On Thu, 16 Aug 2007 22:20:06 +0400 Alex Tomas <alex@xxxxxxxxxxxxx> wrote: > Andrew Morton wrote: > >>> But under this proposal, t_sync_datalist just gets removed: the new > >>> ordered-data mode _only_ need to do the sb->inode->page walk. So if I'm > >>> understanding you, the way in which we'd handle any such race is to make > >>> kjournald's writeback of the dirty pages block in lock_page(). Once it > >>> gets the page lock it can look to see if some other thread has mapped the > >>> page to disk. > >> if I'm right holding number of pages locked, then they won't be locked, but > >> writeback. of course kjournald can block on writeback as well, but how does > >> it find pages with *newly allocated* blocks only? > > > > I don't think we'd want kjournald to do that. Even if a page was dirtied > > by an overwrite, we'd want to write it back during commit, just from a > > quality-of-implementation point of view. If we were to leave these pages > > unwritten during commit then a post-recovery file could have a mix of > > up-to-five-second-old data and up-to-30-seconds-old data. > > trying to implement this I've got to think that there is one significant > difference between t_sync_datalist and sb->inode->page walk: t_sync_datalist > is per-transaction. IOW, it doesn't change once transaction is closed. in > contrast, nothing (currently) would prevent others to modify pages while > commit is in progress. That can happen at present - there's nothing to stop a process from modifying a page which is undergoing ordered-data commit-time writeout. - 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
