Am 05.06.2014 um 16:52 hat Benoît Canet geschrieben:
> The Thursday 05 Jun 2014 à 15:36:23 (+0200), Kevin Wolf wrote :
> > Some code in the block layer makes potentially huge allocations. Failure
> > is not completely unexpected there, so avoid aborting qemu and handle
> > out-of-memory situations gracefully.
> >
> > This patch addresses the allocations in the qcow2 block driver.
> >
> > Signed-off-by: Kevin Wolf <kw...@redhat.com>
> > Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
> > ---
> > block/qcow2-cache.c | 13 ++++++++++++-
> > block/qcow2-cluster.c | 35 +++++++++++++++++++++++++++--------
> > block/qcow2-refcount.c | 48
> > ++++++++++++++++++++++++++++++++++++++----------
> > block/qcow2-snapshot.c | 22 +++++++++++++++++-----
> > block/qcow2.c | 41 +++++++++++++++++++++++++++++++++--------
> > 5 files changed, 127 insertions(+), 32 deletions(-)
> > @@ -1562,7 +1574,10 @@ static int
> > expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
> > if (!is_active_l1) {
> > /* inactive L2 tables require a buffer to be stored in when loading
> > * them from disk */
> > - l2_table = qemu_blockalign(bs, s->cluster_size);
> > + l2_table = qemu_try_blockalign(bs, s->cluster_size);
> > + if (l2_table == NULL) {
> > + return -ENOMEM;
> > + }
> > }
> >
> > for (i = 0; i < l1_size; i++) {
> > @@ -1740,7 +1755,11 @@ int qcow2_expand_zero_clusters(BlockDriverState *bs)
> >
> > nb_clusters = size_to_clusters(s, bs->file->total_sectors *
> > BDRV_SECTOR_SIZE);
> I think we need asset(nb_clusters >= 1); else it will trigger a spurious
> -ENOMEM
> on very small files.
To be precise, very small means size 0, because size_to_clusters() rounds
up. An image file with size 0 wouldn't have a qcow2 header, though, so we
wouldn't even have opened it in the first place.
(Also, an assert() never fixes a bug. At best, it changes its symptom to
a crash, except when built with NDEBUG defined.)
> > - expanded_clusters = g_malloc0((nb_clusters + 7) / 8);
> > + expanded_clusters = g_try_malloc0((nb_clusters + 7) / 8);
> > + if (expanded_clusters == NULL) {
> > + ret = -ENOMEM;
> > + goto fail;
> > + }
> >
> > ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size,
> > &expanded_clusters, &nb_clusters);
Kevin
