From patchwork Tue Jun 14 18:18:20 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 100424 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [140.186.70.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 10BA2B6F7C for ; Wed, 15 Jun 2011 05:15:12 +1000 (EST) Received: from localhost ([::1]:41436 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWZ4u-0002KJ-AJ for incoming@patchwork.ozlabs.org; Tue, 14 Jun 2011 15:15:08 -0400 Received: from eggs.gnu.org ([140.186.70.92]:38412) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWYCh-00061Z-DB for qemu-devel@nongnu.org; Tue, 14 Jun 2011 14:19:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QWYCf-0006I9-1a for qemu-devel@nongnu.org; Tue, 14 Jun 2011 14:19:06 -0400 Received: from mtagate3.uk.ibm.com ([194.196.100.163]:41635) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWYCe-00068E-Gx for qemu-devel@nongnu.org; Tue, 14 Jun 2011 14:19:04 -0400 Received: from d06nrmr1806.portsmouth.uk.ibm.com (d06nrmr1806.portsmouth.uk.ibm.com [9.149.39.193]) by mtagate3.uk.ibm.com (8.13.1/8.13.1) with ESMTP id p5EIIkwT013482 for ; Tue, 14 Jun 2011 18:18:46 GMT Received: from d06av12.portsmouth.uk.ibm.com (d06av12.portsmouth.uk.ibm.com [9.149.37.247]) by d06nrmr1806.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5EIIfiJ2425050 for ; Tue, 14 Jun 2011 19:18:46 +0100 Received: from d06av12.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av12.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5EIIfEP014727 for ; Tue, 14 Jun 2011 12:18:41 -0600 Received: from stefanha-thinkpad.ibm.com (sig-9-145-202-176.de.ibm.com [9.145.202.176]) by d06av12.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id p5EIIdDj014627; Tue, 14 Jun 2011 12:18:40 -0600 From: Stefan Hajnoczi To: Date: Tue, 14 Jun 2011 19:18:20 +0100 Message-Id: <1308075511-4745-3-git-send-email-stefanha@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.5.3 In-Reply-To: <1308075511-4745-1-git-send-email-stefanha@linux.vnet.ibm.com> References: <1308075511-4745-1-git-send-email-stefanha@linux.vnet.ibm.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6, seldom 2.4 (older, 4) X-Received-From: 194.196.100.163 Cc: Kevin Wolf , Anthony Liguori , Stefan Hajnoczi , Adam Litke Subject: [Qemu-devel] [PATCH 02/13] block: add -drive copy-on-read=on|off X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org This patch adds the -drive copy-on-read=on|off command-line option: copy-on-read=on|off copy-on-read is "on" or "off" and enables whether to copy read backing file sectors into the image file. Copy-on-read avoids accessing the same backing file sectors repeatedly and is useful when the backing file is over a slow network. By default copy-on-read is off. The new BlockDriverState.copy_on_read field indicates whether copy-on-read is enabled. Block drivers can use this as a hint to copy sectors read from the backing file into the image file. The point of copy-on-read is to avoid accessing the backing file again in the future. Signed-off-by: Stefan Hajnoczi --- block.c | 5 +++++ block.h | 1 + block_int.h | 1 + blockdev.c | 6 ++++++ hmp-commands.hx | 5 +++-- qemu-config.c | 3 +++ qemu-options.hx | 9 ++++++++- 7 files changed, 27 insertions(+), 3 deletions(-) diff --git a/block.c b/block.c index 24a25d5..99068c9 100644 --- a/block.c +++ b/block.c @@ -430,6 +430,11 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename, /* buffer_alignment defaulted to 512, drivers can change this value */ bs->buffer_alignment = 512; + bs->copy_on_read = 0; + if (flags & BDRV_O_RDWR) { + bs->copy_on_read = !!