freebsd-dev/share/man/man9/VOP_FSYNC.9

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.\" Copyright (c) 1996 Doug Rabson
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.Dd July 24, 1996
.Os
.Dt VOP_FSYNC 9
.Sh NAME
.Nm VOP_FSYNC
.Nd flush filesystem buffers for a file
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fn VOP_FSYNC "struct vnode *vp" "struct ucred *cred" "int waitfor" "struct thread *td"
.Sh DESCRIPTION
This call flushes any dirty filesystem buffers for the file.
It is used to implement the
.Xr sync 2
and
.Xr fsync 2
system calls.
.Pp
Its arguments are:
.Bl -tag -width waitfor
.It Ar vp
the vnode of the file
.It Ar cred
the caller's credentials
.It Ar waitfor
whether the function should wait for I/O to complete.
Possible values are:
.Bl -tag -width MNT_NOWAIT
.It Dv MNT_WAIT
synchronously wait for I/O to complete
.It Dv MNT_NOWAIT
start all I/O, but do not wait for it
.It Dv MNT_LAZY
push data not written by filesystem syncer
.El
.It Ar td
the calling thread
.El
.Pp
The argument
.Fa waitfor
is either
.Dv MNT_WAIT
or
.Dv MNT_NOWAIT
and specifies whether or not the function should wait for the writes
to finish before returning.
.Sh LOCKS
The file should be locked on entry.
.Sh RETURN VALUES
Zero is returned if the call is successful, otherwise an appropriate
error code is returned.
.Sh PSEUDOCODE
.Bd -literal
int
vop_fsync(struct vnode *vp, struct ucred *cred, int waitfor, struct thread *td)
{
    struct buf *bp;
    struct buf *nbp;
    struct timeval tv;
    int s;

loop:
    s = splbio();
    for (bp = vp->v_dirtyblkhd.lh_first; bp; bp = nbp) {
	nbp = bp->b_vnbufs.le_next;

	/*
	 * Ignore buffers which are already being written.
	 */
	if (bp->b_flags & B_BUSY)
	    continue;

	/*
	 * Make sure the buffer is dirty.
	 */
	if ((bp->b_flags & B_DELWRI) == 0)
	    panic("vop_fsync: not dirty");

	vfs_bio_awrite(bp);
	splx(s);
	goto loop;
    }
    splx(s);

    if (waitfor == MNT_WAIT) {
	s = splbio();
	while (vp->v_numoutput) {
	    vp->v_flag |= VBWAIT;
	    tsleep((caddr_t)&vp->v_numoutput, PRIBIO + 1, "vopfsn");
	}
	splx(s);
#ifdef DIAGNOSTIC
	if (vp->v_dirtyblkhd.lh_first) {
	    vprint("vop_fsync: dirty", vp);
	    goto loop;
	}
#endif
    }

    /*
     * Write out the on-disc version of the vnode.
     */
    tv = time;
    return VOP_UPDATE(vp, &tv, &tv, waitfor == MNT_WAIT);
}
.Ed
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ENOSPC
The filesystem is full.
.It Bq Er EDQUOT
Quota exceeded.
.El
.Sh SEE ALSO
.Xr vnode 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .