From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933591Ab0FRPAH (ORCPT ); Fri, 18 Jun 2010 11:00:07 -0400 Received: from verein.lst.de ([213.95.11.210]:47653 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933531Ab0FRPAF (ORCPT ); Fri, 18 Jun 2010 11:00:05 -0400 Date: Fri, 18 Jun 2010 16:59:42 +0200 From: Christoph Hellwig To: axboe@kernel.dk, snitzer@redhat.com Cc: martin.petersen@oracle.com, James.Bottomley@suse.de, linux-kernel@vger.kernel.org Subject: [PATCH, RFC] block: don't allocate a payload for discard request Message-ID: <20100618145942.GA1148@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.28i X-Spam-Score: 0 () Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Index: linux-2.6/block/blk-lib.c =================================================================== --- linux-2.6.orig/block/blk-lib.c 2010-06-18 11:33:37.313260457 +0200 +++ linux-2.6/block/blk-lib.c 2010-06-18 16:49:20.854319055 +0200 @@ -19,7 +19,6 @@ static void blkdev_discard_end_io(struct if (bio->bi_private) complete(bio->bi_private); - __free_page(bio_page(bio)); bio_put(bio); } @@ -43,7 +42,6 @@ int blkdev_issue_discard(struct block_de int type = flags & BLKDEV_IFL_BARRIER ? DISCARD_BARRIER : DISCARD_NOBARRIER; struct bio *bio; - struct page *page; int ret = 0; if (!q) @@ -53,35 +51,21 @@ int blkdev_issue_discard(struct block_de return -EOPNOTSUPP; while (nr_sects && !ret) { - unsigned int sector_size = q->limits.logical_block_size; unsigned int max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9); bio = bio_alloc(gfp_mask, 1); - if (!bio) - goto out; + if (!bio) { + ret = -ENOMEM; + break; + } + bio->bi_sector = sector; bio->bi_end_io = blkdev_discard_end_io; bio->bi_bdev = bdev; if (flags & BLKDEV_IFL_WAIT) bio->bi_private = &wait; - /* - * Add a zeroed one-sector payload as that's what - * our current implementations need. If we'll ever need - * more the interface will need revisiting. - */ - page = alloc_page(gfp_mask | __GFP_ZERO); - if (!page) - goto out_free_bio; - if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size) - goto out_free_page; - - /* - * And override the bio size - the way discard works we - * touch many more blocks on disk than the actual payload - * length. - */ if (nr_sects > max_discard_sectors) { bio->bi_size = max_discard_sectors << 9; nr_sects -= max_discard_sectors; @@ -103,13 +87,8 @@ int blkdev_issue_discard(struct block_de ret = -EIO; bio_put(bio); } + return ret; -out_free_page: - __free_page(page); -out_free_bio: - bio_put(bio); -out: - return -ENOMEM; } EXPORT_SYMBOL(blkdev_issue_discard); Index: linux-2.6/drivers/scsi/sd.c =================================================================== --- linux-2.6.orig/drivers/scsi/sd.c 2010-06-18 11:33:37.322253892 +0200 +++ linux-2.6/drivers/scsi/sd.c 2010-06-18 16:50:04.790255778 +0200 @@ -411,22 +411,25 @@ static void sd_prot_op(struct scsi_cmnd } /** - * sd_prepare_discard - unmap blocks on thinly provisioned device + * scsi_setup_discard_cmnd - unmap blocks on thinly provisioned device + * @sdp: scsi device to operate one * @rq: Request to prepare * * Will issue either UNMAP or WRITE SAME(16) depending on preference * indicated by target device. **/ -static int sd_prepare_discard(struct request *rq) +static int scsi_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq) { struct scsi_disk *sdkp = scsi_disk(rq->rq_disk); struct bio *bio = rq->bio; sector_t sector = bio->bi_sector; - unsigned int num = bio_sectors(bio); + unsigned int nr_sectors = bio_sectors(bio); + unsigned int len; + struct page *page; if (sdkp->device->sector_size == 4096) { sector >>= 3; - num >>= 3; + nr_sectors >>= 3; } rq->cmd_type = REQ_TYPE_BLOCK_PC; @@ -434,31 +437,35 @@ static int sd_prepare_discard(struct