.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---

 fs/cramfs/inode.c |   27 ++++++++++++++++++++++++++-

 1 files changed, 26 insertions(+), 1 deletions(-)
diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c

index 8aa04d7..6b9f21f 100644

--- a/fs/cramfs/inode.c

+++ b/fs/cramfs/inode.c

@@ -348,12 +348,14 @@ static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 	copied = 0;

 	while (offset < inode->i_size) {

+		struct qstr qstr = { .name = buf, };

 		struct cramfs_inode *de;

 		unsigned long nextoffset;

 		char *name;

 		ino_t ino;

 		mode_t mode;

 		int namelen, error;

+		struct dentry *dentry;
 		mutex_lock(&read_mutex);

 		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);

@@ -379,7 +381,15 @@ static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)

 				break;

 			namelen--;

 		}

-		error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);

+		qstr.len = namelen;

+		dentry = d_hash_and_lookup(filp->f_path.dentry, &qstr);

+

+		error = 0;

+		if (!dentry || (dentry->d_inode))

+				error = filldir(dirent, buf, namelen, offset,

+					ino, mode >> 12);

+

+		dput(dentry);

 		if (error)

 			break;
@@ -391,6 +401,19 @@ static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)

 	return 0;

 }
+int cramfs_unlink(struct inode *dir, struct dentry *dentry)

+{

+	struct inode *inode = dentry->d_inode;

+	struct dentry *new;

+

+	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;

+	drop_nlink(inode);

+	new = d_alloc(dentry->d_parent, &dentry->d_name);

+	d_add(new, NULL);

+

+	dget(dentry);

+	return 0;

+}

 /*

  * Lookup and fill in the inode data..

  */

@@ -512,...
[ message continues ]

How is the negative dentry dropped on umount?  Looks like we want a

per-sb list to put them on.  Then we can walk it and dput each one at
Jörn
--

"[One] doesn't need to know [...] how to cause a headache in order

to take an aspirin."

-- Scott Culp, Manager of the Microsoft Security Response Center, 2001

--

Good point. I think ramfs does exactly that, using kill_litter_super.

I haven't tested unmount so far, and should probably do something like

that in cramfs_put_super.
	Arnd <><

--