From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=60555 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q2S3h-0001tt-Rd for qemu-devel@nongnu.org; Wed, 23 Mar 2011 13:41:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q2S3g-0003sF-Gg for qemu-devel@nongnu.org; Wed, 23 Mar 2011 13:41:25 -0400 Received: from mtagate2.uk.ibm.com ([194.196.100.162]:36391) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q2S3g-0003rg-9X for qemu-devel@nongnu.org; Wed, 23 Mar 2011 13:41:24 -0400 Received: from d06nrmr1507.portsmouth.uk.ibm.com (d06nrmr1507.portsmouth.uk.ibm.com [9.149.38.233]) by mtagate2.uk.ibm.com (8.13.1/8.13.1) with ESMTP id p2NHfMbt022464 for ; Wed, 23 Mar 2011 17:41:22 GMT Received: from d06av10.portsmouth.uk.ibm.com (d06av10.portsmouth.uk.ibm.com [9.149.37.251]) by d06nrmr1507.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p2NHfol21933330 for ; Wed, 23 Mar 2011 17:41:50 GMT Received: from d06av10.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av10.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p2NHfLKt016822 for ; Wed, 23 Mar 2011 11:41:22 -0600 From: Stefan Hajnoczi Date: Wed, 23 Mar 2011 17:40:54 +0000 Message-Id: <1300902055-25850-3-git-send-email-stefanha@linux.vnet.ibm.com> In-Reply-To: <1300902055-25850-1-git-send-email-stefanha@linux.vnet.ibm.com> References: <1300902055-25850-1-git-send-email-stefanha@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 2/3] block: Do not cache device size for removable media List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Amit Shah , Anthony Liguori , Ryan Harper , Stefan Hajnoczi The block layer caches the device size to avoid doing lseek(fd, 0, SEEK_END) every time this value is needed. For removable media the device size becomes stale if a new medium is inserted. This patch simply prevents device size caching for removable media. A smarter solution is to update the cached device size when a new medium is inserted. Given that there are currently bugs with CD-ROM media change I do not want to implement that approach until we've gotten things correct first. Signed-off-by: Stefan Hajnoczi --- block.c | 12 +++++------- 1 files changed, 5 insertions(+), 7 deletions(-) diff --git a/block.c b/block.c index 8f224b4..89f6ded 100644 --- a/block.c +++ b/block.c @@ -1153,14 +1153,12 @@ int64_t bdrv_getlength(BlockDriverState *bs) if (!drv) return -ENOMEDIUM; - /* Fixed size devices use the total_sectors value for speed instead of - issuing a length query (like lseek) on each call. Also, legacy block - drivers don't provide a bdrv_getlength function and must use - total_sectors. */ - if (!bs->growable || !drv->bdrv_getlength) { - return bs->total_sectors * BDRV_SECTOR_SIZE; - } - return drv->bdrv_getlength(bs); + if (bs->growable || bs->removable) { + if (drv->bdrv_getlength) { + return drv->bdrv_getlength(bs); + } + } + return bs->total_sectors * BDRV_SECTOR_SIZE; } /* return 0 as number of sectors if no device present or error */ -- 1.7.4.1