Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752947AbaBXPCU (ORCPT ); Mon, 24 Feb 2014 10:02:20 -0500 Received: from mail-wg0-f48.google.com ([74.125.82.48]:57370 "EHLO mail-wg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752723AbaBXPCS (ORCPT ); Mon, 24 Feb 2014 10:02:18 -0500 MIME-Version: 1.0 In-Reply-To: <530B4AFB.5060006@redhat.com> References: <1393221070-21674-1-git-send-email-iamjoonsoo.kim@lge.com> <530B4AFB.5060006@redhat.com> Date: Tue, 25 Feb 2014 00:02:15 +0900 Message-ID: Subject: Re: [PATCH] zram: support REQ_DISCARD From: Joonsoo Kim To: Jerome Marchand Cc: Joonsoo Kim , Andrew Morton , Minchan Kim , Nitin Gupta , LKML , Sergey Senozhatsky Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014-02-24 22:36 GMT+09:00 Jerome Marchand : > On 02/24/2014 06:51 AM, Joonsoo Kim wrote: >> zram is ram based block device and can be used by backend of filesystem. >> When filesystem deletes a file, it normally doesn't do anything on data >> block of that file. It just marks on metadata of that file. This behavior >> has no problem on disk based block device, but has problems on ram based >> block device, since we can't free memory used for data block. To overcome >> this disadvantage, there is REQ_DISCARD functionality. If block device >> support REQ_DISCARD and filesystem is mounted with discard option, >> filesystem sends REQ_DISCARD to block device whenever some data blocks are >> discarded. All we have to do is to handle this request. >> >> This patch implements to flag up QUEUE_FLAG_DISCARD and handle this >> REQ_DISCARD request. With it, we can free memory used by zram if it isn't >> used. >> >> Signed-off-by: Joonsoo Kim >> --- >> This patch is based on master branch of linux-next tree. >> >> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c >> index 5ec61be..cff2c0e 100644 >> --- a/drivers/block/zram/zram_drv.c >> +++ b/drivers/block/zram/zram_drv.c >> @@ -501,6 +501,20 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index, >> return ret; >> } >> >> +static void zram_bio_discard(struct zram *zram, struct bio *bio) >> +{ >> + u32 index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT; > > Hi Joonsoo, > > If bi_sector is not aligned on a page size, we might end up discarding > a page that still contain valid data. > > Hello, Jerome. Is it possible that request isn't aligned on a page size if logical/physical block size is PAGE_SIZE? When I tested it, I didn't find any invalid io. If we meet any misaligned request, it would be filtered by valid_io_request(). :) Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/