[PATCH] r/o bind mounts: unlink: monitor i_nlink

When a filesystem decrements i_nlink to zero, it means that a write must be
performed in order to drop the inode from the filesystem.

We're shortly going to have keep filesystems from being remounted r/o between
the time that this i_nlink decrement and that write occurs.

So, add a little helper function to do the decrements.  We'll tie into it in a
bit to note when i_nlink hits zero.

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>
diff --git a/fs/msdos/namei.c b/fs/msdos/namei.c
index d220165..635613f 100644
--- a/fs/msdos/namei.c
+++ b/fs/msdos/namei.c
@@ -343,7 +343,7 @@
 	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
 	if (err)
 		goto out;
-	dir->i_nlink--;
+	drop_nlink(dir);
 
 	inode->i_nlink = 0;
 	inode->i_ctime = CURRENT_TIME_SEC;
@@ -549,7 +549,7 @@
 			if (err)
 				goto error_dotdot;
 		}
-		old_dir->i_nlink--;
+		drop_nlink(old_dir);
 		if (!new_inode)
 			new_dir->i_nlink++;
 	}
@@ -566,10 +566,9 @@
 		mark_inode_dirty(old_dir);
 
 	if (new_inode) {
+		drop_nlink(new_inode);
 		if (is_dir)
-			new_inode->i_nlink -= 2;
-		else
-			new_inode->i_nlink--;
+			drop_nlink(new_inode);
 		new_inode->i_ctime = ts;
 	}
 out: