ext4: convert to mbcache2

The conversion is generally straightforward. The only tricky part is
that xattr block corresponding to found mbcache entry can get freed
before we get buffer lock for that block. So we have to check whether
the entry is still valid after getting buffer lock.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
ext4_xattr_delete_inode(handle_t *handle, struct inode *inode)
{
	struct buffer_head *bh = NULL;

	if (!EXT4_I(inode)->i_file_acl)
		goto cleanup;
	bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
	if (!bh) {
		EXT4_ERROR_INODE(inode, "block %llu read error",
				 EXT4_I(inode)->i_file_acl);
		goto cleanup;
	}
	if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
	    BHDR(bh)->h_blocks != cpu_to_le32(1)) {
		EXT4_ERROR_INODE(inode, "bad block %llu",
				 EXT4_I(inode)->i_file_acl);
		goto cleanup;
	}
	ext4_xattr_release_block(handle, inode, bh);
	EXT4_I(inode)->i_file_acl = 0;

cleanup:
 	brelse(bh);
 }

ext4_xattr_delete_inode(handle_t *handle, struct inode *inode)
{
	struct buffer_head *bh = NULL;

	if (!EXT4_I(inode)->i_file_acl)
		goto cleanup;
	bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
	if (!bh) {
		EXT4_ERROR_INODE(inode, "block %llu read error",
				 EXT4_I(inode)->i_file_acl);
		goto cleanup;
	}
	if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
	    BHDR(bh)->h_blocks != cpu_to_le32(1)) {
		EXT4_ERROR_INODE(inode, "bad block %llu",
				 EXT4_I(inode)->i_file_acl);
		goto cleanup;
	}
	ext4_xattr_release_block(handle, inode, bh);
	EXT4_I(inode)->i_file_acl = 0;

cleanup:
 	brelse(bh);
 }
