Hi folks, This is a series I posted months ago with the first thinspace filesystem support. There was no comments on any of these patches because all the heat and light got focussed on the growfs API. I'm posting this separately to avoid that problem again.... Anyway, the core of this change is to make the growfs code much simpler to extend. Most of the code that does structure initialisation is cookie-cutter code and it's whacked into one great big function. This patch set splits it up into separate functions and uses common helper functions where possible. The different structures and their initialisation definitions are now held in a table, so when we add new stuctures or modify existing structures it's a simple and isolate change. The reworked initialisation code is suitable for moving to libxfs and converting mkfs.xfs to use it for the initial formatting of the filesystem. This will take more work to acheive, so this patch set stops short of moving the code to libxfs. The other changes to the growfs code in this patchset also isolate separate parts of the growfs functionality, such as updating the secondary superblocks and changing imaxpct. This makes adding thinspace functionality to growfs much easier. Finally, there are optimisations to make a large AG count growfs much faster. Instead of initialising and writing headers one at a time synchronously, they are added to a delwri buffer list and written in bulk and asynchronously. This means AG headers get merged by the block layer and it can reduce the IO wait time by an order of magnitude or more. There are also mods to the secondary superblock update algorithm which make it more resilient in the face of writeback failures. We use a two pass update now - the main growfs loop now initialised secondary superblocks with sb_inprogess = 1 to indicate it is not in a valid state before we make any modifications, then after teh transactional grow we do a second pass to set sb_inprogess = 0 and mark them valid. This means that if we fail to write any secondary superblock, repair is not going to get confused by partial grow state. If we crash during the initial write, nothing has changed in the primary superblock. If we crash after the primary sb grow, then we'll know exactly what secondary superblocks did not get updated because they'll be the ones with sb_inprogress = 1 in them. Hence the recovery process becomes much easier as the parts of the fs that need updating are obvious.... Cheers, Dave. -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
