[libvirt] [PATCH] storage_backend: Fix issue with allocation of 0 length volume

Commit id '532fef36' added a call to fallocate() and some error handling based on whether or not the function existed. This new call resulted in libvirt-cim/cimtest failures when attempting to create a volume with "0" (zero) allocation value. The failure is logged as: Oct 9 07:51:33 localhost libvirtd[8030]: cannot allocate 0 bytes in file '/var/lib/libvirt/images/cimtest-vol.img': Invalid argument This can also be seen with virsh vol-create-as: error: Failed to create vol test error: cannot allocate 0 bytes in file '/home/vm-images/test': Invalid argument error: Failed to create vol test error: cannot allocate 0 bytes in file '/home/vm-images/test': Invalid argument It turns out fallocate() will return EINVAL when the incoming 'len' (or allocation) value is 0 (or less). --- src/storage/storage_backend.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c index 662af32..d0580f9 100644 --- a/src/storage/storage_backend.c +++ b/src/storage/storage_backend.c @@ -332,19 +332,22 @@ createRawFile(int fd, virStorageVolDefPtr vol, /* Avoid issues with older kernel's <linux/fs.h> namespace pollution. */ #if HAVE_FALLOCATE - 0 /* Try to preallocate all requested disk space, but fall back to - * other methods if this fails with ENOSYS or EOPNOTSUPP. + * other methods if this fails with ENOSYS or EOPNOTSUPP. If allocation + * is 0 (or less than 0), then fallocate will fail with EINVAL. * NOTE: do not use posix_fallocate; posix_fallocate falls back * to writing zeroes block by block in case fallocate isn't * available, and since we're going to copy data from another * file it doesn't make sense to write the file twice. */ - if (fallocate(fd, 0, 0, vol->allocation) == 0) { - need_alloc = 0; - } else if (errno != ENOSYS && errno != EOPNOTSUPP) { - ret = -errno; - virReportSystemError(errno, - _("cannot allocate %llu bytes in file '%s'"), - vol->allocation, vol->target.path); - goto cleanup; + if (vol->allocation) { + if (fallocate(fd, 0, 0, vol->allocation) == 0) { + need_alloc = 0; + } else if (errno != ENOSYS && errno != EOPNOTSUPP) { + ret = -errno; + virReportSystemError(errno, + _("cannot allocate %llu bytes in file '%s'"), + vol->allocation, vol->target.path); + goto cleanup; + } } #endif -- 1.8.3.1