On Wed, Nov 23, 2011 at 8:58 AM, Stefan Hajnoczi <stefa...@gmail.com> wrote: > On Wed, Nov 23, 2011 at 4:42 AM, Zhi Yong Wu <zwu.ker...@gmail.com> wrote: >> On Thu, Nov 17, 2011 at 9:40 PM, Stefan Hajnoczi >> <stefa...@linux.vnet.ibm.com> wrote: >>> + /* Cover entire cluster so no additional backing file I/O is required >>> when >>> + * allocating cluster in the image file. >>> + */ >>> + round_to_clusters(bs, sector_num, nb_sectors, >>> + &cluster_sector_num, &cluster_nb_sectors); >> Why need to round down/up sector_num/nb_sectors in this function? The >> detection of race condition for write request has been done before >> this function. > > If we write less than a cluster then the image format will have to > perform additional to populate the regions of the cluster that we did
"perform additional I/O"
