Date: Thu, 12 Jan 2023 14:34:01 +0800
From: Zhang Mingli <zmlpostgres@gmail.com>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Message-ID: <1c7954e4-1705-4855-a99d-c77bf426c3e7@Spark>
In-Reply-To: <f937934f-5b6c-402c-a9ab-605bd07dcba9@Spark>
References: <f937934f-5b6c-402c-a9ab-605bd07dcba9@Spark>
Subject: Fix condition in shm_toc and remove unused function
 shm_toc_freespace.
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Hi, hackers

Some conditions in shm=5Ftoc=5Finsert and shm=5Ftoc=5Fallocate are bogus,=
 like:

	if (toc=5Fbytes + nbytes > total=5Fbytes =7C=7C toc=5Fbytes + nbytes < t=
oc=5Fbytes)

Remove the condition =60toc=5Fbytes + nbytes < toc=5Fbytes=60 and take a =
sizeof(shm=5Fentry) into account in shm=5Ftoc=5Fallocate though
shm=5Ftoc=5Fallocate does that too.

	/* Check for memory exhaustion and overflow. */
	- if (toc=5Fbytes + nbytes > total=5Fbytes =7C=7C toc=5Fbytes + nbytes <=
 toc=5Fbytes)
	+ if (toc=5Fbytes + sizeof(shm=5Ftoc=5Fentry) + nbytes > total=5Fbytes)
	 =7B
=C2=A0	SpinLockRelease(&toc->toc=5Fmutex);

shm=5Ftoc=5Ffreespace is introduced with shm=5Ftoc by original commit 6dd=
d5137b2, but is not used since then, so remove it.


Regards,
Zhang Mingli

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<html xmlns=3D=22http://www.w3.org/1999/xhtml=22>
<head>
<title></title>
</head>
<body>
<div name=3D=22messageBodySection=22>
<div dir=3D=22auto=22>Hi, hackers<br />
<br />
Some conditions in shm=5Ftoc=5Finsert and shm=5Ftoc=5Fallocate are bogus,=
 like:<br />
<span style=3D=22white-space:pre=22>	</span><br />
<span style=3D=22white-space:pre=22>	if (toc=5Fbytes + nbytes &gt; total=5F=
bytes =7C=7C toc=5Fbytes + nbytes &lt; toc=5Fbytes)</span><br />
<br />
Remove the condition =60toc=5Fbytes + nbytes &lt; toc=5Fbytes=60 and take=
 a sizeof(shm=5Fentry) into account in shm=5Ftoc=5Fallocate though&=23160=
;<br />
shm=5Ftoc=5Fallocate does that too.<br />
<br />
<span style=3D=22white-space:pre=22>	/* Check for memory exhaustion and o=
verflow. */</span><br />
<span style=3D=22white-space:pre=22>	- if (toc=5Fbytes + nbytes &gt; tota=
l=5Fbytes =7C=7C toc=5Fbytes + nbytes &lt; toc=5Fbytes)</span><br />
<span style=3D=22white-space:pre=22>	+ if (toc=5Fbytes + sizeof(shm=5Ftoc=
=5Fentry) + nbytes &gt; total=5Fbytes)</span><br />
<span style=3D=22white-space:pre=22>	 =7B</span><br />
<span style=3D=22white-space:pre=22>&=23160;	SpinLockRelease(&amp;toc-&gt=
;toc=5Fmutex);</span><br />
<br />
shm=5Ftoc=5Ffreespace is introduced with shm=5Ftoc by original commit 6dd=
d5137b2, but is not used since then, so remove it.<br />
<br /></div>
</div>
<div name=3D=22messageSignatureSection=22><br />
<div dir=3D=22auto=22><span style=3D=22color: var(--textColor); backgroun=
d-color: var(--backgroundColor);=22>Regards,</span><br /></div>
<div dir=3D=22auto=22>Zhang Mingli</div>
</div>
</body>
</html>

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