Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752763AbaBZNUG (ORCPT ); Wed, 26 Feb 2014 08:20:06 -0500 Received: from mail-ea0-f171.google.com ([209.85.215.171]:43686 "EHLO mail-ea0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752086AbaBZNUE (ORCPT ); Wed, 26 Feb 2014 08:20:04 -0500 Date: Wed, 26 Feb 2014 16:16:26 +0300 From: Sergey Senozhatsky To: Joonsoo Kim Cc: Andrew Morton , Minchan Kim , Nitin Gupta , linux-kernel@vger.kernel.org, Jerome Marchand , Joonsoo Kim Subject: Re: [PATCH v2] zram: support REQ_DISCARD Message-ID: <20140226131625.GA2217@swordfish.minsk.epam.com> References: <1393392195-20743-1-git-send-email-iamjoonsoo.kim@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1393392195-20743-1-git-send-email-iamjoonsoo.kim@lge.com> User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On (02/26/14 14:23), 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; > + 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; > + } > +} > + a side note, do we need zram_bio_discard() function? I mean, can we handle discard request in zram_bvec_rw(), where we already know index, etc. (passed from __zram_make_request())? for example: @@ -510,6 +510,11 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index, ret = zram_bvec_write(zram, bvec, index, offset); } + if (unlikely(bio->bi_rw & REQ_DISCARD)) { + write_lock(&zram->meta->tb_lock); + zram_free_page(zram, index); + write_unlock(&zram->meta->tb_lock); + } return ret; } -ss > 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; > + queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue); > > add_disk(zram->disk); > > -- > 1.7.9.5 > -- 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/