From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755895Ab0EGJbY (ORCPT ); Fri, 7 May 2010 05:31:24 -0400 Received: from crca.org.au ([74.207.252.120]:51919 "EHLO crca.org.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755697Ab0EGJbT (ORCPT ); Fri, 7 May 2010 05:31:19 -0400 X-Greylist: delayed 521 seconds by postgrey-1.27 at vger.kernel.org; Fri, 07 May 2010 05:31:19 EDT X-Bogosity: Ham, spamicity=0.000000 Message-ID: <4BE3DBD6.7070707@tuxonice.net> Date: Fri, 07 May 2010 19:22:30 +1000 From: Nigel Cunningham Reply-To: nigel@tuxonice.net User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100423 Thunderbird/3.0.4 MIME-Version: 1.0 To: Nitin Gupta CC: Greg KH , Linus Torvalds , Pekka Enberg , Hugh Dickins , Cyp , Minchan Kim , Al Viro , Christoph Hellwig , Jens Axboe , Andi Kleen , Andrew Morton , driverdev , linux-kernel Subject: Re: [PATCH 2/3] Add swap slot free callback to block_device_operations References: <1273217107-2023-1-git-send-email-ngupta@vflare.org> <1273217107-2023-3-git-send-email-ngupta@vflare.org> In-Reply-To: <1273217107-2023-3-git-send-email-ngupta@vflare.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi. On 07/05/10 17:25, Nitin Gupta wrote: > This callback is required when RAM based devices are used as swap disks. > One such device is ramzswap which is used as compressed in-memory swap > disk. For such devices, we need a callback as soon as a swap slot is no > longer used to allow freeing memory allocated for this slot. Without this > callback, stale data can quickly accumulate in memory defeating the whole > purpose of such devices. > > Signed-off-by: Nitin Gupta > --- > include/linux/blkdev.h | 2 ++ > mm/swapfile.c | 4 ++++ > 2 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 6690e8b..413284a 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1287,6 +1287,8 @@ struct block_device_operations { > unsigned long long); > int (*revalidate_disk) (struct gendisk *); > int (*getgeo)(struct block_device *, struct hd_geometry *); > + /* this callback is with swap_lock and sometimes page table lock held */ > + void (*swap_slot_free_notify) (struct block_device *, unsigned long); > struct module *owner; > }; > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index ecb069e..f5ccc47 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -574,6 +574,7 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, > > /* free if no reference */ > if (!usage) { > + struct gendisk *disk = p->bdev->bd_disk; > if (offset< p->lowest_bit) > p->lowest_bit = offset; > if (offset> p->highest_bit) > @@ -583,6 +584,9 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, > swap_list.next = p->type; > nr_swap_pages++; > p->inuse_pages--; > + if ((p->flags& SWP_BLKDEV)&& > + disk->fops->swap_slot_free_notify) > + disk->fops->swap_slot_free_notify(p->bdev, offset); Is this p->flags & SWP_BLKDEV logic reversed? (Don't you want the notifier called for devices that aren't backed by a block device?) I also wonder whether leaving the p->flags & SWP_BLKDEV part out might be a good idea. Other potential notifier users? Regards, Nigel