NTFS: Make ntfs_lookup() NFS export safe, i.e. use d_splice_alias(), etc.

fs/ntfs/ChangeLog

@@ -23,6 +23,7 @@ ToDo:
 2.1.7 - WIP
 
 	- Set i_generation in the VFS inode from the seq_no of the NTFS inode.
+	- Make ntfs_lookup() NFS export safe, i.e. use d_splice_alias(), etc.
 
 2.1.6 - Fix minor bug in handling of compressed directories.
 

fs/ntfs/layout.h

@@ -2,7 +2,7 @@
  * layout.h - All NTFS associated on-disk structures. Part of the Linux-NTFS
  *	      project.
  *
- * Copyright (c) 2001-2003 Anton Altaparmakov
+ * Copyright (c) 2001-2004 Anton Altaparmakov
  * Copyright (c) 2002 Richard Russon
  *
  * This program/include file is free software; you can redistribute it and/or

fs/ntfs/namei.c

@@ -2,7 +2,7 @@
  * namei.c - NTFS kernel directory inode operations. Part of the Linux-NTFS
  * 	     project.
  *
- * Copyright (c) 2001-2003 Anton Altaparmakov
+ * Copyright (c) 2001-2004 Anton Altaparmakov
  *
  * This program/include file is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as published
@@ -41,16 +41,17 @@
  * @dir_ino looking for the converted Unicode name. If the name is found in the
  * directory, the corresponding inode is loaded by calling ntfs_iget() on its
  * inode number and the inode is associated with the dentry @dent via a call to
- * d_add().
+ * d_splice_alias().
  *
  * If the name is not found in the directory, a NULL inode is inserted into the
- * dentry @dent. The dentry is then termed a negative dentry.
+ * dentry @dent via a call to d_add(). The dentry is then termed a negative
+ * dentry.
  *
  * Only if an actual error occurs, do we return an error via ERR_PTR().
  *
  * In order to handle the case insensitivity issues of NTFS with regards to the
  * dcache and the dcache requiring only one dentry per directory, we deal with
- * dentry aliases that only differ in case in ->ntfs_lookup() while maintining
+ * dentry aliases that only differ in case in ->ntfs_lookup() while maintaining
  * a case sensitive dcache. This means that we get the full benefit of dcache
  * speed when the file/directory is looked up with the same case as returned by
  * ->ntfs_readdir() but that a lookup for any other case (or for the short file
@@ -70,15 +71,18 @@
  * 1) @dent perfectly matches (i.e. including case) a directory entry with a
  *    file name in the WIN32 or POSIX namespaces. In this case
  *    ntfs_lookup_inode_by_name() will return with name set to NULL and we
- *    just d_add() @dent.
+ *    just d_splice_alias() @dent.
  * 2) @dent matches (not including case) a directory entry with a file name in
  *    the WIN32 namespace. In this case ntfs_lookup_inode_by_name() will return
  *    with name set to point to a kmalloc()ed ntfs_name structure containing
  *    the properly cased little endian Unicode name. We convert the name to the
  *    current NLS code page, search if a dentry with this name already exists
- *    and if so return that instead of @dent. The VFS will then destroy the old
- *    @dent and use the one we returned. If a dentry is not found, we allocate
- *    a new one, d_add() it, and return it as above.
+ *    and if so return that instead of @dent.  At this point things are
+ *    complicated by the possibility of 'disconnected' dentries due to NFS
+ *    which we deal with appropriately (see the code comments).  The VFS will
+ *    then destroy the old @dent and use the one we returned.  If a dentry is
+ *    not found, we allocate a new one, d_splice_alias() it, and return it as
+ *    above.
  * 3) @dent matches either perfectly or not (i.e. we don't care about case) a
  *    directory entry with a file name in the DOS namespace. In this case
  *    ntfs_lookup_inode_by_name() will return with name set to point to a
@@ -120,7 +124,7 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent, st
 					dent_ino == FILE_MFT) {
 				/* Perfect WIN32/POSIX match. -- Case 1. */
 				if (!name) {
-					d_add(dent, dent_inode);
+					d_splice_alias(dent_inode, dent);
 					ntfs_debug("Done.");
 					return NULL;
 				}
@@ -132,7 +136,7 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent, st
 			}
 			ntfs_error(vol->sb, "Found stale reference to inode "
 					"0x%lx (reference sequence number = "
-					"0x%x, inode sequence number = 0x%x, "
+					"0x%x, inode sequence number = 0x%x), "
 					"returning -EIO. Run chkdsk.",
 					dent_ino, MSEQNO(mref),
 					NTFS_I(dent_inode)->seq_no);
@@ -162,7 +166,7 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent, st
 	// TODO: Consider moving this lot to a separate function! (AIA)
 handle_name:
    {
-	struct dentry *real_dent;
+	struct dentry *real_dent, *new_dent;
 	MFT_RECORD *m;
 	attr_search_context *ctx;
 	ntfs_inode *ni = NTFS_I(dent_inode);
@@ -173,8 +177,7 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent, st
 	if (name->type != FILE_NAME_DOS) {			/* Case 2. */
 		nls_name.len = (unsigned)ntfs_ucstonls(vol,
 				(uchar_t*)&name->name, name->len,
-				(unsigned char**)&nls_name.name,
-				name->len * 3 + 1);
+				(unsigned char**)&nls_name.name, 0);
 		kfree(name);
 	} else /* if (name->type == FILE_NAME_DOS) */ {		/* Case 3. */
 		FILE_NAME_ATTR *fn;
@@ -225,8 +228,7 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent, st
 		/* Convert the found WIN32 name to current NLS code page. */
 		nls_name.len = (unsigned)ntfs_ucstonls(vol,
 				(uchar_t*)&fn->file_name, fn->file_name_length,
-				(unsigned char**)&nls_name.name,
-				fn->file_name_length * 3 + 1);
+				(unsigned char**)&nls_name.name, 0);
 
