>>>>> Mingming Cao (MC) writes: MC> Hi, Amit, MC> Have you looked at ext4_ext_walk_space()? It calculate the right MC> extent length to allocate to avoid overlap before calling block MC> allocation callback function is called. well, it doesn't use cache. MC> What if the start logical block of the exisitng extent is 0 and there MC> is overlap? I think that is possible. For example, the exisitng extent MC> is (0,100) and you want to insert new extent (0,500), this will MC> certainly fail to report the overlap. I think this situation must not happen in the first place. get_blocks() should first find existing blocks and return them (0,100), subsequent get_blocks() should be called for the following blocks (100,500) and handle them properly. MC> Since this overlap check function is called inside MC> ext4_ext_insert_extent(), I think this function should check for all MC> kinds of overlaps. Here you only check if the new extent is overlap MC> with the next extent. Looking at ext4_ext_walk_space(), there are MC> total three kinds of overlaps: MC> 1) righ port of new extent overlap with path->p_ext, MC> 2) left port of new extent overlap with path->p_ext MC> 2) right port of new extent overlap with next extent MC> I think we are almost repeating the same logic in MC> ext4_ext_walk_space() here. I tend to agree. thanks, Alex - 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
