On Mon, May 04, 2009 at 01:43:02PM -0400, Cole Robinson wrote:
Add an extra 'inputvol' parameter to the file volume building routines. This allows us to easily reuse the duplicate functionality.
@@ -1032,15 +1046,68 @@ static int createRaw(virConnectPtr conn, virReportSystemError(conn, errno, _("cannot extend file '%s'"), vol->target.path); - close(fd); - return -1; + goto cleanup; + } + + remain = vol->capacity; + + if (inputfd != -1) { + size_t bytes = 1024 * 1024; + int sparse_interval = 512; + int amtread = -1; + + while (amtread != 0) { + char buf[bytes];
Preferrable not to allocate 1 MB on the stack, since not all OS default to such large stacks as Linux does for threads.
+ char *tmp; + int newamt; + + if (remain < bytes) + bytes = remain; + + if ((amtread = saferead(inputfd, buf, bytes)) < 0) { + virReportSystemError(conn, errno, + _("failed reading from file '%s'"), + inputvol->target.path); + goto cleanup; + } + remain -= amtread; + + /* Loop over amt read in 512 byte increments, looking for sparse + * blocks */ + tmp = buf; + newamt = amtread; + do { + int interval = ((sparse_interval > newamt) ? newamt + : sparse_interval ); + int sparse_counter = interval; + + while (sparse_counter-- && *(tmp+sparse_counter) == '\0') + continue; + + if (sparse_counter < 0) { + if (lseek(fd, interval, SEEK_CUR) < 0) { + virReportSystemError(conn, errno, + _("cannot extend file '%s'"), + vol->target.path); + goto cleanup; + } + } else if (safewrite(fd, tmp, interval) < 0) { + virReportSystemError(conn, errno, + _("failed writing to file '%s'"), + vol->target.path); + goto cleanup; + + } + + tmp += interval; + } while ((newamt -= sparse_interval) > 0); + }
I'm finding this bit of code a little hard to follow. Since you're scanning in fixed 512 byte chunks, how about just doing char buf[512]; memset(buf, 0, sizeof buf); and then just doing a simple loop using memcmp(tmp, buf) over the 1 MB data. Sure, the current code allows for detection of chunks of zeros < 512 in size, but since data is allocated in underlying FS in at least that size chunks, its not worth trying to detect zeros < 512 in length Regards, Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|