 		put_attr_search_ctx(ctx);
 		unmap_mft_record(ni);
@@ -256,7 +258,7 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent, st
 			err = -ENOMEM;
 			goto err_out;
 		}
-		d_add(real_dent, dent_inode);
+		d_splice_alias(dent_inode, real_dent);
 		return real_dent;
 	}
 	kfree(nls_name.name);
@@ -266,14 +268,54 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent, st
 		/*
 		 * Already have the inode and the dentry attached, decrement
 		 * the reference count to balance the ntfs_iget() we did
-		 * earlier on.
+		 * earlier on.  We found the dentry using d_lookup() so it
+		 * cannot be disconnected and thus we do not need to worry
+		 * about any NFS/disconnectedness issues here.
 		 */
 		iput(dent_inode);
 		return real_dent;
 	}
-	/* Negative dentry: instantiate it. */
-	d_instantiate(real_dent, dent_inode);
-	return real_dent;
+	/*
+	 * Negative dentry: instantiate it unless the inode is a directory and
+	 * has a 'disconnected' dentry (i.e. IS_ROOT and DCACHE_DISCONNECTED),
+	 * in which case d_move() that in place of the found dentry.
+	 */
+	if (!S_ISDIR(dent_inode)) {
+		/* Not a directory; everything is easy. */
+		d_instantiate(real_dent, dent_inode);
+		return real_dent;
+	}
+	spin_lock(&dcache_lock);
+	if (list_empty(&dent_inode->i_dentry)) {
+		/*
+		 * Directory without a 'disconnected' dentry; we need to do
+		 * d_instantiate() by hand because it takes dcache_lock which
+		 * we already hold.
+		 */
+		list_add(&real_dent->d_alias, &dent_inode->i_dentry);
+		real_dent->d_inode = dent_inode;
+		spin_unlock(&dcache_lock);
+		security_d_instantiate(real_dent, dent_inode);
+		return real_dent;
+	}
+	/*
+	 * Directory with a 'disconnected' dentry; get a reference to the
+	 * 'disconnected' dentry.
+	 */
+	new_dent = list_entry(dent_inode->i_dentry.next, struct dentry,
+			d_alias);
+	__dget_locked(new_dent);
+	spin_unlock(&dcache_lock);
+	/* Do security vodoo. */
+	security_d_instantiate(real_dent, dent_inode);
+	/* Move new_dent in place of real_dent. */
+	d_move(new_dent, real_dent);
+	/* Balance the ntfs_iget() we did above. */
+	iput(dent_inode);
+	/* Throw away real_dent. */
+	dput(real_dent);
+	/* Use new_dent as the actual dentry. */
+	return new_dent;
 
 eio_err_out:
 	ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");

fs/ntfs/unistr.c

 /*
  * unistr.c - NTFS Unicode string handling. Part of the Linux-NTFS project.
  *
- * Copyright (c) 2001-2003 Anton Altaparmakov
+ * Copyright (c) 2001-2004 Anton Altaparmakov
  *
  * This program/include file is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as published
@@ -305,8 +305,9 @@ int ntfs_nlstoucs(const ntfs_volume *vol, const char *ins,
  * Convert the input little endian, 2-byte Unicode string @ins, of length
  * @ins_len into the string format dictated by the loaded NLS.
  *
- * If @outs is NULL, this function allocates the string and the caller is
- * responsible for calling kfree(@outs); when finished with it.
+ * If *@outs is NULL, this function allocates the string and the caller is
+ * responsible for calling kfree(*@outs); when finished with it. In this case
+ * @outs_len is ignored and can be 0.
  *
  * On success the function returns the number of bytes written to the output
  * string *@outs (>= 0), not counting the terminating NULL byte. If the output