On 2011年07月29日 21:19, Joel Becker Wrote: > On Fri, Jul 29, 2011 at 03:48:45AM -0600, Andreas Dilger wrote: >> On 2011-07-28, at 4:07 PM, Joel Becker wrote: >>> We use ethernet crc32 in ocfs2. btrfs uses crc32c. Frankly, I >>> could have used crc32c if I'd really thought about the hardware >>> acceleration benefits. I think it's a good idea for ext4. >> >> The problem with crc32[c] is that if you don't have hardware acceleration >> it is terribly slow. > > We find ethernet crc32 just fine in ocfs2. I use the kernel's > implementation, which survives everyone's network traffic, and of course > we added the triggers to jbd2 so we only have to do the calculations on > read and write. > Ext4 supports non-journal mode, and there are a few users (Google, Taobao, etc.). A trigger of jbd2 may not work well for non-journal Ext4 ... And in non-journal mode, there is not copy of any meta data block in jbd2, we need to be more careful in check summing, e.g. inode/block bitmap blocks... >> Yes, it makes sense to just put a "fake" dirent at the end of the leaf block, >> or similar. I don't think it is necessary to modify existing directories or >> extent blocks to add these structures in, if there is no room, but for new >> blocks, or blocks with space it is enough. > > We have tunefs.ocfs2 code to adjust existing directories to add > the trailer. It's not too bad, really. Agree, enable/disable the trailer isn't that difficult. We need more eyes to take care the user space tools. Coly -- 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
