Date: Fri, 9 Jan 2015 12:08:52 +0000 (UTC) From: Robert Watson <rwatson@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r276884 - head/sys/kern Message-ID: <201501091208.t09C8qJD025072@svn.freebsd.org>
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Author: rwatson Date: Fri Jan 9 12:08:51 2015 New Revision: 276884 URL: https://svnweb.freebsd.org/changeset/base/276884 Log: Remove a 'This is dumb' comment that has been incorrect for at least a decade: m_pulldown() is willing to consider ordinary mbufs writable. Retain another, related, and also outdated comment, but with a caveat that it is partially stale. Do not, for now, address the problem that it raises (that only EXT_CLUSTER external storage is considered writable, regardless of the results of M_WRITABLE() on the mbuf). MFC after: 3 days Sponsored by: EMC / Isilon Storage Division Modified: head/sys/kern/uipc_mbuf2.c Modified: head/sys/kern/uipc_mbuf2.c ============================================================================== --- head/sys/kern/uipc_mbuf2.c Fri Jan 9 10:59:49 2015 (r276883) +++ head/sys/kern/uipc_mbuf2.c Fri Jan 9 12:08:51 2015 (r276884) @@ -131,6 +131,8 @@ m_pulldown(struct mbuf *m, int off, int } /* + * The following comment is dated but still partially applies: + * * XXX: This code is flawed because it considers a "writable" mbuf * data region to require all of the following: * (i) mbuf _has_ to have M_EXT set; if it is just a regular @@ -148,10 +150,6 @@ m_pulldown(struct mbuf *m, int off, int * M_WRITABLE(). For now, we only evaluate once at the beginning and * live with this. */ - /* - * XXX: This is dumb. If we're just a regular mbuf with no M_EXT, - * then we're not "writable," according to this code. - */ writable = 0; if ((n->m_flags & M_EXT) == 0 || (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
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