---
name: "VOP_BMAP"
section: "9"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/VOP_BMAP"
---

# VOP\_BMAP(9)

Logical to physical block number conversion

## NAME

**VOP\_BMAP** – Logical to physical block number conversion

## SYNOPSIS

**#include \<sys/param.h\>**

**#include \<sys/vnode.h\>**

*int*\

**VOP\_BMAP**(*struct vnode \*vp*, *daddr\_t bn*, *struct bufobj \*\*bop*, *daddr\_t \*bnp*, *int \*runp*, *int \*runb*);

## DESCRIPTION

This vnode call is used to lookup the physical block number of the file system's underlying device where a given logical block of a file is stored. Its arguments are:

- *vp*

  The vnode of the file.

- *bn*

  Logical block number within the file identified by *vp*.

- *bop*

  Return storage for the buffer object associated with the file system's underlying device.

- *bnp*

  Return storage for the physical block number.

- *runp*

  Return storage for the number of succeeding logical blocks that may be efficiently read at the same time as the requested block. This will usually be the number of logical blocks whose physical blocks are contiguously allocated. However a file system is free to define "efficient" as it sees fit.

- *runb*

  Like *runp* but for preceding rather than succeeding blocks.

Any of the return arguments may be NULL to indicate that the caller does not care about that information.

## LOCKS

The vnode will be locked on entry and should remain locked on return.

## RETURN VALUES

Zero is returned on success, otherwise an error code is returned.

## SEE ALSO

[vnode(9)](/vnode/9.md)

## HISTORY

A **bmap**() function first appeared in 4.2BSD.

## AUTHORS

This manual page was written by Alan Somers.