kern/127213: [tmpfs] sendfile on tmpfs data corruption

[Maxim Konovalov]

The following reply was made to PR kern/127213; it has been noted by GNATS.

From: Maxim Konovalov <maxim at macomnet.ru>
To: Nate Eldredge <neldredge at math.ucsd.edu>
Cc: bug-followup at freebsd.org, JH <jh275 at s6.sector6.net>
Subject: Re: kern/127213: [tmpfs] sendfile on tmpfs data corruption
Date: Tue, 7 Oct 2008 07:43:17 +0400 (MSD)

 On Mon, 6 Oct 2008, 15:22-0700, Nate Eldredge wrote:
 
 > On Mon, 6 Oct 2008, Maxim Konovalov wrote:
 >
 > > Hello,
 > >
 > > On Mon, 6 Oct 2008, 06:40-0000, Nate Eldredge wrote:
 > >
 > > [...]
 > > >  Incidentally, to the initial reporter, what application do you have
 > > >  that requires sendfile?  In my experience, most things will fall
 > > >  back to a read/write loop if sendfile fails, since sendfile isn't
 > > >  available on all systems or under all circumstances.  So if you
 > > >  apply the quick fix so that sendfile always fails, it might at
 > > >  least get your application working again.
 > > >
 > > As stated in the PR Andrey used nginx (ports/www/nginx).  But I could
 > > easily reproduce the bug with the stock ftpd(8) with the ftproot on
 > > tmpfs.
 >
 > To simplify matters further, here is the testcase I used when
 > testing this, which uses sendfile to send some data over a unix
 > domain socket. Do:
 >
 > ./server /tmpfs/data mysocket &
 > ./client mysocket >data.out
 > cmp /tmpfs/data data.out
 >
 > If things work right, data and data.out should be identical.  But if
 > data is a file on a tmpfs, data.out contains apparently random
 > kernel memory contents.
 >
 Hi Nate,
 
 It'd be really nice if you extend
 src/tools/regression/sockets/sendfile regression test for this bug.
 Now it doesn't detect this case.
 
 -- 
 Maxim Konovalov