Date: Thu, 8 Jul 2010 14:47:05 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Andre Oppermann <andre@freebsd.org> Cc: lstewart@freebsd.org, bz@freebsd.org, Ming Fu <Ming.Fu@watchguard.com>, Andriy Gapon <avg@icyb.net.ua>, freebsd-net@freebsd.org Subject: Re: kern/123095 kern/131602 sendfile Message-ID: <20100708114705.GC2408@deviant.kiev.zoral.com.ua> In-Reply-To: <4C35B7C4.40507@freebsd.org> References: <7C3D15DD6E8F464998CA1470D8A322F302BB9F72@ES02CO.wgti.net> <20100707205041.GO13238@deviant.kiev.zoral.com.ua> <4C358843.5000001@freebsd.org> <4C358A01.8080206@icyb.net.ua> <20100708082943.GB2439@deviant.kiev.zoral.com.ua> <4C358EE5.8070003@icyb.net.ua> <20100708094255.GA2408@deviant.kiev.zoral.com.ua> <4C35B7C4.40507@freebsd.org>
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On Thu, Jul 08, 2010 at 01:34:28PM +0200, Andre Oppermann wrote:
> On 08.07.2010 11:42, Kostik Belousov wrote:
> >On Thu, Jul 08, 2010 at 11:40:05AM +0300, Andriy Gapon wrote:
> >>on 08/07/2010 11:29 Kostik Belousov said the following:
> >>>Right, the patch maps the page in sf buffer read-only (on i386 only).
> >>>But note the parallel posting with m_cat() change. It is still not
> >>>enough,
> >>>and I am not set up for the real network testing ATM.
> >>
> >>Could you also try to experiment with mb_dupcl?
> >>Namely transfer M_RDONLY from source mbuf.
> >
> >Right, it is it.
> >
> >Below is my current patch including debugging facilities that seems to
> >work.
> >Real changes that needed are in m_cat and mb_dupcl.
> >
> ...
> >diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
> >index f41eb03..1701ef2 100644
> >--- a/sys/kern/uipc_mbuf.c
> >+++ b/sys/kern/uipc_mbuf.c
> >@@ -301,7 +301,7 @@ mb_dupcl(struct mbuf *n, struct mbuf *m)
> > n->m_ext.ext_size = m->m_ext.ext_size;
> > n->m_ext.ref_cnt = m->m_ext.ref_cnt;
> > n->m_ext.ext_type = m->m_ext.ext_type;
> >- n->m_flags |= M_EXT;
> >+ n->m_flags |= M_EXT | (M_RDONLY & m->m_flags);
> > }
>
> Having the M_EXT flag always implies readonly and M_WRITABLE gets this
> right. Not inheriting all the flags from the source seems questionable.
> So IMHO this should be done here:
>
> n->m_flags |= (M_EXT | m->m_flags)
>
> > /*
> >@@ -911,7 +911,8 @@ m_cat(struct mbuf *m, struct mbuf *n)
> > m = m->m_next;
> > while (n) {
> > if (m->m_flags& M_EXT ||
> >- m->m_data + m->m_len + n->m_len>=&m->m_dat[MLEN]) {
> >+ m->m_data + m->m_len + n->m_len>=&m->m_dat[MLEN] ||
> >+ !M_WRITABLE(m)) {
>
> Here you can fully replace the (m->m_flags & M_EXT) test with
> M_WRITABLE(). The M_EXT test is included in it.
>
> > /* just join the two chains */
> > m->m_next = n;
> > return;
The patch is below. Works as well for me, thank you for the feedback.
diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index f41eb03..58567a4 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -301,7 +301,7 @@ mb_dupcl(struct mbuf *n, struct mbuf *m)
n->m_ext.ext_size = m->m_ext.ext_size;
n->m_ext.ref_cnt = m->m_ext.ref_cnt;
n->m_ext.ext_type = m->m_ext.ext_type;
- n->m_flags |= M_EXT;
+ n->m_flags |= M_EXT | m->m_flags;
}
/*
@@ -910,7 +910,7 @@ m_cat(struct mbuf *m, struct mbuf *n)
while (m->m_next)
m = m->m_next;
while (n) {
- if (m->m_flags & M_EXT ||
+ if (!M_WRITABLE(m) ||
m->m_data + m->m_len + n->m_len >= &m->m_dat[MLEN]) {
/* just join the two chains */
m->m_next = n;
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