[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>

fs/nfs/dir.c

@@ -843,7 +843,7 @@ static void nfs_dentry_iput(struct dentry *dentry, struct inode *inode)
 	nfs_inode_return_delegation(inode);
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
 		lock_kernel();
-		inode->i_nlink--;
+		drop_nlink(inode);
 		nfs_complete_unlink(dentry);
 		unlock_kernel();
 	}
@@ -1401,7 +1401,7 @@ static int nfs_safe_remove(struct dentry *dentry)
 		error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
 		/* The VFS may want to delete this inode */
 		if (error == 0)
-			inode->i_nlink--;
+			drop_nlink(inode);
 		nfs_mark_for_revalidate(inode);
 		nfs_end_data_update(inode);
 	} else
@@ -1639,7 +1639,7 @@ static int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 			goto out;
 		}
 	} else
-		new_inode->i_nlink--;
+		drop_nlink(new_inode);
 
 go_ahead:
 	/*