[libvirt] [PATCH] storage: only run safezero if allocation is > 0

[Martin Kletzander]

On Sun, Aug 23, 2015 at 10:14:29PM +0200, Guido Günther wrote:
>While a zero allocation in safezero should be fine it isn't when we use
>posix_fallocate which returns EINVAL on a zero allocation.
>
>While we could skip the zero allocation in safezero_posix_fallocate it's
>an optimization to do it for all allocations.
>
>This fixes vm installation via virtinst for me which otherwise aborts
>like:
>
>   Starting install...
>   Retrieving file linux...               | 5.9 MB     00:01 ...
>   Retrieving file initrd.gz...           |  29 MB     00:07 ...
>   ERROR    Couldn't create storage volume 'virtinst-linux.sBgds4': 'cannot fill file '/var/lib/libvirt/boot/virtinst-linux.sBgds4': Invalid argument'
>---
>No idea while this didn't show up earlier though.
>

ACK, that was probably caused due to previous unclean installation.

> src/storage/storage_backend.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
>index db49739..0418473 100644
>--- a/src/storage/storage_backend.c
>+++ b/src/storage/storage_backend.c
>@@ -455,7 +455,7 @@ createRawFile(int fd, virStorageVolDefPtr vol,
>         pos = inputvol->target.capacity - remain;
>     }
>
>-    if (need_alloc) {
>+    if (need_alloc && (vol->target.allocation - pos > 0)) {
>         if (safezero(fd, pos, vol->target.allocation - pos) < 0) {
>             ret = -errno;
>             virReportSystemError(errno, _("cannot fill file '%s'"),
>--
>2.1.4
>
>--
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