From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=35928 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q7qUN-0005Sm-3A for qemu-devel@nongnu.org; Thu, 07 Apr 2011 10:47:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q7qUL-0004qV-51 for qemu-devel@nongnu.org; Thu, 07 Apr 2011 10:47:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36708) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q7qUK-0004py-Ks for qemu-devel@nongnu.org; Thu, 07 Apr 2011 10:47:12 -0400 From: Kevin Wolf Date: Thu, 7 Apr 2011 16:49:13 +0200 Message-Id: <1302187764-16421-5-git-send-email-kwolf@redhat.com> In-Reply-To: <1302187764-16421-1-git-send-email-kwolf@redhat.com> References: <1302187764-16421-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 04/15] 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: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: 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 Signed-off-by: Kevin Wolf --- block.c | 12 +++++------- 1 files changed, 5 insertions(+), 7 deletions(-) diff --git a/block.c b/block.c index d8da3b0..f731c7a 100644 --- a/block.c +++ b/block.c @@ -1161,14 +1161,12 @@ 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 */ -- 1.7.2.3