Hi, On Wed, 23 Jun 2010 16:23:44 +0900, Jiro SEKIBA wrote: > Hi, > > At Wed, 23 Jun 2010 12:38:56 +0900 (JST), > Ryusuke Konishi wrote: > > > > On Mon, 21 Jun 2010 02:53:10 +0900 (JST), Ryusuke Konishi wrote: > > > On Mon, 21 Jun 2010 01:36:55 +0900, Jiro SEKIBA wrote: > > > > This will sync super blocks in turns instead of syncing duplicate > > > > super blocks at the time. This will help searching valid super root when > > > > super block is written into disk before log is written, which is happen when > > > > barrier-less block devices are unmounted uncleanly. > > > > In the situation, old super block likely points to valid log. > > > > > > > > This patch introduces ns_sbwcount member, which counts how many times super > > > > blocks write back to the disk. Super blocks are asymmetrically synced > > > > based on the counter. > > > > > > > > The patch also introduces new function nilfs_set_log_cursor to advance > > > > log cursor for specified super block. To update both of super block > > > > information, caller of nilfs_commit_super must set the information on both > > > > super blocks. > > > > > > > > Signed-off-by: Jiro SEKIBA <jir@xxxxxxxxx> > > > > > > Thank you! Both patches look good to me. > > > > > > Will queue them up for the next merge window. > > > > > > Thanks, > > > Ryusuke Konishi > > > > Umm, I noticed that nilfs_commit_super is called twice when the > > filesystem is unmounted. This is because nilfs_sync_fs() is called > > just before nilfs_put_super() will do unmount jobs. > > Ahhh, I see the problem. That's right. It would have be the same > checkpoints in case that filesystem is dirty when sync_fs is called. > To slove the problem, I think, it may require controlling swap of > superblocks explicitly. > > How about swaping BEFORE writing the super block instead of AFTER? > > nilfs_prepare_super will take another argument that controls swapping > of super blocks. So caller can decide swap or not. With this feature, > you can prepare super block without swapping in a nilfs_put_super. > Therefore, old super block written before sync_fs called will be preserved > by overwriting the same super block sync_fs wrote back. Sounds reasonable, and more clear to me. Note that sync_fs itself can be called multiple times. The current nilfs_sync_fs implementation is half-baked; it does not handle the syncwait flag argument properly. nilfs_construct_segment() and nilfs_commit_super() should be essentially divided into "commit" and "wait" functions. I also think nilfs_sync_fs does not have to call nilfs_commit_super because the log will be recovered by roll-forwarding even if not updating the log cursor. Anyway, I agree to move the flip operation into nilfs_prepare_super() and to make it selectable with a "flip" flag. It would make things more flexible. > Updating protection period should be took care carefully. > Nhh, then, it can compare the actual checkpoint nubmer of each super blocks > instead of setting sbp[1]'s checkpoint each time. Yes, it is replaceable with the comparison of checkpoint numbers. So, you can move the flip operation into nilfs_prepare_super(). Regards, Ryusuke Konishi -- To unsubscribe from this list: send the line "unsubscribe linux-nilfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
