From: "David S. Miller" <davem@redhat.com>
To: "David S. Miller" <davem@redhat.com>
Cc: willy@debian.org, James.Bottomley@SteelEye.com,
linux-kernel@vger.kernel.org,
parisc-linux@lists.parisc-linux.org, drepper@redhat.com
Subject: Re: [parisc-linux] Re: Problems with kernel mmap (failing tst-mmap-eofsync in glibc on parisc)
Date: Fri, 22 Aug 2003 11:01:44 -0700 [thread overview]
Message-ID: <20030822110144.5f7b83c5.davem@redhat.com> (raw)
In-Reply-To: <20030822103634.46a15747.davem@redhat.com>
On Fri, 22 Aug 2003 10:36:34 -0700
"David S. Miller" <davem@redhat.com> wrote:
> On Fri, 22 Aug 2003 18:41:03 +0100
> Matthew Wilcox <willy@debian.org> wrote:
>
> > Uhm. So what happens when the user has stored into the page and now
> > the kernel wants to read from it? There's still data in the cache for
> > the user mapping that's non-coherent with the kernel mapping.
>
> I see. This causes the page cache read flush_dcache_page() call
> not to trigger.
Wait, I'm confused again.
How can the user "write" to the mmap()'d side if PROT_WRITE
was not specified? That is the only case in which the proposed
patch could make a difference, we check this:
switch (flags & MAP_TYPE) {
case MAP_SHARED:
if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
return -EACCES;
Therefore if the user can write to the page, file->f_mode will
have the write bit set too.
So the proposed patch looks bogus to me.
next prev parent reply other threads:[~2003-08-22 18:01 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-22 14:40 Problems with kernel mmap (failing tst-mmap-eofsync in glibc on parisc) James Bottomley
2003-08-22 16:14 ` David S. Miller
2003-08-22 16:34 ` [parisc-linux] " Matthew Wilcox
2003-08-22 16:39 ` David S. Miller
2003-08-22 17:41 ` Matthew Wilcox
2003-08-22 17:36 ` David S. Miller
2003-08-22 18:01 ` David S. Miller [this message]
2003-08-22 18:34 ` Hugh Dickins
2003-08-22 18:31 ` David S. Miller
2003-08-22 18:56 ` James Bottomley
2003-08-22 19:19 ` David S. Miller
2003-08-22 22:27 ` James Bottomley
2003-08-22 22:41 ` David S. Miller
2003-08-23 1:09 ` James Bottomley
2003-08-23 7:22 ` Hugh Dickins
2003-08-23 15:59 ` James Bottomley
2003-08-23 21:44 ` David S. Miller
2003-08-23 21:43 ` David S. Miller
2003-08-23 22:21 ` James Bottomley
2003-08-23 22:51 ` David S. Miller
2003-08-23 23:01 ` James Bottomley
2003-08-23 22:53 ` David S. Miller
2003-08-23 23:11 ` James Bottomley
2003-08-24 0:22 ` David S. Miller
[not found] ` <1061702282.1992.1153.camel@mulgrave>
[not found] ` <20030823222300.4695a0c4.davem@redhat.com>
2003-08-24 16:54 ` James Bottomley
2003-08-22 18:41 ` James Bottomley
2003-08-22 19:02 ` Hugh Dickins
2003-08-22 19:09 ` Randolph Chung
2003-08-22 16:42 ` Russell King
2003-08-22 16:39 ` David S. Miller
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