On Sep 22, 2008 11:32 +0200, Fr�d�ric Boh� wrote: > Le lundi 22 septembre 2008 à 14:17 +0530, Aneesh Kumar K.V a écrit : > > What you can do is make ext4_group_info generic for both mballoc and > > oldalloc. We can then add bg_flag to the in memory ext4_group_info > > that would indicate whether the group is initialized or not. Here > > initialized for an UNINIT_GROUP indicate we have done > > ext4_init_block_bitmap on the buffer_head. Then > > instead of depending on the buffer_head uptodate flag we can check > > for the ext4_group_info bg_flags and decided whether the block/inode > > bitmap need to be initialized. > > That makes sense ! I agree with you, we need an additional in-memory > flag to know whether buffers are initialized or not. Anyway, making > ext4_group_info generic will lead to unneeded memory consumption for > oldalloc. Maybe a simple independent bits array could do the trick. Is > there any advantage to re-use ext4_group_info ? For ext4 I think 99% of users will use mballoc, and the reduction in code complexity is itself useful. I don't think the in-memory overhead is very much, maybe 1 MB per TB of filesystem space. Also, if you are considering this approach (to initialize the in-memory bitmaps at mount time) they should be written to disk even if unused. Please also consider doing the inode table zeroing at the same time. This would allow uninit_bg to avoid doing it at mke2fs time. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- 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
