cephfs inode size handling and inode_drop field in struct MetaRequest

I'm working on a F_SETLEASE implementation for kcephfs, and am hitting a deadlock of sorts, due to a truncate triggering a cap revoke at an inopportune time. The issue is that truncates to a smaller size are always done via synchronous call to the MDS, whereas a truncate larger does not if Fx caps are held. That synchronous call causes the MDS to issue the client a cap revoke for caps that the lease holds references on (Frw, in particular). The client code has been this way since the inception and I haven't been able to locate any rationale for it. Some questions about this: 1) Why doesn't the client ever buffer a truncate to smaller size? It seems like that is something that could be done without a synchronous MDS call if we hold Fx caps. 2) The client setattr implementations set inode_drop values in the MetaRequest, but as far as I can tell, those values end up being ignored by the MDS. What purpose does inode_drop actually serve? Is this field vestigial? Thanks, -- Jeff Layton <jlayton(a)redhat.com>