[libvirt] [PATCH v3 2/2] Storage : Fix cloning of raw, sparse volumes
Ján Tomko
jtomko at redhat.com
Fri Jul 3 13:54:31 UTC 2015
On Fri, Jun 26, 2015 at 05:13:26PM +0530, Prerna Saxena wrote:
> When virsh vol-clone is attempted on a raw file where capacity > allocation,
> the resulting cloned volume has a size that matches the virtual-size of
> the parent; in place of matching its actual, disk size.
> This patch fixes the cloned disk to have same _allocated_size_ as
> the parent file from which it was cloned.
>
> Ref: http://www.redhat.com/archives/libvir-list/2015-May/msg00050.html
>
> Also fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1130739
>
> Signed-off-by: Prerna Saxena <prerna at linux.vnet.ibm.com>
> ---
> src/storage/storage_backend.c | 23 ++++++++++-------------
> src/storage/storage_driver.c | 5 -----
> 2 files changed, 10 insertions(+), 18 deletions(-)
>
> diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
> index ce59f63..492b344 100644
> --- a/src/storage/storage_backend.c
> +++ b/src/storage/storage_backend.c
> @@ -342,7 +342,7 @@ virStorageBackendCreateBlockFrom(virConnectPtr conn ATTRIBUTE_UNUSED,
> goto cleanup;
> }
>
> - remain = vol->target.allocation;
> + remain = vol->target.capacity;
>
> if (inputvol) {
> int res = virStorageBackendCopyToFD(vol, inputvol,
> @@ -397,7 +397,8 @@ createRawFile(int fd, virStorageVolDefPtr vol,
> virStorageVolDefPtr inputvol,
> bool reflink_copy)
> {
> - bool need_alloc = true;
> + bool want_sparse = (inputvol &&
> + (inputvol->target.capacity > vol->target.allocation));
> int ret = 0;
> unsigned long long remain;
>
> @@ -420,10 +421,9 @@ createRawFile(int fd, virStorageVolDefPtr vol,
> * 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 (vol->target.allocation) {
> - if (fallocate(fd, 0, 0, vol->target.allocation) == 0) {
> - need_alloc = false;
> - } else if (errno != ENOSYS && errno != EOPNOTSUPP) {
> + if (vol->target.allocation && !want_sparse) {
> + if ((fallocate(fd, 0, 0, vol->target.allocation) != 0) &&
If fallocate succeeds here, there's no need to copy zero bytes from the
source.
> + (errno != ENOSYS && errno != EOPNOTSUPP)) {
> ret = -errno;
> virReportSystemError(errno,
> _("cannot allocate %llu bytes in file '%s'"),
> @@ -433,22 +433,19 @@ createRawFile(int fd, virStorageVolDefPtr vol,
> }
> #endif
>
> - remain = vol->target.allocation;
> + remain = vol->target.capacity;
>
This breaks sparse file creation on systems without fallocate.
> if (inputvol) {
> /* allow zero blocks to be skipped if we've requested sparse
> - * allocation (allocation < capacity) or we have already
> - * been able to allocate the required space. */
> - bool want_sparse = !need_alloc ||
> - (vol->target.allocation < inputvol->target.capacity);
> -
> + * allocation (allocation < capacity)
> + */
> ret = virStorageBackendCopyToFD(vol, inputvol, fd, &remain,
> want_sparse, reflink_copy);
I'd rahter use !need_alloc instead of want_sparse here, because
sparseness only makes sense for cloning volumes, but the bool affects
creating new volumes as well.
> if (ret < 0)
> goto cleanup;
> }
>
> - if (remain && need_alloc) {
> + if (remain && !want_sparse) {
> if (safezero(fd, vol->target.allocation - remain, remain) < 0) {
This calculation assumes that 'remain' contains the bytes remaining to
the target allocation, but after this patch it contains the bytes
remaining to the target capacity.
> ret = -errno;
> virReportSystemError(errno, _("cannot fill file '%s'"),
I'll send a v4 shortly.
Jan
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