On Thu, Jun 15, 2017 at 11:17:10AM -0700, Shaohua Li wrote: > From: Shaohua Li <shli@xxxxxx> > > Set i_generation for kernfs inode. This is required to implement > exportfs operations. The generation is 32-bit, so it's possible the > generation wraps up and we find stale files. To reduce the posssibility, > we don't reuse inode numer immediately. When the inode number allocation > wraps, we increase generation number. In this way generation/inode > number consist of a 64-bit number which is unlikely duplicated. This > does make the idr tree more sparse and waste some memory. Since idr > manages 32-bit keys, idr uses a 6-level radix tree, each level covers 6 > bits of the key. In a 100k inode kernfs, the worst case will have around > 300k radix tree node. Each node is 576bytes, so the tree will use about > ~150M memory. Sounds not too bad, if this really is a problem, we should > find better data structure. > > Signed-off-by: Shaohua Li <shli@xxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun
