Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Thu 31 Aug 2017 09:21:49 BST
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  qcow2: allocate cluster_cache/cluster_data on demand
  qemu-doc: Add UUID support in initiator name
  tests: migration/guestperf Python 2.6 argparse compatibility
  docker.py: Python 2.6 argparse compatibility
  scripts: add argparse module for Python 2.6 compatibility
  misc: Remove unused Error variables
  oslib-posix: Print errors before aborting on qemu_alloc_stack()
  throttle: Test the valid range of config values
  throttle: Make burst_length 64bit and add range checks
  throttle: Make LeakyBucket.avg and LeakyBucket.max integer types
  throttle: Remove throttle_fix_bucket() / throttle_unfix_bucket()
  throttle: Make throttle_is_valid() a bit less verbose
  throttle: Update the throttle_fix_bucket() documentation
  throttle: Fix wrong variable name in the header documentation
  nvme: Fix get/set number of queues feature, again

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index f06c08f64c..8538533102 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1516,6 +1516,23 @@ int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset)
         nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask) + 1;
         sector_offset = coffset & 511;
         csize = nb_csectors * 512 - sector_offset;
+
+        /* Allocate buffers on first decompress operation, most images are
+         * uncompressed and the memory overhead can be avoided.  The buffers
+         * are freed in .bdrv_close().
+         */
+        if (!s->cluster_data) {
+            /* one more sector for decompressed data alignment */
+            s->cluster_data = qemu_try_blockalign(bs->file->bs,
+                    QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size + 512);
+            if (!s->cluster_data) {
+                return -ENOMEM;
+            }
+        }
+        if (!s->cluster_cache) {
+            s->cluster_cache = g_malloc(s->cluster_size);
+        }
+
         BLKDBG_EVENT(bs->file, BLKDBG_READ_COMPRESSED);
         ret = bdrv_read(bs->file, coffset >> 9, s->cluster_data,
                         nb_csectors);