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.TH "NFS_FILE_DIRECT_READ" "9" "09 October 2005" "" ""

.SH NAME
nfs_file_direct_read \- file direct read operation for NFS files
.SH SYNOPSIS
"SYNOPSIS"
.sp
\fB
.sp
ssize_t nfs_file_direct_read  (struct kiocb * \fIiocb\fB, char __user * \fIbuf\fB, size_t \fIcount\fB, loff_t \fIpos\fB);
\fR
.SH "ARGUMENTS"
.TP
\fB\fIiocb\fB\fR
target I/O control block
.TP
\fB\fIbuf\fB\fR
user's buffer into which to read data
.TP
\fB\fIcount\fB\fR
-- undescribed --
.TP
\fB\fIpos\fB\fR
-- undescribed --
.SH "COUNT"
.PP
number of bytes to read
.SH "POS"
.PP
byte offset in file where reading starts
.PP
We use this function for direct reads instead of calling
\fBgeneric_file_aio_read\fR in order to avoid gfar's check to see if
the request starts before the end of the file.  For that check
to work, we must generate a GETATTR before each direct read, and
even then there is a window between the GETATTR and the subsequent
READ where the file size could change.  So our preference is simply
to do all reads the application wants, and the server will take
care of managing the end of file boundary.
.PP
This function also eliminates unnecessarily updating the file's
atime locally, as the NFS server sets the file's atime, and this
client must read the updated atime from the server back into its
cache.