[PATCH] r/o bind mounts: monitor zeroing of i_nlink

Some filesystems, instead of simply decrementing i_nlink, simply zero it
during an unlink operation.  We need to catch these in addition to the
decrement operations.
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/autofs4/root.c

@@ -638,7 +638,7 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
 	dput(ino->dentry);
 
 	dentry->d_inode->i_size = 0;
-	dentry->d_inode->i_nlink = 0;
+	clear_nlink(dentry->d_inode);
 
 	dir->i_mtime = CURRENT_TIME;
 
@@ -673,7 +673,7 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
 	}
 	dput(ino->dentry);
 	dentry->d_inode->i_size = 0;
-	dentry->d_inode->i_nlink = 0;
+	clear_nlink(dentry->d_inode);
 
 	if (dir->i_nlink)
 		drop_nlink(dir);

fs/cifs/inode.c

@@ -818,7 +818,7 @@ int cifs_rmdir(struct inode *inode, struct dentry *direntry)
 	if (!rc) {
 		drop_nlink(inode);
 		i_size_write(direntry->d_inode,0);
-		direntry->d_inode->i_nlink = 0;
+		clear_nlink(direntry->d_inode);
 	}
 
 	cifsInode = CIFS_I(direntry->d_inode);

fs/ext3/namei.c

@@ -2045,7 +2045,7 @@ static int ext3_rmdir (struct inode * dir, struct dentry *dentry)
 			      "empty directory has nlink!=2 (%d)",
 			      inode->i_nlink);
 	inode->i_version++;
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	/* There's no need to set i_disksize: the fact that i_nlink is
 	 * zero will ensure that the right thing happens during any
 	 * recovery. */

fs/fuse/dir.c

@@ -508,7 +508,7 @@ static int fuse_unlink(struct inode *dir, struct dentry *entry)
 		/* Set nlink to zero so the inode can be cleared, if
                    the inode does have more links this will be
                    discovered at the next lookup/getattr */
-		inode->i_nlink = 0;
+		clear_nlink(inode);
 		fuse_invalidate_attr(inode);
 		fuse_invalidate_attr(dir);
 		fuse_invalidate_entry_cache(entry);
@@ -534,7 +534,7 @@ static int fuse_rmdir(struct inode *dir, struct dentry *entry)
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
 	if (!err) {
-		entry->d_inode->i_nlink = 0;
+		clear_nlink(entry->d_inode);
 		fuse_invalidate_attr(dir);
 		fuse_invalidate_entry_cache(entry);
 	} else if (err == -EINTR)

fs/hfs/dir.c

@@ -273,7 +273,7 @@ static int hfs_rmdir(struct inode *dir, struct dentry *dentry)
 	res = hfs_cat_delete(inode->i_ino, dir, &dentry->d_name);
 	if (res)
 		return res;
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_ctime = CURRENT_TIME_SEC;
 	hfs_delete_inode(inode);
 	mark_inode_dirty(inode);

fs/hfsplus/dir.c

@@ -348,7 +348,7 @@ static int hfsplus_unlink(struct inode *dir, struct dentry *dentry)
 		} else
 			inode->i_flags |= S_DEAD;
 	} else
-		inode->i_nlink = 0;
+		clear_nlink(inode);
 	inode->i_ctime = CURRENT_TIME_SEC;
 	mark_inode_dirty(inode);
 
@@ -387,7 +387,7 @@ static int hfsplus_rmdir(struct inode *dir, struct dentry *dentry)
 	res = hfsplus_delete_cat(inode->i_ino, dir, &dentry->d_name);
 	if (res)
 		return res;
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_ctime = CURRENT_TIME_SEC;
 	hfsplus_delete_inode(inode);
 	mark_inode_dirty(inode);

fs/hpfs/namei.c

@@ -495,7 +495,7 @@ static int hpfs_rmdir(struct inode *dir, struct dentry *dentry)
 		break;
 	default:
 		drop_nlink(dir);
-		inode->i_nlink = 0;
+		clear_nlink(inode);
 		err = 0;
 	}
 	goto out;
@@ -590,7 +590,7 @@ static int hpfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 		int r;
 		if ((r = hpfs_remove_dirent(old_dir, dno, dep, &qbh, 1)) != 2) {
 			if ((nde = map_dirent(new_dir, hpfs_i(new_dir)->i_dno, (char *)new_name, new_len, NULL, &qbh1))) {
-				new_inode->i_nlink = 0;
+				clear_nlink(new_inode);
 				copy_de(nde, &de);
 				memcpy(nde->name, new_name, new_len);
 				hpfs_mark_4buffers_dirty(&qbh1);

fs/jfs/namei.c

@@ -414,7 +414,7 @@ static int jfs_rmdir(struct inode *dip, struct dentry *dentry)
 	JFS_IP(ip)->acl.flag = 0;
 
