From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [patch][9/9] block: remove bio walking Date: Thu, 9 Sep 2004 17:49:14 +0200 Sender: linux-ide-owner@vger.kernel.org Message-ID: <20040909154914.GH1737@suse.de> References: <200409082127.04331.bzolnier@elka.pw.edu.pl> <200409091553.13918.bzolnier@elka.pw.edu.pl> <20040909150444.C6434@flint.arm.linux.org.uk> <200409091628.25304.bzolnier@elka.pw.edu.pl> <20040909155420.D6434@flint.arm.linux.org.uk> <20040909154453.GG1737@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:64642 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S266133AbUIIPuX (ORCPT ); Thu, 9 Sep 2004 11:50:23 -0400 Content-Disposition: inline In-Reply-To: <20040909154453.GG1737@suse.de> List-Id: linux-ide@vger.kernel.org To: Bartlomiej Zolnierkiewicz , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, Jeff Garzik On Thu, Sep 09 2004, Jens Axboe wrote: > On Thu, Sep 09 2004, Russell King wrote: > > Essentially, kernel PIO writes data into the page cache, and that action > > may leave data in the CPU's caches. Since the kernels mappings may not > > be coherent with mappings in userspace, data written to the kernel > > mappings may remain in the data cache, and stale data would be visible > > to user space. > > > > There has been talk about using flush_dcache_page() to resolve > > this issue, but I'm not sure what the outcome was. Certainly > > flush_dcache_page() is supposed to be used before the data in the > > kernels page cache is read or written. > > Have you ever tested bouncing on arm? It seems to be lacking a > flush_dcache_page() indeed, how does this look? > > ===== mm/highmem.c 1.51 vs edited ===== > --- 1.51/mm/highmem.c 2004-07-29 06:58:32 +02:00 > +++ edited/mm/highmem.c 2004-09-09 17:44:14 +02:00 > @@ -301,6 +301,7 @@ > vfrom = page_address(fromvec->bv_page) + tovec->bv_offset; > > bounce_copy_vec(tovec, vfrom); > + flush_dcache_page(tovec->bv_page); > } > } Not even enough, here's a better one. ===== mm/highmem.c 1.51 vs edited ===== --- 1.51/mm/highmem.c 2004-07-29 06:58:32 +02:00 +++ edited/mm/highmem.c 2004-09-09 17:47:58 +02:00 @@ -300,6 +300,7 @@ */ vfrom = page_address(fromvec->bv_page) + tovec->bv_offset; + flush_dcache_page(tovec->bv_page); bounce_copy_vec(tovec, vfrom); } } @@ -406,6 +407,7 @@ if (rw == WRITE) { char *vto, *vfrom; + flush_dcache_page(from->bv_page); vto = page_address(to->bv_page) + to->bv_offset; vfrom = kmap(from->bv_page) + from->bv_offset; memcpy(vto, vfrom, to->bv_len); -- Jens Axboe