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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>journal_try_to_free_buffers</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="Linux Filesystems API" /><link rel="up" href="ch05s03.html#transaction_level" title="Transasction Level" /><link rel="prev" href="re208.html" title="journal_force_commit" /><link rel="next" href="re210.html" title="journal_invalidatepage" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>journal_try_to_free_buffers</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re208.html">Prev</a> </td><th width="60%" align="center">Transasction Level</th><td width="20%" align="right"> <a accesskey="n" href="re210.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="journal_try_to_free_buffers"><a id="API-journal-try-to-free-buffers"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>journal_try_to_free_buffers —
try to free page buffers.
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">journal_try_to_free_buffers </b>(</code></td><td>journal_t * <var class="pdparam">journal</var>, </td></tr><tr><td> </td><td>struct page * <var class="pdparam">page</var>, </td></tr><tr><td> </td><td>gfp_t <var class="pdparam">gfp_mask</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id3036248"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>journal</code></em></span></dt><dd><p>
journal for operation
</p></dd><dt><span class="term"><em class="parameter"><code>page</code></em></span></dt><dd><p>
to try and free
</p></dd><dt><span class="term"><em class="parameter"><code>gfp_mask</code></em></span></dt><dd><p>
we use the mask to detect how hard should we try to release
buffers. If __GFP_WAIT and __GFP_FS is set, we wait for commit code to
release the buffers.
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id3036311"></a><h2>Description</h2><p>
</p><p>
For all the buffers on this page,
if they are fully written out ordered data, move them onto BUF_CLEAN
so <code class="function">try_to_free_buffers</code> can reap them.
</p><p>
This function returns non-zero if we wish <code class="function">try_to_free_buffers</code>
to be called. We do this if the page is releasable by <code class="function">try_to_free_buffers</code>.
We also do it if the page has locked or dirty buffers and the caller wants
us to perform sync or async writeout.
</p><p>
This complicates JBD locking somewhat. We aren't protected by the
BKL here. We wish to remove the buffer from its committing or
running transaction's ->t_datalist via __journal_unfile_buffer.
</p><p>
This may *change* the value of transaction_t->t_datalist, so anyone
who looks at t_datalist needs to lock against this function.
</p><p>
Even worse, someone may be doing a journal_dirty_data on this
buffer. So we need to lock against that. <code class="function">journal_dirty_data</code>
will come out of the lock with the buffer dirty, which makes it
ineligible for release here.
</p><p>
Who else is affected by this? hmm... Really the only contender
is <code class="function">do_get_write_access</code> - it could be looking at the buffer while
<code class="function">journal_try_to_free_buffer</code> is changing its state. But that
cannot happen because we never reallocate freed data as metadata
while the data is part of a transaction. Yes?
</p><p>
Return 0 on failure, 1 on success
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re208.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch05s03.html#transaction_level">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re210.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>journal_force_commit</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>journal_invalidatepage</span></td></tr></table></div></body></html>
