Copyright (c) 1996 Doug Rabson All rights reserved. This program is free software. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in...
NAMEVOP_READ VOP_WRITE - read or write a file
SYNOPSISIn sys/param.h In sys/vnode.h In sys/uio.h Ft int Fn VOP_READ struct vnode *vp struct uio *uio int ioflag struct ucred *cred Ft int Fn VOP_WRITE struct vnode *vp struct uio *uio int ioflag struct ucred *cred
DESCRIPTIONThese entry points read or write the contents of a file
The arguments are:
- Fa vp
- The vnode of the file.
- Fa uio
- The location of the data to be read or written.
- Fa ioflag
- Various flags.
- Fa cnp
- The credentials of the caller.
The Fa ioflag argument is used to give directives and hints to the file system. When attempting a read, the high 16 bits are used to provide a read-ahead hint (in units of file system blocks) that the file system should attempt. The low 16 bits are a bit mask which can contain the following flags:
- Do I/O as atomic unit.
- Append write to end.
- Do I/O synchronously.
- Underlying node already locked.
- FNDELAY flag set in file table.
- Data already in VMIO space.
LOCKSThe file should be locked on entry and will still be locked on exit.
RETURN VALUESZero is returned on success, otherwise an error code is returned.
- Bq Er EFBIG
- An attempt was made to write a file that exceeds the process's file size limit or the maximum file size.
- Bq Er ENOSPC
- The file system is full.
- Bq Er EPERM
- An append-only flag is set on the file, but the caller is attempting to write before the current end of file.