From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759890AbZIQR5q (ORCPT ); Thu, 17 Sep 2009 13:57:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758877AbZIQR5p (ORCPT ); Thu, 17 Sep 2009 13:57:45 -0400 Received: from verein.lst.de ([213.95.11.210]:60502 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758735AbZIQR5o (ORCPT ); Thu, 17 Sep 2009 13:57:44 -0400 Date: Thu, 17 Sep 2009 19:57:42 +0200 From: Christoph Hellwig To: rusty@rustcorp.com.au Cc: linux-kernel@vger.kernel.org Subject: [PATCH] virtio-blk: add support for cache flush Message-ID: <20090917175742.GA2416@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 () UPPERCASE_25_50 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Recent qemu has added a VIRTIO_BLK_F_FLUSH flag to advertise that the virtual disk has a volatile write cache that needs to be flushed. In case we see this feature implement tell the Linux block layer about the fact and use the new VIRTIO_BLK_T_FLUSH to flush the cache when required. This allows for an correct and simple implementation of write barriers. Signed-off-by: Christoph Hellwig Index: linux-2.6/drivers/block/virtio_blk.c =================================================================== --- linux-2.6.orig/drivers/block/virtio_blk.c 2009-09-17 14:31:58.269278765 -0300 +++ linux-2.6/drivers/block/virtio_blk.c 2009-09-17 14:32:43.228031777 -0300 @@ -91,15 +91,26 @@ static bool do_req(struct request_queue return false; vbr->req = req; - if (blk_fs_request(vbr->req)) { + switch (req->cmd_type) { + case REQ_TYPE_FS: vbr->out_hdr.type = 0; vbr->out_hdr.sector = blk_rq_pos(vbr->req); vbr->out_hdr.ioprio = req_get_ioprio(vbr->req); - } else if (blk_pc_request(vbr->req)) { + break; + case REQ_TYPE_BLOCK_PC: vbr->out_hdr.type = VIRTIO_BLK_T_SCSI_CMD; vbr->out_hdr.sector = 0; vbr->out_hdr.ioprio = req_get_ioprio(vbr->req); - } else { + break; + case REQ_TYPE_LINUX_BLOCK: + if (req->cmd[0] == REQ_LB_OP_FLUSH) { + vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH; + vbr->out_hdr.sector = 0; + vbr->out_hdr.ioprio = req_get_ioprio(vbr->req); + break; + } + /*FALLTHRU*/ + default: /* We don't put anything else in the queue. */ BUG(); } @@ -199,6 +210,12 @@ out: return err; } +static void virtblk_prepare_flush(struct request_queue *q, struct request *req) +{ + req->cmd_type = REQ_TYPE_LINUX_BLOCK; + req->cmd[0] = REQ_LB_OP_FLUSH; +} + static int virtblk_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd, unsigned long data) { @@ -336,7 +353,10 @@ static int __devinit virtblk_probe(struc index++; /* If barriers are supported, tell block layer that queue is ordered */ - if (virtio_has_feature(vdev, VIRTIO_BLK_F_BARRIER)) + if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH)) + blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_DRAIN_FLUSH, + virtblk_prepare_flush); + else if (virtio_has_feature(vdev, VIRTIO_BLK_F_BARRIER)) blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL); /* If disk is read-only in the host, the guest should obey */ @@ -423,7 +443,7 @@ static struct virtio_device_id id_table[ static unsigned int features[] = { VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE, - VIRTIO_BLK_F_SCSI, VIRTIO_BLK_F_IDENTIFY + VIRTIO_BLK_F_SCSI, VIRTIO_BLK_F_IDENTIFY, VIRTIO_BLK_F_FLUSH }; /* Index: linux-2.6/include/linux/virtio_blk.h =================================================================== --- linux-2.6.orig/include/linux/virtio_blk.h 2009-09-02 08:37:31.460714184 -0300 +++ linux-2.6/include/linux/virtio_blk.h 2009-09-17 14:32:03.245004201 -0300 @@ -17,6 +17,7 @@ #define VIRTIO_BLK_F_BLK_SIZE 6 /* Block size of disk is available*/ #define VIRTIO_BLK_F_SCSI 7 /* Supports scsi command passthru */ #define VIRTIO_BLK_F_IDENTIFY 8 /* ATA IDENTIFY supported */ +#define VIRTIO_BLK_F_FLUSH 9 /* Cache flush command support */ #define VIRTIO_BLK_ID_BYTES (sizeof(__u16[256])) /* IDENTIFY DATA */ @@ -38,6 +39,17 @@ struct virtio_blk_config { __u8 identify[VIRTIO_BLK_ID_BYTES]; } __attribute__((packed)); +/* + * Command types + * + * Usage is a bit tricky as some bits are used as flags and some are not. + * + * Rules: + * VIRTIO_BLK_T_OUT may be combinaed with VIRTIO_BLK_T_SCSI_CMD or + * VIRTIO_BLK_T_BARRIER. VIRTIO_BLK_T_FLUSH is a command of it's own + * and may no be comined with any of the other flags. + */ + /* These two define direction. */ #define VIRTIO_BLK_T_IN 0 #define VIRTIO_BLK_T_OUT 1 @@ -45,6 +57,9 @@ struct virtio_blk_config { /* This bit says it's a scsi command, not an actual read or write. */ #define VIRTIO_BLK_T_SCSI_CMD 2 +/* Cache flush command */ +#define VIRTIO_BLK_T_FLUSH 4 + /* Barrier before this op. */ #define VIRTIO_BLK_T_BARRIER 0x80000000