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<table class="head">
<tr>
<td class="head-ltitle">VOP_LOCK(9)</td>
<td class="head-vol">Kernel Developer's Manual</td>
<td class="head-rtitle">VOP_LOCK(9)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">VOP_LOCK</code>,
<code class="Nm">VOP_UNLOCK</code>, <code class="Nm">VOP_ISLOCKED</code>,
<code class="Nm">vn_lock</code> — <span class="Nd">serialize access
to a vnode</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="In">#include
<<a class="In">sys/param.h</a>></code>
<br/>
<code class="In">#include <<a class="In">sys/lock.h</a>></code>
<br/>
<code class="In">#include <<a class="In">sys/vnode.h</a>></code></p>
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">VOP_LOCK</code>(<var class="Fa" style="white-space: nowrap;">struct
vnode *vp</var>, <var class="Fa" style="white-space: nowrap;">int
flags</var>);</p>
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">VOP_UNLOCK</code>(<var class="Fa" style="white-space: nowrap;">struct
vnode *vp</var>);</p>
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">VOP_ISLOCKED</code>(<var class="Fa" style="white-space: nowrap;">struct
vnode *vp</var>);</p>
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">vn_lock</code>(<var class="Fa" style="white-space: nowrap;">struct
vnode *vp</var>, <var class="Fa" style="white-space: nowrap;">int
flags</var>);</p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">These calls are used to serialize access to the file system, such
as to prevent two writes to the same file from happening at the same
time.</p>
<p class="Pp">The arguments are:</p>
<dl class="Bl-tag">
<dt><var class="Fa">vp</var></dt>
<dd>The vnode being locked or unlocked.</dd>
<dt><var class="Fa">flags</var></dt>
<dd>One of the lock request types:
<p class="Pp"></p>
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt id="LK_SHARED"><a class="permalink" href="#LK_SHARED"><code class="Dv">LK_SHARED</code></a></dt>
<dd>Shared lock.</dd>
<dt id="LK_EXCLUSIVE"><a class="permalink" href="#LK_EXCLUSIVE"><code class="Dv">LK_EXCLUSIVE</code></a></dt>
<dd>Exclusive lock.</dd>
<dt id="LK_UPGRADE"><a class="permalink" href="#LK_UPGRADE"><code class="Dv">LK_UPGRADE</code></a></dt>
<dd>Shared-to-exclusive upgrade.</dd>
<dt id="LK_DOWNGRADE"><a class="permalink" href="#LK_DOWNGRADE"><code class="Dv">LK_DOWNGRADE</code></a></dt>
<dd>Exclusive-to-shared downgrade.</dd>
<dt id="LK_RELEASE"><a class="permalink" href="#LK_RELEASE"><code class="Dv">LK_RELEASE</code></a></dt>
<dd>Release any type of lock.</dd>
<dt id="LK_DRAIN"><a class="permalink" href="#LK_DRAIN"><code class="Dv">LK_DRAIN</code></a></dt>
<dd>Wait for all lock activity to end.</dd>
</dl>
</div>
<p class="Pp">The lock type may be <i class="Em">or</i>'ed with these lock
flags:</p>
<p class="Pp"></p>
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt id="LK_NOWAIT"><a class="permalink" href="#LK_NOWAIT"><code class="Dv">LK_NOWAIT</code></a></dt>
<dd>Do not sleep to wait for lock.</dd>
<dt id="LK_SLEEPFAIL"><a class="permalink" href="#LK_SLEEPFAIL"><code class="Dv">LK_SLEEPFAIL</code></a></dt>
<dd>Sleep, then return failure.</dd>
<dt id="LK_CANRECURSE"><a class="permalink" href="#LK_CANRECURSE"><code class="Dv">LK_CANRECURSE</code></a></dt>
<dd>Allow recursive exclusive lock.</dd>
<dt id="LK_NOWITNESS"><a class="permalink" href="#LK_NOWITNESS"><code class="Dv">LK_NOWITNESS</code></a></dt>
<dd>Instruct <a class="Xr">witness(4)</a> to ignore this instance.</dd>
</dl>
</div>
<p class="Pp">The lock type may be <i class="Em">or</i>'ed with these
control flags:</p>
<p class="Pp"></p>
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt id="LK_INTERLOCK"><a class="permalink" href="#LK_INTERLOCK"><code class="Dv">LK_INTERLOCK</code></a></dt>
<dd>Specify when the caller already has a simple lock
(<a class="permalink" href="#VOP_LOCK"><code class="Fn" id="VOP_LOCK">VOP_LOCK</code></a>()
will unlock the simple lock after getting the lock).</dd>
<dt id="LK_RETRY"><a class="permalink" href="#LK_RETRY"><code class="Dv">LK_RETRY</code></a></dt>
<dd>Retry until locked.</dd>
</dl>
</div>
<p class="Pp" id="vn_lock">Kernel code should use
<a class="permalink" href="#vn_lock"><code class="Fn">vn_lock</code></a>()
to lock a vnode rather than calling <code class="Fn">VOP_LOCK</code>()
directly. <code class="Fn">vn_lock</code>() also does not want a thread
specified as argument but it assumes curthread to be used.</p>
</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="RETURN_VALUES"><a class="permalink" href="#RETURN_VALUES">RETURN
VALUES</a></h1>
<p class="Pp">Zero is returned on success, otherwise an error is returned.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">vnode(9)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">This manual page was written by <span class="An">Doug
Rabson</span>.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">August 23, 2022</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