(flags & BDRV_O_COPY_ON_READ); + } + pstrcpy(bs->filename, sizeof(bs->filename), filename); if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv)) { diff --git a/block.h b/block.h index da7d39c..deb19ec 100644 --- a/block.h +++ b/block.h @@ -34,6 +34,7 @@ typedef struct QEMUSnapshotInfo { #define BDRV_O_NATIVE_AIO 0x0080 /* use native AIO instead of the thread pool */ #define BDRV_O_NO_BACKING 0x0100 /* don't open the backing file */ #define BDRV_O_NO_FLUSH 0x0200 /* disable flushing on this disk */ +#define BDRV_O_COPY_ON_READ 0x0400 /* copy read backing sectors into image */ #define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH) diff --git a/block_int.h b/block_int.h index fa91337..135625a 100644 --- a/block_int.h +++ b/block_int.h @@ -152,6 +152,7 @@ struct BlockDriverState { int encrypted; /* if true, the media is encrypted */ int valid_key; /* if true, a valid encryption key has been set */ int sg; /* if true, the device is a /dev/sg* */ + int copy_on_read; /* if true, copy read backing sectors into image */ /* event callback when inserting/removing */ void (*change_cb)(void *opaque, int reason); void *change_opaque; diff --git a/blockdev.c b/blockdev.c index 1502575..9dbd2fa 100644 --- a/blockdev.c +++ b/blockdev.c @@ -237,6 +237,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi) const char *devaddr; DriveInfo *dinfo; int snapshot = 0; + int copy_on_read; int ret; translation = BIOS_ATA_TRANSLATION_AUTO; @@ -261,6 +262,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi) snapshot = qemu_opt_get_bool(opts, "snapshot", 0); ro = qemu_opt_get_bool(opts, "readonly", 0); + copy_on_read = qemu_opt_get_bool(opts, "copy-on-read", 0); file = qemu_opt_get(opts, "file"); serial = qemu_opt_get(opts, "serial"); @@ -521,6 +523,10 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi) bdrv_flags |= (BDRV_O_SNAPSHOT|BDRV_O_CACHE_WB|BDRV_O_NO_FLUSH); } + if (copy_on_read) { + bdrv_flags |= BDRV_O_COPY_ON_READ; + } + if (media == MEDIA_CDROM) { /* CDROM is fine for any interface, don't check. */ ro = 1; diff --git a/hmp-commands.hx b/hmp-commands.hx index 6ad8806..f6cc724 100644 --- a/hmp-commands.hx +++ b/hmp-commands.hx @@ -863,9 +863,10 @@ ETEXI .args_type = "pci_addr:s,opts:s", .params = "[[:]:]\n" "[file=file][,if=type][,bus=n]\n" - "[,unit=m][,media=d][index=i]\n" + "[,unit=m][,media=d][,index=i]\n" "[,cyls=c,heads=h,secs=s[,trans=t]]\n" - "[snapshot=on|off][,cache=on|off]", + "[,snapshot=on|off][,cache=on|off]\n" + "[,readonly=on|off][,copy-on-read=on|off]", .help = "add drive to PCI storage controller", .mhandler.cmd = drive_hot_add, }, diff --git a/qemu-config.c b/qemu-config.c index 7558fa8..dafacb7 100644 --- a/qemu-config.c +++ b/qemu-config.c @@ -78,6 +78,9 @@ static QemuOptsList qemu_drive_opts = { }, { .name = "readonly", .type = QEMU_OPT_BOOL, + }, { + .name = "copy-on-read", + .type = QEMU_OPT_BOOL, }, { /* end of list */ } }, diff --git a/qemu-options.hx b/qemu-options.hx index f2ef9a1..97abcd9 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -120,7 +120,7 @@ DEF("drive", HAS_ARG, QEMU_OPTION_drive, " [,cyls=c,heads=h,secs=s[,trans=t]][,snapshot=on|off]\n" " [,cache=writethrough|writeback|none|unsafe][,format=f]\n" " [,serial=s][,addr=A][,id=name][,aio=threads|native]\n" - " [,readonly=on|off]\n" + " [,readonly=on|off][,copy-on-read=on|off]\n" " use 'file' as a drive image\n", QEMU_ARCH_ALL) STEXI @item -drive @var{option}[,@var{option}[,@var{option}[,...]]] @@ -160,6 +160,9 @@ an untrusted format header. This option specifies the serial number to assign to the device. @item addr=@var{addr} Specify the controller's PCI address (if=virtio only). +@item copy-on-read=@var{copy-on-read} +@var{copy-on-read} is "on" or "off" and enables whether to copy read backing +file sectors into the image file. @end table By default, writethrough caching is used for all block device. This means that @@ -187,6 +190,10 @@ like your host losing power, the disk storage getting disconnected accidently, etc. you're image will most probably be rendered unusable. When using the @option{-snapshot} option, unsafe caching is always used. +Copy-on-read avoids accessing the same backing file sectors repeatedly and is +useful when the backing file is over a slow network. By default copy-on-read +is off. + Instead of @option{-cdrom} you can use: @example qemu -drive file=file,index=2,media=cdrom