On Sat, May 15, 2010 at 02:30:05AM +0100, Al Viro wrote: > On Fri, May 14, 2010 at 05:24:18PM +1000, Dave Chinner wrote: > > > > This series reworks the filesystem shrinkers. We currently have a > > set of issues with the current filesystem shrinkers: > > > > 1. There is an dependency between dentry and inode cache > > shrinking that is only implicitly defined by the order of > > shrinker registration. > > 2. The shrinkers need to walk the superblock list and pin > > the superblock to avoid unmount races with the sb going > > away. > > 3. The dentry cache uses per-superblock LRUs and proportions > > reclaim between all the superblocks which means we are > > doing breadth based reclaim. This means we touch every > > superblock for every shrinker call, and may only reclaim > > a single dentry at a time from a given superblock. > > 4. The inode cache has a global LRU, so it has different > > reclaim patterns to the dentry cache, despite the fact > > that the dentry cache is generally the only thing that > > pins inodes in memory. > > 5. Filesystems need to register their own shrinkers for > > caches and can't co-ordinate them with the dentry and > > inode cache shrinkers. > > NAK in that form; sb refcounting and iterators had been reworked for .34, > so at least it needs rediff on top of that. The tree I based this on was 2.6.34-rc7 - is there new code in a -next branch somewhere? > What's more, it's very > obviously broken wrt locking - you are unregistering a shrinker > from __put_super(). I.e. grab rwsem exclusively under a spinlock. > Essentially, you've turned dropping a _passive_ reference to superblock > (currently an operation safe in any context) into an operation allowed > only when no fs or vm locks are held by caller. Not going to work... Yeah, I picked that up after I posted it. My bad - I'll look into how I can rework that for the next iteration. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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
