On Mon, 6 Apr 2009, Kadlecsik Jozsef wrote: > On Sun, 5 Apr 2009, Wendy Cheng wrote: > > > Based on code reading ... > > 1. iput() gets inode_lock (a spin lock) > > 2. iput() calls iput_final() > > 3. iput_final() calls gfs_drop_inode() that calls > > generic_drop_inode() > > 4. generic_drop_inode() unlocks inode_lock. > > > > In theory, this logic violates the usage of spin lock as it is expected > > to lock for a short period of time but gfs_drop_inode() could take a > > while to finish. It has a blocking write page that need to make sure the > > data gets sync-ed to storage before it can returns. Make matter worse is > > that inode_lock is a global lock that could block non-GFS threads. One > > would think a quick fix is to drop the inode_lock at the beginning of > > gfs_drop_inode() and then re-acquires it after gfs sync the page. > > Unfortunately, inode_lock is not an exported symbol and GFS is an > > out-of-tree filesystem that has to be compiled as a kernel module. So > > this trick won't work for GFS. > > Actually, it can work. inode_lock is not private and gfs can unlock/lock > it: Darn, it's not EXPORTED! Anyway, I'll patch the kernel and will test it. Best regards, Jzosef -- E-mail : kadlec@xxxxxxxxxxxx, kadlec@xxxxxxxxxxxxxxxxx PGP key: http://www.kfki.hu/~kadlec/pgp_public_key.txt Address: KFKI Research Institute for Particle and Nuclear Physics H-1525 Budapest 114, POB. 49, Hungary -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
