On Sun, Jul 01, 2007 at 09:48:33AM -0500, Jose R. Santos wrote: > Is your concern due to being unable to find contiguous block in the > case that a bad disk area is in one of the bitmap blocks? One thing we > can do is try to search for another set of contiguous blocks and if we > fail to find one, we can flag the block group and move to an indirect > block approach to allocating the bitmaps. At this point, we do lose > some of the performance benefits of BIG_BG, but we would still be able > to use the block group. Yes, my concern is what we might need to do if for some reason e2fsck needs to reallocate the bitmap blocks. I don't think an indirect block scheme is the right approach, though; we're adding a lot of complexity for a case that probably wouldn't be used but very, very rarely. My proposal (as we discsused) in the call, is to implement BIG_BG as meaning the following: 1) Implementations must understand and use the s_desc_size superblock field to determine whether block group descriptors are the old 32 bytes or the newer 64 bytes format. 2) Implementations must support the newer ext4_group_desc format in particular to support bg_free_blocks_count_hi and bg_free_inodes_count_hi 3) Implementations will relax constraints on where the superblock, bitmaps, and inode tables for a particular block group will be stored. So with that, we can experiment with what size block groups really make sense, versus using the extended metablockgroup idea, or possibly doing both. - Ted - 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
