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 <stefa...@linux.vnet.ibm.com> --- block.c | 12 +++++------- 1 files changed, 5 insertions(+), 7 deletions(-) diff --git a/block.c b/block.c index f812c20..2bd353f 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