[ Bottom of Page | Previous Page | Next Page | Contents | Index | Library Home |
Legal |
Search ]
Technical Reference: Kernel and Subsystems, Volume 1
vfs_cntl Entry Point
Purpose
Implements control operations for a file system.
Syntax
int vfs_cntl (vfsp, cmd, arg, argsize, crp)
struct vfs * vfsp;
int cmd;
caddr_t arg;
unsigned long argsize;
struct ucred * crp;
Parameters
vfsp |
Points to the file system for which the control operation is to be
issued. |
cmd |
Specifies which control operation to perform. |
arg |
Identifies data specific to the control operation. |
argsize |
Identifies the length of the data specified by the arg parameter. |
crp |
Points to the cred structure. This structure
contains data that the file system can use to validate access permission. |
Description
The vfs_cntl entry point is
invoked by the logical file system to request various control operations on
the underlying file system. A file system implementation
can define file system-specific cmd parameter values
and corresponding control functions. The cmd parameter
for these functions should have a minimum value of 32768. These control operations
can be issued with the fscntl
subroutine.
Note
The only system-supported control operation is FS_EXTENDFS. This operation increases the file system size and accepts
an arg parameter that specifies the new size. The FS_EXTENDFS operation ignores the argsize parameter.
Execution Environment
The vfs_cntl entry point can
be called from the process environment only.
Return Values
Non-zero return values are returned from the /usr/include/sys/errno.h file to indicate failure. Typical values include:
EINVAL |
Indicates that the cmd parameter is not a
supported control, or the arg parameter is not a valid
argument for the command. |
EACCES |
Indicates that the cmd parameter requires
a privilege that the current process does not have. |
Related Information
The fscntl subroutine.
Virtual File System Overview, Virtual File System Kernel Extensions Overview, Logical File System Overview, Understanding Virtual Nodes (V-nodes) in AIX 5L Version 5.2 Kernel Extensions and Device Support Programming Concepts.
[ Top of Page | Previous Page | Next Page | Contents | Index | Library Home |
Legal |
Search ]