Add a custom VOP_PATHCONF method for fdescfs.

The method handles NAME_MAX and LINK_MAX explicitly.  For all other
pathconf variables, the method passes the request down to the underlying
file descriptor.  This requires splitting a kern_fpathconf() syscallsubr
routine out of sys_fpathconf().  Also, to avoid lock order reversals with
vnode locks, the fdescfs vnode is unlocked around the call to
kern_fpathconf(), but with the usecount of the vnode bumped.

MFC after:	1 month
Sponsored by:	Chelsio Communications

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/sys/syscallsubr.h b/sys/sys/syscallsubr.h
index c97b27f1193a..d95b2dd7d4bf 100644
--- a/sys/sys/syscallsubr.h
+++ b/sys/sys/syscallsubr.h
@@ -111,6 +111,7 @@ int	kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg);
 int	kern_fcntl_freebsd(struct thread *td, int fd, int cmd, long arg);
 int	kern_fhstat(struct thread *td, fhandle_t fh, struct stat *buf);
 int	kern_fhstatfs(struct thread *td, fhandle_t fh, struct statfs *buf);
+int	kern_fpathconf(struct thread *td, int fd, int name);
 int	kern_fstat(struct thread *td, int fd, struct stat *sbp);
 int	kern_fstatfs(struct thread *td, int fd, struct statfs *buf);
 int	kern_fsync(struct thread *td, int fd, bool fullsync);