On May 17, 2008 09:43 -0400, Theodore Ts'o wrote: > On Fri, May 16, 2008 at 05:35:52PM -0700, Andrew Morton wrote: > > Journal wrapping could cause the commit block to get written before its > > data blocks. We could improve that by changing the journal layout a bit: > > wrap the entire commit rather than just its tail. Such a change might > > be intrusive though. > > Or we backport jbd2's checksum support in the commit block to jbd; > with the checksum support, if the commit block is written out-of-order > with the rest of the blocks in the commit, the commit will simply not > be recognized as valid, and we'll use the previous commit block as the > last valid commit. The jbd2 journal checksum support, along with the 64-bit journal block layout is designed to be 100% compatible with jbd, so it would be trivial to "back port" jbd2. Just copy jbd2 into jbd, and add the option to set (or set by default) the JBD_FEATURE_COMPAT_CHECKSUM feature in the journal. I was going to suggest complete removal of jbd2 at that point, but the ordered-mode rewrite is still pending and should live in ext4 for a reasonably long while before going back to ext3. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
