Name: File Logging Patch
Status: Untested
Signed-off-by: Rusty Russell <rusty@rustcorp.com>

Tridge and I were discussing this a while back: a method of keeping a
record of all changes to files on a mount point, using a finite amount
of room.  Here's my attempt to implement it.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .8843-linux-2.6.9-rc1-bk9/fs/filetrack.c .8843-linux-2.6.9-rc1-bk9.updated/fs/filetrack.c
--- .8843-linux-2.6.9-rc1-bk9/fs/filetrack.c	1970-01-01 10:00:00.000000000 +1000
+++ .8843-linux-2.6.9-rc1-bk9.updated/fs/filetrack.c	2004-09-06 18:41:52.000000000 +1000
@@ -0,0 +1,27 @@
+#include <linux/filetracker.h>
+
+#define TF_DELETED 0x01
+#define TF_ADDED   0x02
+#define TF_WRITTEN 0x04
+
+struct tracked_file
+{
+	struct dentry *me;
+	int flags;
+	int cost;
+};
+
+
+
+void filetrack_delete(struct dentry *dentry)
+{
+}
+
+void filetrack_add(struct dentry *dentry)
+{
+	
+}
+
+void filetrack_write(struct dentry *dentry)
+{
+}
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .8843-linux-2.6.9-rc1-bk9/fs/namei.c .8843-linux-2.6.9-rc1-bk9.updated/fs/namei.c
--- .8843-linux-2.6.9-rc1-bk9/fs/namei.c	2004-09-03 09:31:01.000000000 +1000
+++ .8843-linux-2.6.9-rc1-bk9.updated/fs/namei.c	2004-09-03 14:57:24.000000000 +1000
@@ -1227,6 +1227,7 @@ int vfs_create(struct inode *dir, struct
 	if (!error) {
 		inode_dir_notify(dir, DN_CREATE);
 		security_inode_post_create(dir, dentry, mode);
+		filetrack_add(dentry);
 	}
 	return error;
 }
@@ -2126,6 +2127,8 @@ int vfs_rename(struct inode *old_dir, st
 			inode_dir_notify(old_dir, DN_DELETE);
 			inode_dir_notify(new_dir, DN_CREATE);
 		}
+		filetrack_delete(old_dentry);
+		filetrack_add(new_dentry);
 	}
 	return error;
 }
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .8843-linux-2.6.9-rc1-bk9/fs/read_write.c .8843-linux-2.6.9-rc1-bk9.updated/fs/read_write.c
--- .8843-linux-2.6.9-rc1-bk9/fs/read_write.c	2004-08-16 10:16:33.000000000 +1000
+++ .8843-linux-2.6.9-rc1-bk9.updated/fs/read_write.c	2004-09-03 14:58:33.000000000 +1000
@@ -260,8 +260,10 @@ ssize_t vfs_write(struct file *file, con
 				ret = file->f_op->write(file, buf, count, pos);
 			else
 				ret = do_sync_write(file, buf, count, pos);
-			if (ret > 0)
+			if (ret > 0) {
 				dnotify_parent(file->f_dentry, DN_MODIFY);
+				filetrack_write(file->f_dentry);
+			}
 		}
 	}
 
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .8843-linux-2.6.9-rc1-bk9/include/linux/filetrack.h .8843-linux-2.6.9-rc1-bk9.updated/include/linux/filetrack.h
--- .8843-linux-2.6.9-rc1-bk9/include/linux/filetrack.h	1970-01-01 10:00:00.000000000 +1000
+++ .8843-linux-2.6.9-rc1-bk9.updated/include/linux/filetrack.h	2004-09-03 14:52:42.000000000 +1000
@@ -0,0 +1,20 @@
+#ifndef _LINUX_FILETRACKING_H
+#define _LINUX_FILETRACKING_H
+
+#include <linux/config.h>
+
+#ifdef CONFIG_FILETRACKING
+void filetrack_delete(struct dentry *dentry);
+void filetrack_add(struct dentry *dentry);
+void filetrack_write(struct dentry *dentry);
+#else
+static inline void filetrack_delete(struct dentry *dentry)
+{
+}
+static inline void filetrack_add(struct dentry *dentry)
+{
+}
+static inline void filetrack_write(struct dentry *dentry)
+{
+}
+#endif /* _LINUX_FILETRACKING_H */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .8843-linux-2.6.9-rc1-bk9/mm/mmap.c .8843-linux-2.6.9-rc1-bk9.updated/mm/mmap.c
--- .8843-linux-2.6.9-rc1-bk9/mm/mmap.c	2004-09-03 09:31:09.000000000 +1000
+++ .8843-linux-2.6.9-rc1-bk9.updated/mm/mmap.c	2004-09-03 15:04:43.000000000 +1000
@@ -1587,6 +1587,10 @@ detach_vmas_to_be_unmapped(struct mm_str
 
 	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
 	do {
+		/* For want of a good time, we mark "write" at munmap. */
+		if (vma->vm_file && (vma->vm_flags & VM_WRITE))
+			filetrack_write(vma->vm_file->f_dentry);
+
 		rb_erase(&vma->vm_rb, &mm->mm_rb);
 		mm->map_count--;
 		tail_vma = vma;