From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752256AbaCFIYK (ORCPT ); Thu, 6 Mar 2014 03:24:10 -0500 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:32826 "EHLO lgemrelse6q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919AbaCFIYI (ORCPT ); Thu, 6 Mar 2014 03:24:08 -0500 X-Original-SENDERIP: 10.177.222.157 X-Original-MAILFROM: minchan@kernel.org Date: Thu, 6 Mar 2014 17:24:10 +0900 From: Minchan Kim To: Joonsoo Kim Cc: Joonsoo Kim , Andrew Morton , Nitin Gupta , LKML , Sergey Senozhatsky , Jerome Marchand Subject: Re: [PATCH v2] zram: support REQ_DISCARD Message-ID: <20140306082410.GB14287@bbox> References: <1393392195-20743-1-git-send-email-iamjoonsoo.kim@lge.com> <20140226080732.GF4606@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 01, 2014 at 12:24:37AM +0900, Joonsoo Kim wrote: > 2014-02-26 17:07 GMT+09:00 Minchan Kim : > > Hi Joonsoo, > > > > On Wed, Feb 26, 2014 at 02:23:15PM +0900, 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. > >> > >> v2: handle unaligned case commented by Jerome > >> > >> Signed-off-by: Joonsoo Kim > >> > >> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > >> index 5ec61be..5364c1e 100644 > >> --- a/drivers/block/zram/zram_drv.c > >> +++ b/drivers/block/zram/zram_drv.c > >> @@ -501,6 +501,36 @@ 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; > >> + size_t n = bio->bi_iter.bi_size; > > > > Nitpick: > > Please use more meaningful name(ex, len) rather than 'n'. > > > > Hello, Minchan. > > Will do. > > >> + size_t misalign; > >> + > >> + * On some arch, logical block (4096) aligned request couldn't be > >> + * aligned to PAGE_SIZE, since their PAGE_SIZE aren't 4096. > >> + * Therefore we should handle this misaligned case here. > >> + */ > >> + misalign = (bio->bi_iter.bi_sector & > >> + (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT; > >> + if (misalign) { > >> + if (n < misalign) > >> + return; > >> + > >> + n -= misalign; > >> + index++; > >> + } > >> + > >> + while (n >= PAGE_SIZE) { > >> + write_lock(&zram->meta->tb_lock); > >> + zram_free_page(zram, index); > >> + write_unlock(&zram->meta->tb_lock); > >> + index++; > >> + n -= PAGE_SIZE; > >> + } > >> +} > >> + > >> static void zram_reset_device(struct zram *zram, bool reset_capacity) > >> { > >> size_t index; > >> @@ -618,6 +648,12 @@ static void __zram_make_request(struct zram *zram, struct bio *bio) > >> struct bio_vec bvec; > >> struct bvec_iter iter; > >> > >> + if (unlikely(bio->bi_rw & REQ_DISCARD)) { > >> + zram_bio_discard(zram, bio); > >> + bio_endio(bio, 0); > >> + return; > >> + } > >> + > >> index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT; > >> offset = (bio->bi_iter.bi_sector & > >> (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT; > >> @@ -784,6 +820,10 @@ static int create_device(struct zram *zram, int device_id) > >> ZRAM_LOGICAL_BLOCK_SIZE); > >> blk_queue_io_min(zram->disk->queue, PAGE_SIZE); > >> blk_queue_io_opt(zram->disk->queue, PAGE_SIZE); > >> + zram->disk->queue->limits.discard_granularity = PAGE_SIZE; > >> + zram->disk->queue->limits.max_discard_sectors = UINT_MAX; > >> + zram->disk->queue->limits.discard_zeroes_data = 1; > > > > I don't know what discard_zeroes_data does mean. It seems we should > > make sure zram should return zero pages for discarded block on next > > time but prolblem could happen if you bail out in discard logic > > due to misalign but caller seem to know it was successful? > > > > What happens in this case? > > > > This will result in the problem what you think about. > I will change it like as following. > > if (PAGE_SIZE == ZRAM_LOGICAL_BLOCK_SIZE) > zram->disk->queue->limits.discard_zeroes_data = 1; > else > zram->disk->queue->limits.discard_zeroes_data = 0; > > Does It work for you? Yeb, pz, resend. > > 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/ -- Kind regards, Minchan Kim