From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030356AbWARPwp (ORCPT ); Wed, 18 Jan 2006 10:52:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030358AbWARPwp (ORCPT ); Wed, 18 Jan 2006 10:52:45 -0500 Received: from ns2.suse.de ([195.135.220.15]:31892 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S1030356AbWARPwo (ORCPT ); Wed, 18 Jan 2006 10:52:44 -0500 Date: Wed, 18 Jan 2006 16:52:42 +0100 From: Nick Piggin To: Linus Torvalds Cc: Andrew Morton , Linux Kernel Mailing List Subject: [patch] sg: simplify page_count manipulations Message-ID: <20060118155242.GB28418@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Linus, What do you think about the following couple of patches? Hugh's had a look and thinks they're OK. Nick -- Allocate a compound page for the user mapping instead of tweaking the page refcounts. Signed-off-by: Nick Piggin Index: linux-2.6/drivers/scsi/sg.c =================================================================== --- linux-2.6.orig/drivers/scsi/sg.c +++ linux-2.6/drivers/scsi/sg.c @@ -1140,32 +1140,6 @@ sg_fasync(int fd, struct file *filp, int return (retval < 0) ? retval : 0; } -/* When startFinish==1 increments page counts for pages other than the - first of scatter gather elements obtained from alloc_pages(). - When startFinish==0 decrements ... */ -static void -sg_rb_correct4mmap(Sg_scatter_hold * rsv_schp, int startFinish) -{ - struct scatterlist *sg = rsv_schp->buffer; - struct page *page; - int k, m; - - SCSI_LOG_TIMEOUT(3, printk("sg_rb_correct4mmap: startFinish=%d, scatg=%d\n", - startFinish, rsv_schp->k_use_sg)); - /* N.B. correction _not_ applied to base page of each allocation */ - for (k = 0; k < rsv_schp->k_use_sg; ++k, ++sg) { - for (m = PAGE_SIZE; m < sg->length; m += PAGE_SIZE) { - page = sg->page; - if (startFinish) - get_page(page); - else { - if (page_count(page) > 0) - __put_page(page); - } - } - } -} - static struct page * sg_vma_nopage(struct vm_area_struct *vma, unsigned long addr, int *type) { @@ -1237,10 +1211,7 @@ sg_mmap(struct file *filp, struct vm_are sa += len; } - if (0 == sfp->mmap_called) { - sg_rb_correct4mmap(rsv_schp, 1); /* do only once per fd lifetime */ - sfp->mmap_called = 1; - } + sfp->mmap_called = 1; vma->vm_flags |= VM_RESERVED; vma->vm_private_data = sfp; vma->vm_ops = &sg_mmap_vm_ops; @@ -2395,8 +2366,6 @@ __sg_remove_sfp(Sg_device * sdp, Sg_fd * SCSI_LOG_TIMEOUT(6, printk("__sg_remove_sfp: bufflen=%d, k_use_sg=%d\n", (int) sfp->reserve.bufflen, (int) sfp->reserve.k_use_sg)); - if (sfp->mmap_called) - sg_rb_correct4mmap(&sfp->reserve, 0); /* undo correction */ sg_remove_scat(&sfp->reserve); } sfp->parentdp = NULL; @@ -2478,9 +2447,9 @@ sg_page_malloc(int rqSz, int lowDma, int return resp; if (lowDma) - page_mask = GFP_ATOMIC | GFP_DMA | __GFP_NOWARN; + page_mask = GFP_ATOMIC | GFP_DMA | __GFP_COMP | __GFP_NOWARN; else - page_mask = GFP_ATOMIC | __GFP_NOWARN; + page_mask = GFP_ATOMIC | __GFP_COMP | __GFP_NOWARN; for (order = 0, a_size = PAGE_SIZE; a_size < rqSz; order++, a_size <<= 1) ;