On Sat, Jun 04, 2011 at 01:25:52AM +0100, Al Viro wrote: > On Thu, Jun 02, 2011 at 05:01:01PM +1000, Dave Chinner wrote: > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > The inode unused list is currently a global LRU. This does not match > > the other global filesystem cache - the dentry cache - which uses > > per-superblock LRU lists. Hence we have related filesystem object > > types using different LRU reclaimation schemes. > > > > To enable a per-superblock filesystem cache shrinker, both of these > > caches need to have per-sb unused object LRU lists. Hence this patch > > converts the global inode LRU to per-sb LRUs. > > > > The patch only does rudimentary per-sb propotioning in the shrinker > > infrastructure, as this gets removed when the per-sb shrinker > > callouts are introduced later on. > > What protects s_nr_inodes_unused? For this patch, the modifications are protected by the inode_lru_lock, but the reads are unprotected. That's the same protection as the inode_stat.nr_unused field, and the same as the existing dentry cache per-sb LRU accounting. In the next patch modifcations are moved under the sb->s_inode_lru_lock, but reads still remain unprotected. I can see how the multiple reads in shrink_icache_sb() could each return a different value during the proportioning, but I don't think that is a big problem. That proportioning code goes away in the next patch and is replaced by different code in prune_super(), so if you want the reads protected by locks or a single snapshot used for the proportioning calculations I'll do it in the new code in prune_super(). 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
