Thank you for your reply. > > > > @@ -3700,7 +3701,8 @@ > > start_blk = start >> inode->i_sb->s_blocksize_bits; > > - len_blks = len >> inode->i_sb->s_blocksize_bits; > > + end_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits; > > + len_blks = end_blk - start_blk + 1; > > I don't think this is quite correct either. For example, if blocksize > is 1024 > and start is 1023 (start_blk = 0) and len is 2 (end = 1024, end_blk = > 1) then > len_blks = 2 which is too much. I think that len_blks = 2 is the correct value, because the requested region extends into 2 blocks (namely 0 and 1). If both blocks are in two separate extents, then ext4_ext_walk_space should report 2 extents. (If it's the same extent, only 1 will be reported anyways) > I think the right calculation here is: > > end_blk = (start + len + inode->i_sb->s_blocksize - 1) >> > inode->i_sb->s_blocksize_bits; > len_blks = end_blk - start_blk; > This is exactly the same (provided that len > 0). You can convince yourself easily that ((blocksize + x) >> blocksize_bits == x >> blocksize_bits + 1) for any positive x, because the lower bits of blocksize are all 0. (Your calculation would handle the case len == 0 right, if that was allowed.) Regards Leonard -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
