From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759030Ab0FVSAr (ORCPT ); Tue, 22 Jun 2010 14:00:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26332 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752002Ab0FVSAp (ORCPT ); Tue, 22 Jun 2010 14:00:45 -0400 Date: Tue, 22 Jun 2010 14:00:29 -0400 From: Mike Snitzer To: Christoph Hellwig Cc: axboe@kernel.dk, dm-devel@redhat.com, James.Bottomley@suse.de, linux-kernel@vger.kernel.org, martin.petersen@oracle.com Subject: Re: [PATCH, RFC] block: don't allocate a payload for discard request Message-ID: <20100622180029.GA15950@redhat.com> References: <20100618145942.GA1148@lst.de> <20100619042534.GA16217@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100619042534.GA16217@redhat.com> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jun 19 2010 at 12:25am -0400, Mike Snitzer wrote: > On Fri, Jun 18 2010 at 10:59am -0400, > Christoph Hellwig wrote: > > > > > Allocating a fixed payload for discard requests always was a horrible hack, > > and it's not coming to byte us when adding support for discard in DM/MD. > > > > So change the code to leave the allocation of a payload to the lowlevel > > driver. Unfortunately that means we'll need another hack, which allows > > us to update the various block layer length fields indicating that we > > have a payload. Instead of hiding this in sd.c, which we already partially > > do for UNMAP support add a documented helper in the core block layer for it. > > > > Signed-off-by: Christoph Hellwig > > Acked-by: Mike Snitzer > > I've built on your patch to successfully implement discard support for > DM (this includes splitting discards that span targets; only the linear > and striped DM targets are supported so far). I must retract my Acked-by because further testing has shown that this change results in OOM (on 2.6.34 with postmark benchmarking against ext4 w/ -o discard). The patch is _very_ desirable (simplifies DM's discard support, etc) but there is more work needed to get it stable. I'll continue tracking this OOM down. Mem-Info: Node 0 DMA per-cpu: CPU 0: hi: 0, btch: 1 usd: 0 CPU 1: hi: 0, btch: 1 usd: 0 Node 0 DMA32 per-cpu: CPU 0: hi: 186, btch: 31 usd: 91 CPU 1: hi: 186, btch: 31 usd: 92 active_anon:52 inactive_anon:65 isolated_anon:0 active_file:525 inactive_file:1275 isolated_file:0 unevictable:0 dirty:802 writeback:0 unstable:0 free:3411 slab_reclaimable:5386 slab_unreclaimable:7672 mapped:86 shmem:0 pagetables:576 bounce:0 Node 0 DMA free:8040kB min:40kB low:48kB high:60kB active_anon:0kB inactive_anon:0kB active_file:12kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15768kB mlocked:0kB dirty:0kB writeback:0kB mapped:8kB shmem:0kB slab_reclaimable:28kB slab_unreclaimable:16kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:22 all_unreclaimable? yes lowmem_reserve[]: 0 2003 2003 2003 Node 0 DMA32 free:5604kB min:5704kB low:7128kB high:8556kB active_anon:208kB inactive_anon:260kB active_file:2088kB inactive_file:4976kB unevictable:0kB isolated(anon):0kB isolated(file):128kB present:2052068kB mlocked:0kB dirty:3208kB writeback:0kB mapped:336kB shmem:0kB slab_reclaimable:21516kB slab_unreclaimable:30672kB kernel_stack:816kB pagetables:2304kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:608 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 Node 0 DMA: 4*4kB 3*8kB 1*16kB 2*32kB 2*64kB 3*128kB 3*256kB 3*512kB 3*1024kB 1*2048kB 0*4096kB = 8056kB Node 0 DMA32: 422*4kB 0*8kB 0*16kB 3*32kB 1*64kB 1*128kB 0*256kB 1*512kB 1*1024kB 1*2048kB 0*4096kB = 5560kB 1914 total pagecache pages 106 pages in swap cache Swap cache stats: add 499740, delete 499634, find 61395/208276 Free swap = 4177680kB Total swap = 4194300kB 524224 pages RAM 79718 pages reserved 1622 pages shared 438890 pages non-shared Out of memory: kill process 2672 (sshd) score 2515 or a child Killed process 3013 (sshd) vsz:97340kB, anon-rss:0kB, file-rss:4kB postmark used greatest stack depth: 2560 bytes left I identified one potential leak, on an error path, through code inspection but I still hit OOM even with the following patch: --- block/blk-core.c | 24 ++++++++++++++++++++++++ drivers/scsi/sd.c | 9 ++++++++- include/linux/blkdev.h | 1 + 3 files changed, 33 insertions(+), 1 deletion(-) Index: linux-2.6/drivers/scsi/sd.c =================================================================== --- linux-2.6.orig/drivers/scsi/sd.c +++ linux-2.6/drivers/scsi/sd.c @@ -424,6 +424,7 @@ static int scsi_setup_discard_cmnd(struc sector_t sector = bio->bi_sector; unsigned int nr_sectors = bio_sectors(bio); unsigned int len; + int ret; struct page *page; if (sdkp->device->sector_size == 4096) { @@ -464,7 +465,13 @@ static int scsi_setup_discard_cmnd(struc } blk_add_request_payload(rq, page, len); - return scsi_setup_blk_pc_cmnd(sdp, rq); + ret = scsi_setup_blk_pc_cmnd(sdp, rq); + if (ret != BLKPREP_OK) { + blk_clear_request_payload(rq); + __free_page(page); + } + + return ret; } /** Index: linux-2.6/block/blk-core.c =================================================================== --- linux-2.6.orig/block/blk-core.c +++ linux-2.6/block/blk-core.c @@ -1139,6 +1139,30 @@ void blk_add_request_payload(struct requ } EXPORT_SYMBOL_GPL(blk_add_request_payload); +/** + * blk_add_request_payload - add a payload to a request + * @rq: request to update + * + * This clears a request's payload. The driver needs to take care of + * freeing the payload itself. + */ +void blk_clear_request_payload(struct request *rq) +{ + struct bio *bio = rq->bio; + + rq->__data_len = rq->resid_len = 0; + rq->nr_phys_segments = 0; + rq->buffer = NULL; + + bio->bi_size = 0; + bio->bi_vcnt = 0; + bio->bi_phys_segments = 0; + + bio->bi_io_vec->bv_page = NULL; + bio->bi_io_vec->bv_len = 0; +} +EXPORT_SYMBOL_GPL(blk_clear_request_payload); + void init_request_from_bio(struct request *req, struct bio *bio) { req->cpu = bio->bi_comp_cpu; Index: linux-2.6/include/linux/blkdev.h =================================================================== --- linux-2.6.orig/include/linux/blkdev.h +++ linux-2.6/include/linux/blkdev.h @@ -779,6 +779,7 @@ extern void blk_insert_request(struct re extern void blk_requeue_request(struct request_queue *, struct request *); extern void blk_add_request_payload(struct request *rq, struct page *page, unsigned int len); +extern void blk_clear_request_payload(struct request *rq); extern int blk_rq_check_limits(struct request_queue *q, struct request *rq); extern int blk_lld_busy(struct request_queue *q); extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,