req memset(rq->cmd, 0, rq->cmd_len); + page = alloc_page(GFP_ATOMIC | __GFP_ZERO); + if (!page) + return BLKPREP_DEFER; + if (sdkp->unmap) { - char *buf = kmap_atomic(bio_page(bio), KM_USER0); + char *buf = page_address(page); + rq->cmd_len = 10; rq->cmd[0] = UNMAP; rq->cmd[8] = 24; - rq->cmd_len = 10; - - /* Ensure that data length matches payload */ - rq->__data_len = bio->bi_size = bio->bi_io_vec->bv_len = 24; put_unaligned_be16(6 + 16, &buf[0]); put_unaligned_be16(16, &buf[2]); put_unaligned_be64(sector, &buf[8]); - put_unaligned_be32(num, &buf[16]); + put_unaligned_be32(nr_sectors, &buf[16]); - kunmap_atomic(buf, KM_USER0); + len = 24; } else { + rq->cmd_len = 16; rq->cmd[0] = WRITE_SAME_16; rq->cmd[1] = 0x8; /* UNMAP */ put_unaligned_be64(sector, &rq->cmd[2]); - put_unaligned_be32(num, &rq->cmd[10]); - rq->cmd_len = 16; + put_unaligned_be32(nr_sectors, &rq->cmd[10]); + + len = sdkp->device->sector_size; } - return BLKPREP_OK; + blk_add_request_payload(rq, page, len); + return scsi_setup_blk_pc_cmnd(sdp, rq); } /** @@ -485,10 +492,10 @@ static int sd_prep_fn(struct request_que * Discard request come in as REQ_TYPE_FS but we turn them into * block PC requests to make life easier. */ - if (rq->cmd_flags & REQ_DISCARD) - ret = sd_prepare_discard(rq); - - if (rq->cmd_type == REQ_TYPE_BLOCK_PC) { + if (rq->cmd_flags & REQ_DISCARD) { + ret = scsi_setup_discard_cmnd(sdp, rq); + goto out; + } else if (rq->cmd_type == REQ_TYPE_BLOCK_PC) { ret = scsi_setup_blk_pc_cmnd(sdp, rq); goto out; } else if (rq->cmd_type != REQ_TYPE_FS) { @@ -1163,6 +1170,15 @@ static int sd_done(struct scsi_cmnd *SCp int sense_valid = 0; int sense_deferred = 0; + /* + * If this is a discard request that originated from the kernel + * we need to free our payload here. Note that we need to check + * the request flag as the normal payload rules apply for + * pass-through UNMAP / WRITE SAME requests. + */ + if (SCpnt->request->cmd_flags & REQ_DISCARD) + __free_page(bio_page(SCpnt->request->bio)); + if (result) { sense_valid = scsi_command_normalize_sense(SCpnt, &sshdr); if (sense_valid) Index: linux-2.6/block/blk-core.c =================================================================== --- linux-2.6.orig/block/blk-core.c 2010-06-18 16:43:23.711273168 +0200 +++ linux-2.6/block/blk-core.c 2010-06-18 16:48:17.392256056 +0200 @@ -1135,6 +1135,38 @@ void blk_put_request(struct request *req } EXPORT_SYMBOL(blk_put_request); +/** + * blk_add_request_payload - add a payload to a request + * @rq: request to update + * @page: page backing the payload + * @len: length of the payload. + * + * This allows to later add a payload to an already submitted request by + * a block driver. The driver needs to take care of freeing the payload + * itself. + * + * Note that this is a quite horrible hack and nothing but handling of + * discard requests should ever use it. + */ +void blk_add_request_payload(struct request *rq, struct page *page, + unsigned int len) +{ + struct bio *bio = rq->bio; + + bio->bi_io_vec->bv_page = page; + bio->bi_io_vec->bv_offset = 0; + bio->bi_io_vec->bv_len = len; + + bio->bi_size = len; + bio->bi_vcnt = 1; + bio->bi_phys_segments = 1; + + rq->__data_len = rq->resid_len = len; + rq->nr_phys_segments = 1; + rq->buffer = bio_data(bio); +} +EXPORT_SYMBOL_GPL(blk_add_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 2010-06-18 16:45:29.223003718 +0200 +++ linux-2.6/include/linux/blkdev.h 2010-06-18 16:47:25.894005813 +0200 @@ -702,6 +702,8 @@ extern struct request *blk_make_request( gfp_t); extern void blk_insert_request(struct request_queue *, struct request *, int, void *); 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 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,