 	/* mark the target directory as deleted */
-	ip->i_nlink = 0;
+	clear_nlink(ip);
 	mark_inode_dirty(ip);
 
 	rc = txCommit(tid, 2, &iplist[0], 0);

fs/msdos/namei.c

@@ -345,7 +345,7 @@ static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
 		goto out;
 	drop_nlink(dir);
 
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_ctime = CURRENT_TIME_SEC;
 	fat_detach(inode);
 out:
@@ -430,7 +430,7 @@ static int msdos_unlink(struct inode *dir, struct dentry *dentry)
 	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
 	if (err)
 		goto out;
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_ctime = CURRENT_TIME_SEC;
 	fat_detach(inode);
 out:

fs/nfs/dir.c

@@ -1286,7 +1286,7 @@ static int nfs_rmdir(struct inode *dir, struct dentry *dentry)
 	error = NFS_PROTO(dir)->rmdir(dir, &dentry->d_name);
 	/* Ensure the VFS deletes this inode */
 	if (error == 0 && dentry->d_inode != NULL)
-		dentry->d_inode->i_nlink = 0;
+		clear_nlink(dentry->d_inode);
 	nfs_end_data_update(dir);
 	unlock_kernel();
 

fs/qnx4/namei.c

@@ -186,7 +186,7 @@ int qnx4_rmdir(struct inode *dir, struct dentry *dentry)
 	memset(de->di_fname, 0, sizeof de->di_fname);
 	de->di_mode = 0;
 	mark_buffer_dirty(bh);
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	mark_inode_dirty(inode);
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME_SEC;
 	inode_dec_link_count(dir);

fs/reiserfs/namei.c

@@ -913,7 +913,7 @@ static int reiserfs_rmdir(struct inode *dir, struct dentry *dentry)
 		reiserfs_warning(inode->i_sb, "%s: empty directory has nlink "
 				 "!= 2 (%d)", __FUNCTION__, inode->i_nlink);
 
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME_SEC;
 	reiserfs_update_sd(&th, inode);
 
@@ -1473,7 +1473,7 @@ static int reiserfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (new_dentry_inode) {
 		// adjust link number of the victim
 		if (S_ISDIR(new_dentry_inode->i_mode)) {
-			new_dentry_inode->i_nlink = 0;
+			clear_nlink(new_dentry_inode);
 		} else {
 			drop_nlink(new_dentry_inode);
 		}

fs/udf/namei.c

@@ -876,7 +876,7 @@ static int udf_rmdir(struct inode * dir, struct dentry * dentry)
 		udf_warning(inode->i_sb, "udf_rmdir",
 			"empty directory has nlink != 2 (%d)",
 			inode->i_nlink);
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_size = 0;
 	inode_dec_link_count(inode);
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_fs_time(dir->i_sb);

fs/vfat/namei.c

@@ -784,7 +784,7 @@ static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
 		goto out;
 	drop_nlink(dir);
 
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
 	fat_detach(inode);
 out:
@@ -808,7 +808,7 @@ static int vfat_unlink(struct inode *dir, struct dentry *dentry)
 	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
 	if (err)
 		goto out;
-	inode->i_nlink = 0;
+	clear_nlink(inode);
 	inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
 	fat_detach(inode);
 out:

include/linux/fs.h

@@ -1235,6 +1235,11 @@ static inline void drop_nlink(struct inode *inode)
 	inode->i_nlink--;
 }
 
+static inline void clear_nlink(struct inode *inode)
+{
+	inode->i_nlink = 0;
+}
+
 static inline void inode_dec_link_count(struct inode *inode)
 {
 	drop_nlink(inode);